Comparing FF vs. APS-C

A long time ago, in a forum very very close.... Jon and I had a lengthy discussion [8-|] about comparing crop vs. FF sensors using lenses that correct for the crop factor (e.g. APS-C with 50/1.2L vs. FF with 85/1.8). The 'sequel' was a discussion with Rick, complete with example images reprocessed by Daniel, comparing the same lens on the 7D vs. 5DII, with the latter cropped to the APS-C angle of view. But, that didn't answer the question of comparing the two cameras with different lenses for taking the 'same' shot.


To satisfy my curiousity, I set up a simple test scene and shot it from the same distance with the 5DII + EF 135mm f/2<span style="color: #ff0000;"]Land the 7D + EF 85mm f/1.2<span style="color: #ff0000;"]LII (the latter having a FF-equivalence of 136mm f/1.92). One rationale for this is that these two combinations are two ways to achieve the same image (same FoV, DoF, and perspective). In our previous discussion (at which time I had the 7D and 85L, but not the 5DII or 135L), Jon's contention was that the FF body and the less expensive lens was the better choice (e.g. at current prices, 5DII+135L is $3600 while 7D+85L is $3850; the difference is more dramatic when comparing the 5DII+85/1.8 vs. the 7D+50L), and the FF body would deliver better IQ. He was right, and ultimately, that discussion was one reason why I added the 5DII to my kit.


Anyway, back to the comparison. Shots were taken wide open and at 2.5 and 5 stops narrower than the max aperture. The 5DII was shot as ISO 400, the 7D at ISO 200 (should have been ISO 160 on the 7D, actually, for the theoretical 1.3-stop difference to compensate for the effect of sensor size on noise - in practice, the 7D is relatively noisier than the 1.3-stop difference in sensor size predicts). Focus was manual with 10x Live View.


Minimal RAW processing was done in DPP to even out slight variations in color temperature and exposure - a custom WB was set using the dropper on a neutral square of theXrite ColorChecker Passport, andexposure was adjusted slightly so the clipping squares (brightest white on the ColorChecker) were all similarly exposed. Picture Style was set to Neutral, and all other corrections (ALO, peripheral illumination, etc.) were turned off.


The first composite shows the full image. The vignetting is evident wide open, and a bit worse with the 5DII + 135L, as you'd expect on a FF body compared to using an EF lens on a crop body.


[img]/cfs-file.ashx/__key/CommunityServer-Components-UserFiles/00-00-00-35-15/5DIIvs7D-Full-Image-Composite.jpg[/img]


The second composite is 100% crops from the center. No scaling was done, so the field of the crop is slightly larger with the 7D, due to the 14% lower megapixel count of the 7D (it's close enough that I think comparisons are possible without upscaling or downscaling both sets of images to the same final resolution). Sharpness and contrast are better across the board with the 5DII+135L. Both lenses improve a bit with stopping down.


[img]/cfs-file.ashx/__key/CommunityServer-Components-UserFiles/00-00-00-35-15/5DIIvs7D-Center-Composite.jpg[/img]


The final composite is100% crops from the upper left corner, with a SpyderCube there to provide a specular highlight and some text to judge sharpness. Wide open, the 7D+85L suffers from softer corners (even on crop) and really noticeable chromatic aberration, which is still evident even stopped down to f/2.8. The 7D's noise is also evident, even at ISO 200.


[img]/cfs-file.ashx/__key/CommunityServer-Components-UserFiles/00-00-00-35-15/5DIIvs7D-Upper-Left-Composite.jpg[/img]


So what have I learned? I've learned that I'm glad I have a 5DII - the IQ is excellent! I do like the flexibility of having the 5DII for portraits and landscapes, and the 7D for more reach and better AF for wildlife and birds. The 135L delivers better IQ than the 85L (consistent with reviews) - still, the 85L on FF is really an amazing and creative tool.


The other thing I've learned is that I'm tired of the New England run of rainy weather! I'd rather be outside shooting the world than indoors shooting test scenes. To that end, there's a break in the rain right now, and I've got my camera in the car, so I'm heading out to take some pictures. [:)]


--John

Great comparison John! Thanks for taking the time to set this up and share the results. Unfortunately, this makes me want a FF camera even more!


Stephen

John


Nice job.


There was really no surprise in your test. It is just as I thought it would be.


I wonder how the 1D IV would compare in a similar test. From hands on experience I think the difference in the5D II and the 1D IVmight be negligible.


Rick

Thanks, John, for that. It must have been a lot of work.


The 7D + 85 f/1.2 holds up much better better than I would have guessed. I still stand by everything I said before (the theory part), it's just that the 85 f1.2 is just far more wicked sharp in the center, even wide open, than I knew (I've since purchased an 85 f/1.2, so I'n not as surprised now as I would have been then). I still guess that ff + 135 f/2 is sharper, and if we had 60mp cameras, we would see a bigger difference. But who cares about that.

John,


Thanks for taking the time to perform the comparison. It is very interesting.[Y]


I am trying to decide how much of the quality difference is the lens vs the camera body. Am I right in thinking that much of the blur and CA is the lens but the noise is attributable to the body? I am really impressed by the smoothness of the 5DII, especially between the text. The 7D still looks good, but is noticeably noisier..


Good luck hunting today......it is nice that we've only had one deluge........I am hoping for tomorrow.


Thanks,


Brant

Thanks for the test, John. If it

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Originally Posted by Kayaker72

I am trying to decide how much of the quality difference is the lens vs the camera body.

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The body is allowing the 135 to operate at f/2 instead of f/1.2, and making the 135 pixels much bigger.


The CA is the fault of the lens, but using a crop body causes the CA to be magnified as compared to FF. On the other hand, lateral CA will show up more on the edges, which are cropped from the FF.

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Originally Posted by Kayaker72

The 7D still looks good, but is noticeably noisier..

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This is strange. In theory all things being equal there should be no difference in noise between FF and crop in this comparison. The 7D has a slightly less noisy sensor (less read noise), so I would have been sure the 7D would come out slightly ahead. Of course John is using ISO 200 instead of ISO160, but I still would have thought the difference between 5D and 7D to be almost zero.


Perhaps the difference has more to do with metering than anything else. To compare photon noise fairly, ISO isn't so important, but both cameras should have the same shutter speed (and ISO should be set to expose reasonably), so perhaps manual mode is best. John- were the shutter speeds similar?

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Originally Posted by Jon Ruyle

This is strange. In theory all things being equal there should be no difference in noise between FF and crop in this comparison. The 7D has a slightly less noisy sensor (less read noise), so I would have been sure the 7D would come out slightly ahead. Of course John is using ISO 200 instead of ISO160, but I still would have thought the difference between 5D and 7D to be almost zero.


Perhaps the difference has more to do with metering than anything else. To compare photon noise fairly, ISO isn't so important, but both cameras should have the same shutter speed (and ISO should be set to expose reasonably), so perhaps manual mode is best. John- were the shutter speeds similar?

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Jon


I kind of took the side by side test to be a comparison of equal DOF from both lenses and bodies. (F11 vs F6.7 or 6.7 x 1.6 to get to F11). I would think the 7D will have had a higher shutter speed to compensate for the difference. I am sure John will in lighten us.


But as for Noise, in theory it may or may not be true, but I have my own theories. The firmware writers at canon may not work in theory, but marketing. The 7D pictures have so much more room for improvement out of the camera compared to the 5D and 1D it is almost like canon dumbed the firmware down in the 7D so that it wouldn't be as competitive with its big brothers. (this is my conspiracy theory)

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Originally Posted by HDNitehawk

I would think the 7D will have had a higher shutter speed to compensate for the difference.

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The iso was different, too, to compensate.

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Originally Posted by HDNitehawk

The firmware writers at canon may not work in theory, but marketing. The 7D pictures have so much more room for improvement out of the camera compared to the 5D and 1D it is almost like canon dumbed the firmware down in the 7D so that it wouldn't be as competitive with its big brothers.

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According to DXO Mark's measurements, the 7D has a rating of 854. If you normalize this to full frame, you get 2156, compared with 1815 for the 5DII. Thus the 7D sensor is more sensitive. (And, according to what I've read, it has lower read noise as well.)


I admit, however, that these measured results may differ from real world impressions.

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Originally Posted by Jon Ruyle

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Originally Posted by HDNitehawk

I would think the 7D will have had a higher shutter speed to compensate for the difference.

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The iso was different, too, to compensate.

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I chose different ISO's in an attempt to compensate for the effect of sensor size on noise (and chose incorrectly by 1/3 stop). However, to try and keep things on relatively even footing, shutter speeds were kept constant as aperture changed, and were similar on the two cameras - to compensate for the narrower apertures, I increased Speedlite power. Here, too, I goofed...I simply used the C.Fn to set the sync speed to the max, meaning the 5DII shutter speed was 1/200 s throughout and the 7D was 1/250 s throughout - again, a 1/3-stop difference, but unfortunately in the same direction as my ISO choice.


So, in a way, I inadvertently stacked the noise deck in favor of the 5DII by 2/3 of a stop. Still, to me, there is more than 2/3 of a stop worth of extra noise in the 7D images. I'm starting to believe in Rick'sconspiracy theory... Looking at Bryan's noise tests in the 60D review, the 60D appears to have slightly less ISO noise(a subtle difference, but visible),even at lower ISOs, compared to the 7D. This may represent improved technology (despite the fact that the same sensor is used), or may be consistent with Rick'sconspiracy theory - they didn't have to dumb down 60D as much as the 7D in terms of ISO performance, because they dumbed it down in other ways (e.g. no AF microadjustment).

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Originally Posted by neuroanatomist

to compensate for the narrower apertures, I increased Speedlite power.

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You mean you gave the 5DII more light? Or do you mean you let the meter decide?


To make a fair comparison, each camera should get the same amount of light. So the shutter speed should be the same in ambient light, or the speedlight should be set to some fixed *equal* output value rather than relying on the meter. The 5DII will probably require a higher ISO to expose reasonably.


I don't think you stacked things in favor of the 5DII by using different shutter speeds, but if you let the meter decide, you ultimately allowed the meter of each camera to decide how much light to give the sensor. This could lead to a largeish difference one way or the other (I have no idea which way the bias would be, though)


If you told the flash to give the 5DII more light to compensate for the smaller aperture, you stacked the test heavily in favor of the 5DII. (I don't think you did this, though, because the 5DII would appear brighter if you had... after all, you already mostly compensated for the narrower aperture with ISO)


Unless the DXO Mark guys screwed up, the 7D should come out ahead in this comparison. It has lower read noise and lower photon noise.

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Originally Posted by Jon Ruyle

Unless the DXO Mark guys screwed up, the 7D should come out ahead in this comparison. It has lower read noise and lower photon noise.

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Jon


I haven't looked at the DXO guys data. But just from using the cameras I have it is very evident to me that in equal situations the 7D has more noise than the 5D II. As well the 1D IV has less than the 7D. The 1D IV seems to be close to the 5D II in this respect, but I can sense a slight edge with the 5D but not enough to notice or matter.


It might be worth looking at how DXO did their comparison to see if it is legitimate.

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Originally Posted by neuroanatomist

I chose different ISO's in an attempt to compensate for the effect of sensor size on noise (and chose incorrectly by 1/3 stop). However, to try and keep things on relatively even footing, shutter speeds were kept constant as aperture changed, and were similar on the two cameras - to compensate for the narrower apertures, I increased Speedlite power. Here, too, I goofed...I simply used the C.Fn to set the sync speed to the max, meaning the 5DII shutter speed was 1/200 s throughout and the 7D was 1/250 s throughout - again, a 1/3-stop difference, but unfortunately in the same direction as my ISO choice.


So, in a way, I inadvertently stacked the noise deck in favor of the 5DII by 2/3 of a stop. Still, to me, there is more than 2/3 of a stop worth of extra noise in the 7D images. I'm starting to believe in Rick'sconspiracy theory... Looking at Bryan's noise tests in the 60D review, the 60D appears to have slightly less ISO noise(a subtle difference, but visible),even at lower ISOs, compared to the 7D. This may represent improved technology (despite the fact that the same sensor is used), or may be consistent with Rick'sconspiracy theory - they didn't have to dumb down 60D as much as the 7D in terms of ISO performance, because they dumbed it down in other ways (e.g. no AF microadjustment

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John


I am not sure what a fair test would be considering the variables. At some point you are going to have to adjust either ISO or Shutter Speed or your Flash. Perhaps a comparison where you have no flash and equal lighting, and choose the shutter and ISO that you would choose for each camera in that situation. That would give you a true read of how that camera would perform with your own personal shooting style. For instance with the set up you used I might choose a moderate ISO and longer shutter speed because you are on a tripod shooting a static object. In the back of my mind though I suppose it would still be biased, because I wouldn't let the 7D ISO ever get as high as the 5D II. Still this wouldn't truly be a fair comparison, because that is what the 5D II is meant to do, where the 7D is more action oriented.


I think regardless of the test, you are going to get similar results.





Rick

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Originally Posted by HDNitehawk

But just from using the cameras I have it is very evident to me that in equal situations the 7D has more noise than the 5D II.

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By "equal situations", do you mean equal f-numbers, or equal in the sense John did his experiment (with the larger sensor stopped down)? At the same f-number, the larger sensor of course has a major advantage.

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Originally Posted by HDNitehawk

It might be worth looking at how DXO did their comparison to see if it is legitimate.

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The DXO description of their tests looks good to me, but that does not mean they did not make mistakes.

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Originally Posted by HDNitehawk

am not sure what a fair test would be considering the variables. At some point you are going to have to adjust either ISO or Shutter Speed or your Flash. Perhaps a comparison where you have no flash and equal lighting, and choose the shutter and ISO that you would choose for each camera in that situation.

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The test is fair only if both cameras get the same amount of light. No flash and equal lighting as you suggest would be good, but the shutter speeds *must* be the same.

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Originally Posted by Jon Ruyle

The test is fair only if both cameras get the same amount of light. No flash and equal lighting as you suggest would be good, but the shutter speeds *must* be the same.

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Wouldn't you have to disregard the DOF difference of the two lenses. Pardon my ignorance here I am making this assumption, but to get the proper identical exposure even the aperture would be have to be the same in your scenario. Your subject would look different because of the 1.6x deeper depth of field so while the comparison would have the same framing the general feel of the picture would be different.

Jon, the increased Speedlite power was not to compensate for the sensor differences, but to compensate for the 2.5- and 5-stop aperture decrements. In theory, a decrease in aperture and a corresponding increase in available light, holding shutter speed constant, means the same amount of light hitting the sensor, right? Having said that, I did rely on the E-TTL II flash metering, and there were some exposure differences (within 1/2 stop), and color temp differences due to the balance of flash vs. ambient (tungsten/halogen), which I equalized in the RAW conversion using the ColorChecker as a reference.


Rick, my experience matches yours as far as the 5DII and 7D go - the 7D is just plain noisier, significantly so.


Honestly, I wasn

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Originally Posted by HDNitehawk

but to get the proper identical exposure even the aperture would be have to be the same in your scenario.

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Using the same aperture would defeat the point, because the one with the larger sensor would have a narrower DOF... that's a *different picture*, thus not comparing apples to apples.


What John is trying to do (and what seems to me the only reasonable thing to do) is to compare two different camera/lens combinations taking the *same picture*. So they should have the same aperture and same focal length (thus same DOF and same perspective and angle of view). Obviously the f numbers will be different.


If we want to compare noise, we should use the same shutter speed and similar lighting. If we use a slower shutter speed with one camera, we're giving that camera more light and thus giving it an advantage. If we use a flash and allow the different meters to decide how bright to make the flash, the cameras are getting different amounts of light.


There is no need to think about ISO at all, since it has no effect on photon noise (it can affect read noise, but I think this is outside the scope of the ff vs crop comparison). The only consideration for ISO is that it should be set so that both pictures are exposed reasonably. If we do this, the camera with the larger sensor will have a higher ISO, but will have no inherent advantage or disadvantage because of sensor size.


If you are comparing your 1DIV or 5DII vs the 7D using the same iso, of course the 5DII and 1DIV with their larger sensors will do better.

I agree that FF will do better than APS-C on noise. But the theory seems to suggest a 1.3-stop difference, and my impression is that the 5DII-7D differential is greater than that, which is what I

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Originally Posted by neuroanatomist

n theory, a decrease in aperture and a corresponding increase in available light, holding shutter speed constant, means the same amount of light hitting the sensor, right?

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When you say "decrease in aperture" I think you mean "increase in f number". In your tests, the apertures were the same, as was appropriate (f numbers were different because the focal lengths are different). If the apertures (not f numbers) are the same, effective focal lengths are the same, lighting is the same, and the shutter speeds are the same, each sensor is getting the same amount of light.

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Originally Posted by neuroanatomist

I now just take for granted that the 7D is noisy by comparison.

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That depends on how you do the comparison. At the same ISO, the of course the 7D has far more noise. But if you take the same picture with both cameras, I think the 7D will have less noise.

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Originally Posted by neuroanatomist

Honestly, I wasn't thinking much of noise when I set this up

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I wasn't either when I first looked at it... it wasn't until you said the 7D was noisier that I thought... "wait, something is wrong...." (Not wrong necessarily, but not geared to compare noise.)

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Originally Posted by neuroanatomist

Jon, Rick, how would you suggest I set that up? I'm thinking of shooting the ColorChecker, using the same lens for equal transmittance, but...the 100 L Macro and change distance, or the 70-200/2.8 II and zoom to compensate for crop?). Manual exposure, same aperture for both cameras (since sensor size doesn't affect exposure), and a flat target obviates DoF. What else?

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I think you're making it too complicated. Set your cameras so they take the same picture (as you have done with different lenses and the same aperture). Give them both the same amount of light (ie, same lighting, same shutter speed). Then you have a fair comparison. I would suggest using manual mode under the same lighting and no flash, and setting the ISO so the pictures look similarly bright or so the histograms look similar (ISO does not affect photon noise).


Transmission will be different because the lenses are different, but I don't think that is a biggie, and I don't see a way around it (using the same lens on different cameras with different f/ settings will not give exactly the same transmission percentages either)

I really admire your knowledge and highly inteligent testing setups, it

Yes there is an equivalent, the 1200mm f/5.6 L. But that thing is a beast and costs as much as a small house in the county!


Here Bryan reviews it www.the-digital-picture.com/.../Canon-EF-1200mm-f-5.6-L-USM-Lens-Review.aspx.


Enjoy. Oh, and please wipe off the drool when your done....[:D]


John.

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Originally Posted by Jon Ruyle

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Originally Posted by neuroanatomist

Jon, Rick, how would you suggest I set that up? I'm thinking of shooting the ColorChecker, using the same lens for equal transmittance, but...the 100 L Macro and change distance, or the 70-200/2.8 II and zoom to compensate for crop?). Manual exposure, same aperture for both cameras (since sensor size doesn't affect exposure), and a flat target obviates DoF. What else?

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I think you're making it too complicated. Set your cameras so they take the same picture (as you have done with different lenses and the same aperture). Give them both the same amount of light (ie, same lighting, same shutter speed). Then you have a fair comparison. I would suggest using manual mode under the same lighting and no flash, and setting the ISO so the pictures look similarly bright or so the histograms look similar (ISO does not affect photon noise).


Transmission will be different because the lenses are different, but I don't think that is a biggie, and I don't see a way around it (using the same lens on different cameras with different f/ settings will not give exactly the same transmission percentages eithe

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John


Using the same lens and adjusting distance should work, If you are just checking noise. I think low even light would be the best since you are trying to make noise.


I think Jon's suggestion would work. But how are you going to quantify the noise. And would there be some ratio that one shows more noise than the other, for instance the 7D would have 1.6x the amount of noise of the 5D? Which I am sure will not be the case.


Rick

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Originally Posted by HDNitehawk

Using the same lens and adjusting distance should work, If you are just checking noise. I think low even light would be the best since you are trying to make noise.


I think Jon's suggestion would work. But how are you going to quantify the noise. And would there be some ratio that one shows more noise than the other, for instance the 7D would have 1.6x the amount of noise of the 5D? Which I am sure will not be the case.

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You and John are right- using the same lens and stopping down will work fine. Plus, if you only want to measure noise, it is better to use the same lens (I take back what I said about stopping down changing the transmission percentages: I thought about it some more and I think that using the same lens at different f stops will give very close light transmission rates)


Quantifying noise is tricky. The guys at dpreview tried it and failed, and came to the wrong conclusion that cameras with smaller pixels have more noise. I suspect that this is because they did something like "take a picture of a grey card and compute the standard deviation of the pixel values". The problem with this method is that vignetting will cause increased standard deviation (it is easy to correct for this- but it must be done)

<span>I set up an additional test scene to look more
specifically at noise and dynamic range differences between the 5DII and
7D.<span> For this test, I used the EF
70-200mm f/2.8L IS II, using the zoom to compensate for the FOV difference
between sensor sizes.<span> Since the goal was
to look at ISO noise, I took &lsquo;different pictures&rsquo; in the sense that the DoF was
different because I used the same aperture setting for both bodies &ndash; that
served to keep exposure constant for all of the images.<span> The test setup looked like this:


<span>[img]/cfs-file.ashx/__key/CommunityServer-Components-UserFiles/00-00-00-35-15/5DIIvs7D-Setup.jpg[/img]


<span>
<span>Lighting was from a pair of 150 W-equivalent gooseneck
lamps (room lights were off).<span> Relevant
features within the image frame (shown by the magenta box) of the test setup
included:

• Background: ISO
  12233 chart (an enhanced version meeting the ISO 12233 spec but adding greater
  LW/PH resolution and features for SFR analysis)
• Lower left: X-rite
  ColorChecker Passport
• Lower middle:
  Datacolor SpyderCube
• Lower middle:
  Textured napkin (behind SpyderCube) for highlight detail
• Right side:
  Stouffer 21-step transmission wedge (each step is 0.5 stops)
• Lower right: High
  Resolution Target NIST 1010A &ndash; this is a chrome-on-glass microscope slide used
  for calibration of transmitted light image analysis systems

<span><span>
<span>The last two items were backlit by a fluorescent light
pad.<span>



<span>
<span>The cameras were set to Manual Mode.<span> Two exposure settings were used, and in both cases, exposure was right at the threshold of clipping the highlights:

• 1/60 s,
  f/5.6 for shots with the gooseneck lamps on, Live View manually
  focused on the ISO 12233 chart, WB set to tungsten
• 1/40 s, f/5.6 with the goosenecks off (so
  only the backlit step wedge and microscope slide were illuminated), Live
  View manually focused on the microscope slide, WB set to fluorescent

<span><span>
<span>Shots were taken at increasing full-stop &lsquo;native&rsquo; ISO
settings (avoiding the &lsquo;tweener&rsquo; ISOs).<span> As
ISO was increased, exposure was kept constant by the addition of B+W ND filters
(1-, 2- and 3-stops, stacked as needed for a full 6-stop range compensating for
the range of ISO 100-6400).<span> One thing I
noticed &ndash; the B+W #103 ND filter isn&rsquo;t a full three stops, more like 2.67
stops.


<span><span><span>
<span>The first set of 100% crops shows noise on the
ColorChecker:


<span><span><span><span>[img]/cfs-file.ashx/__key/CommunityServer-Components-UserFiles/00-00-00-35-15/5DIIvs7D-Noise-Composite.jpg[/img]


<span><span><span><span>
<span>Results are pretty much as expected, perhaps
even a little better &ndash; I expected the 7D to perform worse than the predicted
1.3-stop difference due to FF vs. APS-C, but it seems to be just about the
predicted difference, at least by qualitative evaluation.


<span><span><span><span><span>
<span>The second set of 100% crops shows highlight
detail, and also some sharpness differences (ignore the resolution value of 30
lw/ph since the framing of the ISO 12233 chart in this setup is not intended
for resolution testing):


<span><span><span><span><span><span>[img]/cfs-file.ashx/__key/CommunityServer-Components-UserFiles/00-00-00-35-15/5DIIvs7D-Highlight-Composite.jpg[/img]


<span><span><span><span><span><span>
<span>Highlights are well preserved throughout.<span> I won&rsquo;t post them, but the series with the
goosenecks off and only the backlit step wedge shows that the dynamic range is
similar between the two cameras &ndash; about 9 stops on the step wedge, becoming a
bit less at the upper end of the ISO range.<span>



<span><span><span><span><span><span><span><span>On e interesting &lsquo;feature&rsquo; is the diagonal RGB
color banding that shows up on the 30 lw/ph lines in the 7D images, but not the
5DII images.<span> It appears to be partly a RAW
conversion artifact &ndash; the image below is a screenshot of the RAW file and the
DPP-converted JPG opened side by side in Preview (the Mac OS X viewer app), and
the banding is not as obvious in the RAW file (left), although it's present if you look carefully (as lighter diagonal bands, without the color artifact), especially if you rapidly scroll the image up and down on the screen.


[img]/cfs-file.ashx/__key/CommunityServer-Components-UserFiles/00-00-00-35-15/5DIIvs7D-ColorBanding.jpg[/img]


<span><span><span><span><span><span><span><span> As usual, comments, feedback, and re-interpretations are welcome!


<span><span><span><span><span><span><span><span>--John

Nice detail work again John. I am seeing no suprises here.


+1 for the 5D II in this test


From personal use this is my perception: the dynamic range would be similar in the two bodies (7D and 5D II). The 1D IV seems to have an edge on the other two in this regard.

To my eye, the 5D is just about a stop better. Comparing the 5DII image to the 7D one level up, sometimes one side looks nosier to me, sometimes the other. I

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Originally Posted by Jon Ruyle

Of course, the test isn't exactly even: comparing 100% crops is a little unfair to the 5DII because it has more pixels. This is a difference of just less than 1/4 stop (about 0.23 stops). So if you think the tests reveal a 1 1/3 stop difference, there is really more than a 1 1/2 stop difference.

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I am not sure you could do an even test. One that John did a while back we compared a 5D shot croped to match the 7D framing to show the 7D could have IQ as good as the 5D II when using your longest telephot lens. In that test the 7D in some respects matched or exceded the 5D and in a few aspects it trailed. You could say this test wasn't fair as well for the same reason, the 7D's pixel count over the croped area was higher than the 5D II's.


I think for an overall comparison you would have to try several diffrent senarios. So far all of the senarios I have seen the 7D trailed the 5D II in noise. I think every senario you would try would favor slightly one body or the other.


Here is another thought, that I do not know the answer on. Could this be a lens vs light thing instead of a sensor vs sensor issue?

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Originally Posted by HDNitehawk

I am not sure you could do an even test.

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I think you can come close. John's test seems pretty good to me, provided you normalize for pixel size.

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Originally Posted by HDNitehawk

<span>One that John did a while back we compared a 5D shot croped to match the 7D framing [...]You could say this test wasn't fair as well for the same reason, the 7D's pixel count over the croped area was higher than the 5D II's.

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Agreed.

Thanks for this test, John!

Great tests John. I bet you put a ton of time into that and I thank you.


Jayson

Like the others, I very much appreciate the time and effort you

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Originally Posted by Kayaker72

it also seems to be decreasing the sharpness of the 7D images significantly more than the 5DII. Anyone have an idea as to why?

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That is no surprise: the 7D pixels are much smaller, so flaws appear magnified.

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Originally Posted by Jon Ruyle

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Originally Posted by Kayaker72

it also seems to be decreasing the sharpness of the 7D images significantly more than the 5DII. Anyone have an idea as to why?

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That is no surprise: the 7D pixels are much smaller, so flaws appear magnified.

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This may be true, but I will givemy theoryas well:


The 70-200mm will produce different results at diffrentpoints. I find the 200mm end to be sharper than the 70mm end. So in the comparison that John made it was a good comparison for noise. But in this test I think it would have been biased for sharpness moretowards the 5D II more so because of the different lengths used. If you ran other scenarios where you used the same lens at different distances, I think the test would be biased to the 7D because of its greater DOF it would appear to be sharper. (whether it actually would be or not is a different story)

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Originally Posted by HDNitehawk

I find the 200mm end to be sharper than the 70mm end.

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That, too. Definitely.

Thanks for the feedback! FWIW, the approximate focal lengths on the zoom were 85mm for the 7D and 135mm for the 5DII.

I added some larger composites (1600 pixels wide) toFlick<span style="color:#ff00ff;"]r photo tests page. A new composite looks at color - I was surprised to see the amount of desaturation in the red channel with increasing ISO (click image for full size).


http://farm3.static.flickr.com/2673/...96fc8c70_b.jpg

If you're doing a colour test, there are far too many variables here and also I'd question some of the choices (e.g. tungsten lamps and AC ones at that shot at 1/60... unless that's only what you want to know about).


For example you should have used the exact same area of the image circle of the lens at one focal length when doing the test. Although we don't always notice it, colours change at different points on the image circle, focal lengths, apertures, etc. Since this is not a resolution/noise test, you can always keep both cameras at the same distance, same focal length+f-number on the zoom and then compare the colours.


And the use of a preset WB is questionable, because it's likely to be different between the cameras. If you really want to know how the two sensors behave under such light, you should have no WB adjustments applied.


Also I'm not sure whether the ND filter use is a good idea (stacking aside). Sensors have different response curves and the transmission curves of the filters can make things favourable for one camera and bad for the other. So with a different brand of ND filters, you most likely will see a different outcome. Also the filters will add their own flare (reducing the contrast) and color casts (hopefully evenly, but unlikely... another reason to use the same area of the image circle) but at least it will be constant for both setups.


Constructing the test the way I'm suggesting could be perceived as being "too artificial" to be relevant for every day use but, then again, so is this. I see highly controlled test setups as a necessary evil to understand the most fundamental/constant differences, whether or not they will be obvious in general usage.


Good luck! :)


GTW

Interesting John.


I have noticed that in certain situations the 5D II can have a problem oversaturating in red. For most types of pictures red isn

Thanks for the feedback, GTW. It wasn't intended as a color test, but the desaturation just 'jumped out' at me as I looked at the images. The desaturation with increasing ISO does not seem to be different between the two bodies, so the concerns about using the same area of the image circle and different preset WB are obviated when just looking at increasing ISO on one body.


Incidentally, though, you're quite correct about the WB being different between the cameras - although DPP does not show the actual color temperature of the WB settings, DxO does. For tungsten WB, the 5DII uses 3455 K / +4 tint, whereas the 7D tungsten WB is 2527 K / -21 tint. Likewise, the fluorescent WB settings are 4292 K / +18 for the 5DII and 3990 / -14 for the 7D. Still, I think a preset might be the best option - the presets are set such that a light source of a given temperature (e.g. 3200 K for tungsten, and presumably Canon uses the same source temperature for all their cameras) render light from neutral gray object as neutral gray. That should compensate for differences between the sensors (Bayer masks, actually) in terms of their color sensitivities. As a practical note, how can one, "have no WB adjustments applied?" There will always be a color temperature associated with the image - even though it's a metadata setting, it's always used to display the image. Presumably, you mean setting the color temperature to the same value (e.g. 3200 K for tungsten) for both cameras - but in that case, neutral wouldn't be neutral anymore (which is the whole reason tools like the ColorChecker are available, right?).


I did give some thought to the use of ND filters. The reason for that was to keep exposure (aperture and shutter speed) constant across all the ISO settings, since I was primarily looking at noise. I agree that with a different brand of filters, the results would be different. With the B+W filters, at least, they publish the transmission curves - for the 3 filters that I used #101, #102, and #103), they are reasonably flat across the visible spectrum. If anything, transmission in the red/far red part of the spectrum is slightly higher (an effect that gets more pronounced with the higher density filters) - so in theory, the addition of the ND filters should slightly enhance saturation in the red channel (i.e. the desaturation might be worse than seen in this test). Still, it's a variable I'd like to control for, so I will probably reshoot just the ColorChecker with one camera, varying the shutter speed with ISO instead of using filters to control exposure.

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Originally Posted by genotypewriter

I see highly controlled test setups as a necessary evil to understand the most fundamental/constant differences, whether or not they will be obvious in general usage.

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I agree - it's important to keep the perspective that contrived tests only show a small part of the truth. I like Bob Atkins' analogy of representing the quality of a lens with a single number, e.g. an MTF50 averaged across the frame, which he likens todescribing the Mona Lisa by it's average color. Still, in this case, cranking up the ISO of an image to boost sensitivity (which is in keeping with the ETTR philosophy) might have the unintented consequence of negatively impacting the color palatte of the image - and that's a real-world consequence.