35mm L lenses on APS-C sensor cameras?

Hi!

I've been searching around the net to find out what happens if I attach a Canon L series lenses to a APS-C sized sensor cameras. I found several sites with images and lots of information, but did not get a clear answer. I understand the framing difference, but I can’t figure out the thing with numbers.
If I attach for example Canon EF 70-200mm f/4.0 L IS USM lens to my Canon 600D, do I get at maximum zoom the same results as wit Canon EF-S 18-200mm f/3.5-5.6 IS Lens? Or I get with EF 70-200 L lens 200x1.6=320mm which is more zoom than EF-S 18-200 lens?

Thanks in advance!

If you attach a 70-200mm lens to a camera with an APS-C sized sensor, it will have a Full Frame equiv. focal range of 112-320mm. If you attach a 35mm lens to a camera with an APS-C sized sensor, it will have an equiv. focal length of 56mm.

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Originally Posted by Sean Setters

If you attach a 70-200mm lens to a camera with an APS-C sized sensor, it will have a Full Frame equiv. focal range of 112-320mm. If you attach a 35mm lens to a camera with an APS-C sized sensor, it will have an equiv. focal length of 56mm.

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And if you attach an 18-200 to your camera it will have a Full Frame equiv. focal range of 28.8-320mm. The crop factor is 1.6 regardless of whether it is an EF or EF-S lens.

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Originally Posted by Rubar

If I attach for example Canon EF 70-200mm f/4.0 L IS USM lens to my Canon 600D, do I get at maximum zoom the same results as wit Canon EF-S 18-200mm f/3.5-5.6 IS Lens? Or I get with EF 70-200 L lens 200x1.6=320mm which is more zoom than EF-S 18-200 lens?

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Focal length is an intrinsic property of the lens, and is a measure of the distance between the rear nodal point of the infinity-focused lens and the focal plane (sensor). Sensor size (APS-C vs. FF) has nothing to do with it and no effect on focal length. The numbers printed on the barrel of the lens are not somehow 'adjusted' for the sensor size, at least with dSLR lenses (some point-and-shoot cameras do have the FF equivalent focal lengths printed on them). What a smaller sensor like APS-C does is only capture a smaller portion of the image circle projected by an EF lens, and EF-S lenses are designed with a smaller image circle (which is why they don't work on FF cameras) to reduce size, weight, and cost.

So, in theory for your example of the EF 70-200mm L lens vs. the EF-S 18-200mm, if you use them both on the same camera, 200mm will give you the same field of view. In practice, there is a difference in this case - the 18-200mm lens doesn't really deliver 200mm at the long end; I tested one a while back, and it was more like ~160mm at the long end when compared to the same shot taken with the 70-200mm f/2.8L IS II.

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Originally Posted by neuroanatomist

I tested one a while back, and it was more like ~160mm at the long end when compared to the same shot taken with the 70-200mm f/2.8L IS II.

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Interesting:eek:

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Originally Posted by Rubar

Hi!


If I attach for example Canon EF 70-200mm f/4.0 L IS USM lens to my Canon 600D, do I get at maximum zoom the same results as wit Canon EF-S 18-200mm f/3.5-5.6 IS Lens? Or I get with EF 70-200 L lens 200x1.6=320mm which is more zoom than EF-S 18-200 lens?

Thanks in advance!

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No, they will be the same. All of the 1.6 hype is talking about camera bodies and sensors. Unless you plan on buying a full frame camera all of the Crop to FF comparisons are really useless information for you.

There is one thing you will get out of the 70-200mm L. Better IQ....

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Originally Posted by neuroanatomist

. In practice, there is a difference in this case - the 18-200mm lens doesn't really deliver 200mm at the long end; I tested one a while back, and it was more like ~160mm at the long end when compared to the same shot taken with the 70-200mm f/2.8L IS II.

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That one is odd. I think I would go back and check the testing methods. Canon could owe allot of people money for false advertising, I wonder what 40mm would be worth in a class action lawsuit

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Originally Posted by neuroanatomist

I tested one a while back, and it was more like ~160mm at the long end when compared to the same shot taken with the 70-200mm f/2.8L IS II.

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I'm curious to the testing method as well. Stars are the only target I can think of that one could use as an infinite-distance source. I've used systems in the lab that are functionally 25% less magnification than their quoted values at "real" distances but if we test them with a collimated source they generally are right where the manufacturer says they are. Though I would not be shocked if these lenses (or at least the one tested) did not turn out to perform as spec'd. That happens all the time in the lab as well...

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Originally Posted by Rubar

I found several sites with images and lots of information, but did not get a clear answer.

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It may help to compare camera format with digital zoom. Let's say you start with a 5D2 and 200mm lens, and want to compare various methods of "zooming in":

1. Optical zoom: switch to a 320mm lens.
2. Digital zoom: use the 200mm lens, but crop the 21 MP image down to 8MP.
3. Digital zoom: use the 200mm lens on a Canon 30D (8 MP).
4. Digital zoom with high resolution: use the 200mm lens on a Canon 60D (18MP).

Options 2 and 3 yield nearly identical resolution, even though they are different cameras, because they have the same pixel size, pixel count, and focal length. But option 4 is going to have superior resolution as long as diminishing returns don't cancel out the benefit of smaller pixels.

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Originally Posted by HDNitehawk

That one is odd. I think I would go back and check the testing methods. Canon could owe allot of people money for false advertising, I wonder what 40mm would be worth in a class action lawsuit

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The 18-200mm *is* 200mm at infinity. I'm sure that Neuro's test was for a much closer focus distance. Focal length can vary with normal manufacturing tolerances, and +/- 5% wouldn't surprise me, but 20% certainly would.

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Originally Posted by HDNitehawk

That one is odd. I think I would go back and check the testing methods. Canon could owe allot of people money for false advertising, I wonder what 40mm would be worth in a class action lawsuit

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My testing method was to focus on an object at a reasonable distance (50 feet or so) and take a picture with the 18-200mm at 200mm and the 70-200mm L at 200mm, then overlap them in Photoshop and estimate the relative cropping. It was significant. Bryan notes the same phenomenon in his review of the 18-200mm, and the pics of the starfish seem no different at 170mm vs. 200mm.

It could just be really bad focus breathing, such that anything even a little less than infinity focus results in a much shorter apparent focal length. Most people who buy a 100mm L Macro don't know they're really buying a zoom lens :p, and at 1:1 magnification the effective focal length is only 80mm. But in the case of the 18-200mm, I wasn't anywhere near a 'macro' distance.

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Originally Posted by neuroanatomist

It was significant. Bryan notes the same phenomenon in his review of the 18-200mm, and the pics of the starfish seem no different at 170mm vs. 200mm.

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Wow...this really muddies the answer to Rubar's original question. If you go to Canon's website it says that this lens is the FF equivalent to 29mm-320mm. If what you and Bryan found is true, which I do not doubt what you found, this would really be blatant false advertising. But I guess 18-200mm just sounds and sells better than say a 18-170mm

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Originally Posted by Daniel Browning

The 18-200mm *is* 200mm at infinity. I'm sure that Neuro's test was for a much closer focus distance. Focal length can vary with normal manufacturing tolerances, and +/- 5% wouldn't surprise me, but 20% certainly would.

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Daniel, I think we are confusing manufacturing tolerances with marketing tolerances. I think within 30% accuracy would be the norm for Canon's marketing accuracy. They just tweaked the numbers so they got a nice even 200

Maybe Canon measures focal length in 'man-millimeters'?

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Originally Posted by neuroanatomist

Maybe Canon measures focal length in 'man-millimeters'?

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Can you shoot some stars tonight with this lens and a 70-200 (and a 200 prime if you have one) all at max focal length? I suspect the problem Bryan saw was in the combination of zoom and focus. Up close the optical changes required to focus the light may have masked the change in focal length. And, unfortunately, Canon's definition of "close" might be half a mile.

Remember, the effective focal length of a lens actually only applies to paraxial (near the optical axis) rays of an infinite source. That's not to say that's how a lens will behave at finite conjugates nor anywhere but on the optical center (just read your profile so I'm sure you're well aware of this fact - microscopy is littered with marketing half-truths - same as many diagnostics fields).

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Originally Posted by ChadS

Can you shoot some stars tonight with this lens and a 70-200 (and a 200 prime if you have one) all at max focal length?

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Sorry...I don't own an EF-S 18-200mm, I just tried one out in a store out of curiosity (I brought my 7D and 70-200mm f/2.8L IS II with me).

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Originally Posted by neuroanatomist

My testing method was to focus on an object at a reasonable distance (50 feet or so) and take a picture with the 18-200mm at 200mm and the 70-200mm L at 200mm, then overlap them in Photoshop and estimate the relative cropping. It was significant. Bryan notes the same phenomenon in his review of the 18-200mm, and the pics of the starfish seem no different at 170mm vs. 200mm.

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It's probably just two additional factors: 1) the difference between x feet and infinity, and 2) the difference in the center of perspective. If you setup a tripod and just change lenses, then you may not realize that you're also changing the location where light enters the lens-- the entrance pupil. For example, imagine you have a 50mm lens that is 5 feet long, but through the magic of optics gives you an angle of view that is truly 50mm. Then you have a 50mm lens that is only 5 inches long. If you setup the tripod and compare them by just swapping lenses, the 5-foot-long 50mm lens will give a different field of view. But if you instead align them based on the center of perspective, which is the entrance pupil (or virtual image of the lens' aperture), for both lenses, then compare them, they would yield the exact same field of view (and angle of view).

Hi again!
To be honest, I did not expect so many replies. Thank you all for your input. As I see there are many different opinions and excitement, but still no clear answer. At least I still don’t get it. I shoot different objects with Canon EOS 600D at about 100-300 meters (328-980 feet). With EF-S 18-200mm f/3.5-5.6 IS lens I get quite satisfying results for my purpose. Only thing I’m missing is a little extra zoom. While planning to get a new lens I consider getting a higher quality one.

I think to give a clear answer to my question a real-life test is needed. Unfortunately I don’t have an opportunity to borrow such lenses from anyone and our stores are not going to allow me to do this either. Maybe someone has those lenses or can borrow them and test them in a distance.

So the test would have a camera with APS-C sized camera. For this test I believe there won’t be a big difference which model it is. Take 3 photos at a distance of approximately 300 meters (980 feet), but definitely all there at the same distance with the same camera:
1) one photo with EF-S 18-200mm f/3.5-5.6 IS Lens (or similar EF-S lens) at 200mm
2) one photo with EF 70-200mm f/4.0 L IS USM Lens (or similar EF lens) at 200mm
3) and one with EF 200mm f/2.8 L II USM Lens (or similar EF lens) which has fixed 200mm
4) unfortunately there is no EF-S lens with fixed 200mm, that I would know of.

Then if those photos are uploaded to this forum, we all can compare them and see the difference. Of course if such a test will take place then it could be expanded to more different focal lengths, object distances and different lenses. What you think? Would it make few things clear?

Anxiously waiting for results, new thoughts and ideas

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Originally Posted by Rubar

Hi again!


So the test would have a camera with APS-C sized camera. For this test I believe there won’t be a big difference which model it is. Take 3 photos at a distance of approximately 300 meters (980 feet), but definitely all there at the same distance with the same camera:
1) one photo with EF-S 18-200mm f/3.5-5.6 IS Lens (or similar EF-S lens) at 200mm
2) one photo with EF 70-200mm f/4.0 L IS USM Lens (or similar EF lens) at 200mm
3) and one with EF 200mm f/2.8 L II USM Lens (or similar EF lens) which has fixed 200mm
4) unfortunately there is no EF-S lens with fixed 200mm, that I would know of.

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If someone did this test, I suspect the results would be as follows. Each of the 3 shots would have a similar (or per Neuro's testing, maybe not so similar) framing of the subject at 200mm. Take 3 different lenses on the same camera at 200mm, and you will get 3 (at least) slightly different framings because of manufacturing variations. The focal length stamped on the camera is an approximation. But the variation shouldn't be major. And if you are looking for more reach, you need a lens with a longer focal length. It's not easy to capture subjects 300 meters away unless the subject is quite large.

Neither the 70-200 or the 200 prime will get you significantly more reach. For that you need a 70-300, 100-400 or a super tele prime lens.

For what it's worth, the hypothetical test would also yield quality differences....at 200mm, I suspect the 18-200 would have the "worst" IQ of the bunch, with the 70-200 and the 200 prime duking it out for the win, with the prime edging the zoom. Then, the f-stop selected for the test plays a role too -- not in how the photo is framed, but in terms of depth of field. The 18-200 at 200mm will have a max aperture of f5.6 (more depth of field); the zoom at f4 (less depth of field); and the prime at f/2.8 (even less depth of field). Depending on the focal point of the shot, the results from the three lenses could look quite different due the aperture setting. If all shots in the test were taken at f5.6 (the least common f-stop), the depth of field should be the essentially same in all three shots -- and I would suspect the prime would be an even easier pick for the IQ winner in that case.

I agree with thekingb, if what you want is more reach get a longer lens than 200mm. If you really get a tighter framing from the L lenses, it isn't going to be enough that you really notice in real world situations.

You are going to have a hard time finding someone that has all three of those lenses. Most people with those two L lenses in their kit have no use for the 18-200mm, unless they just upgraded.

I'll have a go at a clear answer. If you put any lens labeled 200mm on your camera, and set it to 200mm if it's a zoom lens, you'll get essentially the same picture. Doesn't matter if it's EF-S, EF, or L.

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Originally Posted by neuroanatomist

I'll have a go at a clear answer.

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Admirable concision!

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Originally Posted by neuroanatomist

If you put any lens labeled 200mm on your camera, and set it to 200mm if it's a zoom lens, you'll get essentially the same picture. Doesn't matter if it's EF-S, EF, or L.

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If this is true, then at least some numbers must be incorrect (converted). As I said before, I’ve been surfing around a lot on this subject and found some images. For example at Wikipedia they have this image:
http://upload.wikimedia.org/wikipedi...CropFactor.png
From this illustration I can see, that EF lens which is made for full frame 35mm cameras gives on APS-C sensor cameras more zoom at the same focal length. Correct?

Another great illustration at BobAtkins:
http://www.bobatkins.com/photography...ensor_view.jpg

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To get the same field of view as a 28mm lens on the full frame camera, you'd need a shorter focal length lens when used with the APS-C crop sensor. That's illustrated by the green lines in the image above. In the case of EOS DSLRs, the focal length would need to be 17.5mm.

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These both images and explanations make sense to me, but I'm really confused by neuroanatomist’s statement. If EF-S and EF lenses give the same results at the same focal lengths, then it means that illustrations above are incorrect. But they look quite logical to me. Still, if both images and neuroanatomist are true, then it means numbers on either EF-S or EF lenses are incorrect. With this theory it means EF-S focal length at 200mm is actually less to project the same image on a smaller sensor. Which means that EF-S lens at 200 mm is actually 200/1,6=125mm and Canon writes on a camera not true focal length, but equivalent of 35mm. Could this be true?

This is getting too complicated.
Neuro's quote above is, "If you put any lens labeled 200mm on your camera," please note he said your camera, an APS-C not a FF. And he is right any 200mm lens that fits will show the same image on your camera.

If you put those lenses on a FF the image will be different. The 1.6 crop factor hold for APS-C basically means on crop bodies or smaller sensor cameras like your 600D the image you obtain with a 200mm lens is the equivalent to an image of 200mm x 1.6 = 320mm lens on a FF or 35mm camera.

Neuro's response agrees with your diagrams, in the quote you highlighted he was only referring to your camera, not other formats.:)

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Originally Posted by neuroanatomist

I'll have a go at a clear answer. If you put any lens labeled 200mm on your camera, and set it to 200mm if it's a zoom lens, you'll get essentially the same picture. Doesn't matter if it's EF-S, EF, or L.

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Hopefully I do not add to the confusion. However, Neuro is correct in his statement. The lens passes light through it and projects it in a round circle at the focal plan. The FF sensor then crops (only looks at) a rectagular sample of that projected image equivilant to the sensor size. If that FF sensor is replaced with a smaller "Crop sensor", then that round circle of light projected onto the sensor only sees the portion of the light that hits it, and therefore an even smaller portion of the projected area of light is recorded (thus the 1.6X crop factor).

What I thought he was saying is at the focal plan the lens produces the same image, and then whatever sensor you put in the focal plan will then crop that circle of light down to the size of the sensor. The problem with this comes with the EF-S lenses... with these the circle of light that is projected onto the focal plan is smaller than the size of the FF sensor so if you could put a EF-S lens on a FF camera, then the corners would be blackened.

If I have anything wrong here, please correct me; but that is my understanding.

Rubar

Neuro's assessment is correct. Your post on the charts makes me wonder if you think that EF lenses are "Full Frame" lenses. While EF-S lenses are made for crop bodies. EF lenses are made for all bodies. The diagrams you show are referring to the difference in sensors. EF lenses are not full frame lens, nor are they crop lenses they are just lenses. If you want more reach, you should be looking at longer lenses.

I will disagree with conropl on what you would see if you put on the EF-S lens on your full frame. I will speculate a bit. You would most likely just see black after you broke your mirror. :p Or maybe a error message on your lcd telling you the camera no longer functions.

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Originally Posted by HDNitehawk

I will disagree with conropl on what you would see if you put on the EF-S lens on your full frame. I will speculate a bit. You would most likely just see black after you broke your mirror. :p Or maybe a error message on your lcd telling you the camera no longer functions.

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That is why I said "if" you could put an EF-S on a FF camera.:p

:p I noticed you qualified it with "if you could". You know I never tried to mount one on my FF bodies, fear always kept me from it. But I see no reason why it wouldn't mount right up so a person could break their camera.

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Originally Posted by Rubar

Hi again!
To be honest, I did not expect so many replies. Thank you all for your input. As I see there are many different opinions and excitement, but still no clear answer. At least I still don’t get it. I shoot different objects with Canon EOS 600D at about 100-300 meters (328-980 feet). With EF-S 18-200mm f/3.5-5.6 IS lens I get quite satisfying results for my purpose. Only thing I’m missing is a little extra zoom. While planning to get a new lens I consider getting a higher quality one.

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By extra zoom, you mean longer focal length. That means you need a lens longer than your current max of 200mm. An EF 70-200mm L lens will give you better quality, but no more 'reach'. So, consider lenses like the 70-300mm f/4-5.6L IS, or the 100-400mm, the 300mm f/4L IS, or the 400mm f/5.6L. All of those will give you better quality, and a longer focal length (some more than others).

Bottom line, for you right now, only the number matters. You can get any lens, EF-S, EF, or L, but if you want more zoom than your current 18-200mm lens, you need a lens longer than 200mm. All of the diagrams you posted and the discussions that you referred to will only apply to you if/when you decide to get a full frame camera like a 5DII. At that point, a 200mm lens on that full frame camera will give you the same field of view as a 125mm on your current camera, so if you go FF, you may need longer lenses, too. But for now, don't worry about any of that.

I think I’m starting to get it. Thanks to all of you!
Just to clarify, please tell me am I right or wrong stating:
With the same 200mm L lens I get on 35mm (full frame) camera wider frame and on APS-C will get a more close-up (more zoom).

@Rubar Yes that's basically it. You could also say "the crop camera will create an image that's a cutout of the full frame image." If I mount a lens in one spot and shoot with a full frame camera I'll get one image. With a crop sensor I'll get a different image. However, if I were to print the full sensor image I could make the same picture as the crop camera shot simply by cutting all four sides of the image the appropriate amount.

That's slightly different than zoom but for your purposes it's a close enough explanation.

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Originally Posted by Rubar

I think I’m starting to get it. Thanks to all of you!
Just to clarify, please tell me am I right or wrong stating:
With the same 200mm L lens I get on 35mm (full frame) camera wider frame and on APS-C will get a more close-up (more zoom).

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That works.

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Originally Posted by ChadS

You could also say "the crop camera will create an image that's a cutout of the full frame image."

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I think Chad's phrasing is more accurate. You're not getting any more real magnification with the crop sensor, just cropping away the outer part of the image circle projected by the lens. Here's a visual illustration of that:

http://upload.wikimedia.org/wikipedi...rop_Factor.JPG

The circle is what the lens 'sees', the red rectangle is the image captured by a FF sensor, the blue rectangle is the image captured by an APS-C sensor, all from the same lens.

However, depending on the sensor you might get more apparent magnification. For example, if you use that 200mm lens on a 5DII and crop it to the frame you'd get with APS-C, you have an 8 MP image. So if you used a old 20D (an 8 MP camera) instead of the 5DII, you'd get the same picture as the cropped 5DII image. But, if you use a 600D with an 18 MP sensor, that mountain in the blue rectangle would cover a lot more pixels of the 600D sensor than the 5DII sensor, so if you viewed both side-by-side on the computer monitor at 100% size, the mountain would be 'bigger' when shot with the 600D.