View Full Version : 7d Review- when?
Bunch of reviews starting to pop up. When is the official Digital Picture review coming? can't wait to read it...
Then again, one more glowing review may finally push me over the edge into springing for it. So take your time...
bouwy
11-09-2009, 03:57 PM
I already ordered one (body only), should be here late November. Dpreview gave it the thumps up and seen 3 more reviews saying that the unit is very good. Hope that Canon fixed up the latest bugs on my unit. I wonder if I have to put the (new) enclosed Solution Disk on my computer, or that I can use the one of my EOS 450D, which is already is on my Computer.
Bryan Carnathan
11-10-2009, 10:35 AM
GBC - Hopefully this week or next depending on how my schedule goes. Stay tuned!
musickna
11-11-2009, 02:36 PM
That's good to read, I look forward to it too.
I have already ordered a 7D despite already having the excellent 5D II. I was loathe to get rid of my excellent Canon 17-55mm f/2.8 EF-S or my much-used 10-22mm EF-S wide angle zoom, and with the 7D I believe I will have a camera that will get the best out of these lenses.
bouwy
11-11-2009, 03:00 PM
Look forward to your 7D review.
Sean Setters
11-12-2009, 03:04 PM
DPreview had quite painted quite a glowing picture of the 7D in its review ("http://www.dpreview.com/reviews/canoneos7d/page30.asp). However, this person ("http://darwinwiggett.wordpress.com/2009/11/11/the-canon-7d/) seems to be on the other side of the fence when it comes to the 7D's picture quality.
DPreview had quite painted quite a glowing picture of the 7D in its review ("http://www.dpreview.com/reviews/canoneos7d/page30.asp). However, this person ("http://darwinwiggett.wordpress.com/2009/11/11/the-canon-7d/) seems to be on the other side of the fence when it comes to the 7D's picture quality.
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Sean, interesting find. Thanks.
To quote a friend of mine, "things that make you say, hmm."
Sean Setters
11-12-2009, 05:37 PM
To quote a friend of mine, "things that make you say, hmm."
Yeah, that's exactly what I said. I've had the 7D on my want list since it came out. But that's a rather frightening review. Of course you could make the case that their post processing wasn't right, or else they had in-camera sharpening set to 0 while the others were set higher. But without good evidence tonegate their claims, their review creates some worry in the mind of a potential buyer like myself.
But how could every other review miss such glaring image quality issues?
bouwy
11-12-2009, 07:51 PM
Oh Boy Oh Boy.
I'm picking my 7D up next Monday inclusive an extra battery and the Battery grip. Have paid an non refundable deposit. I'm hoping that all the reviews I have read claiming that the 7D is a real winner are true.
After reading all the above comments I feel like saying "hmm".
Are any 7D owners unhappy with the sharpness of their unit and if so where do they base this on.
Matthew Gilley
11-12-2009, 09:12 PM
I think that Darwin review is biased. They tested at f8, f11 and f13 for the comparisons, below the DLA ("http://www.the-digital-picture.com/Reviews/ISO-12233-Sample-Crops.aspx?Lens=458&Camera=673&Sample=0&FLI=0&API= 2&LensComp=458&CameraComp=673&SampleComp=0&FLIComp =0&APIComp=6) ("http://www.the-digital-picture.com/Reviews/ISO-12233-Sample-Crops.aspx?Lens=458&Camera=673&Sample=0&FLIComp=0& APIComp=6&LensComp=458&CameraComp=673&SampleComp=0 &FLI=0&API=2)for the 7d (f6.8). Bryan's review draft mentions the camera is less sharp than other cameras but is very positive overall.
I think that Darwin review is biased. They tested at f8, f11 and f13 for the comparisons, below the DLA ("http://www.the-digital-picture.com/Reviews/ISO-12233-Sample-Crops.aspx?Lens=458&Camera=673&Sample=0&FLI=0&API= 2&LensComp=458&CameraComp=673&SampleComp=0&FLIComp =0&APIComp=6) ("http://www.the-digital-picture.com/Reviews/ISO-12233-Sample-Crops.aspx?Lens=458&Camera=673&Sample=0&FLIComp=0& APIComp=6&LensComp=458&CameraComp=673&SampleComp=0 &FLI=0&API=2)for the 7d (f6.8).
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All reviews have some bias in them, of course. Read Ken Rockwell's reviews, for example.
Can't the 7D be tested at these apertures? If it's not sharp at these apertures, based on the DLA, shouldn't that be a concern for anyone shelling out $1700 for the 7D?
Jon Ruyle
11-13-2009, 04:22 PM
I think that Darwin review is biased. They tested at f8, f11 and f13 for the comparisons, below the DLA ("http://www.the-digital-picture.com/Reviews/ISO-12233-Sample-Crops.aspx?Lens=458&Camera=673&Sample=0&FLI=0&API= 2&LensComp=458&CameraComp=673&SampleComp=0&FLIComp =0&APIComp=6) ("http://www.the-digital-picture.com/Reviews/ISO-12233-Sample-Crops.aspx?Lens=458&Camera=673&Sample=0&FLIComp=0& APIComp=6&LensComp=458&CameraComp=673&SampleComp=0 &FLI=0&API=2)for the 7d (f6.8).
That's a good point. On the other hand, looking at Bryan's iso12233 crop chart of the 200 f/2 with the 7D ("http://www.the-digital-picture.com/Reviews/ISO-12233-Sample-Crops.aspx?Lens=458&Camera=673&Sample=0&FLIComp=0& APIComp=0&LensComp=458&CameraComp=453&SampleComp=0 &FLI=0&API=0), the 7D looks soft, even with the lens wide open (compare to 1DIII). At first I thought this was just because the pixel density was high enough to reveal weakness in the lens itself. But maybe it is the camera.
All reviews have some bias in them, of course. Read Ken Rockwell's reviews, for example.
Gee, Ken Rockwell biased? Nah... [;)]
I've got the 7d and the 17-55 lens. The pictures originally came out ultra soft but that was because I had been only shooting in stupidly low light. When I shot on a nice day, not too much sun, some cloud coverage, I got tack sharp images handheld, even with my aperture wide open at 2.8! Hope this helps?
Jon Ruyle
11-14-2009, 01:10 AM
Sure, thanks, Jlau. I usually don't put much weight in the odd review that says a camera has soft images, because usually they just did something wrong. But these guys sounded thorough. Nice to hear a report to the contrary.
Daniel Browning
11-14-2009, 11:57 PM
However, this person ("http://darwinwiggett.wordpress.com/2009/11/11/the-canon-7d/) seems to be on the other side of the fence when it comes to the 7D's picture quality.
Sensor resolution is affected by only two things:
Optical Low Pass Filter (OLPF, or anti-alias filter)
Megapixels.
Everything else is processing. If the 7D truly is softer (I have yet to see for myself), it can only be for one reason: Canon improved the OLPF. The 50D OLPF was too weak, and allowed a lot of aliasing artifacts. Many photographers love aliasing artifacts (they call it "sharpness"), and even advocate that the filter be removed. Personally, I think the 50D OLPF was far too weak and I prefer the 20D-style softening.
Jon Ruyle
11-15-2009, 04:01 AM
The 50D OLPF was too weak, and allowed a lot of aliasing artifacts.
Apparently I don't understand. I thought the 50D has a weak olpf because it has a gapless sensor, and thus no aliasing artifacts except those caused by the bayer filter (far less severe than gap aliasing, I would have thought). Am I wrong?
Daniel Browning
11-15-2009, 04:57 AM
Microlenses do reduce aliasing, but a Siemens Star comparison of the 20D and 50D still shows far more aliasing in the 50D (i.e. relative to Nyquist or pixel pitch, not relative to absolute spatial frequency). There is quite a bit of luma (non-Bayer) aliasing in addition to the chroma aliasing (which could be said to be caused by the Bayer filter).
Jon Ruyle
11-15-2009, 11:44 AM
There is quite a bit of luma (non-Bayer) aliasing in addition to the chroma aliasing
Okay. I don't understand how that can be, but then that isn't surprising. I don't understand signal processing at all.
And here is another thing I don't understand, come to think of it: one can do a low pass filter in post processing, so why does one need an optical one?
Daniel Browning
11-15-2009, 07:39 PM
I don't understand signal processing at all.
Wikipedia has a pretty good article on it. ("http://en.wikipedia.org/wiki/Nyquist-Shannon_sampling_theorem) The difference between a sensor with poor optical fill factor (no microlenses) and excellent optical fill factor (gapless microlenses) is like the difference between point sampling and box sampling. A point filter causes more aliasing than a box filter, but the box filter still has quite a bit of aliasing.
One way to look at it is from the point of view of MTF. In order to suppress aliasing, the MTF at the Nyquist frequency has to be below 10% (ideally 0%, but most people can live with a little aliasing at such low contrast).
To calculate the MTF of just the sensor at any given spatial frequency, the general
formula is (sin(pi*a*f))/(pi*a*f), where a is pixel width in microns
and f is the spatial frequency in cycles/mm (a black line next to white constitutes one cycle). The Nyquist limit for the
sensor is the spatial frequency of f=1/(2*p).
To then calculate the MTF at the Nyquist frequency for the simple case of 100% fill factor
(a=p), it comes to (sin(pi*a/(2*a)))/(pi*a/(2*a)). Which is the same as
(sin(pi/2))/((pi/2). The end result is 64% MTF at Nyquist. That is far higher than 10%, and will alias badly. But if you reduce the fill factor below 100%, the MTF increases, and aliasing gets worse and worse.
The OLPF reduces contrast at the Nyquist frequency to reduce aliasing.
...one can do a low pass filter in post processing, so why does one need an optical one?
Because by then it's too late. A 12.8 MP file from a full frame camera should only contain detail up to a certain spatial frequency: 40 lp/mm (using 3 pixels per LP). If you don't have an optical filter, then it will actually contain details that are supposed to be too small for it to see, such as 60 lp/mm. But once they are in the file, there's no way to know which details are too fine and which are normal.
But let's say you have an ideal OLPF. Then the file will contain details at 40 lp/mm and below: nothing above that whatsoever.
Now what happens when you downsample? If you use a point filter and downsample to 3.6 MP, you keep the 40 lp/mm details, even though the smaller file is not supposed to have them. Look at this image, for example:
http://thebrownings.name/photo/2009-10-aliasing/2009-01-30-3481-rt-400-point.png
See the dots of stubble on his face? You're not supposed to see that! The stubble is so small that all you should see is a slight gray blur, not individual hairs. The reason you can see them (as you know) is that I did not use a software low pass filter.
Now here is the same image, but with proper resampling:
http://thebrownings.name/photo/2009-10-aliasing/2009-01-30-3481-rt-400-lanczos.png
It's no longer possible to see individual stubble in sharp detail, but the gray blur is there.
So you are right that we can use a low pass filter in software, but only over the frequencies that are *already* in the image file itself. The problem is that unless you have an optical filter, the file will contain frequencies that are too high to begin with.
btaylor
11-16-2009, 12:26 AM
Of course, it all makes sense now since reading that last post Daniel! You point the front of the long tubey thing at whatever you want to take a picture of and press the button on top of the black square box. [:P]
Brian
Great Review! It gives me a lot to think about for getting one for wild life and action to complement a 5D Mk II.
Jon Ruyle
11-16-2009, 04:41 PM
Thanks, Daniel, for another detailed answer.
I guess part of my problem is that I was using the word "aliasing" wrong... I thought it referred only to specific types of artifacts caused by box-like sampling. The wikipedia article helped.
the general
formula is (sin(pi*a*f))/(pi*a*f)
This shows you need a *lot* more sampling to reduce aliasing. Much more than I would have thought.
So you are right that we can use a low pass filter in software, but only over the frequencies that are *already* in the image file itself.
Yeah I figured that after I wrote it and felt silly [:$]
If you use a point filter and downsample to 3.6 MP, you keep the 40 lp/mm details
I guess this is why people use a point filter to down sample. I always thought they did it because they were stupid. But, as you say, some people *want* to see aliasing.
I recall an article by Ken Rockwell in which he compares the 5DII to the D3x and concludes that the 5DII sucks because it isn't as sharp. Aside from a few obvious issues with this comparison (like the fact that he only compared jpegs), it seems also that he does not consider sharpness vs aliasing a trade-off... maybe it is time for a myth-busting thread about "per-pixel sharpness" (except, I suppose, that Ken Rockwell probably doesn't read this forum [:)])