Tom
thanks for the test, even though it isn't done right. If this flamefest hasn't put you off trying to do it again to get a more explicit outcome, may I suggest that you observe the method that I suggested above, and also take several shots with each camera and focus using 10x liveview BETWEEN EACH SHOT. That way you are likely to find a pair that are identically focussed and they will provide an excellent comparison which will be gratefully appreciated here.
brainiac wrote:
To make a fair comparison you need to shoot the same shot with each, even if that means stepping backwards.
In that case you would be testing the 21mp FF sensor from 5DII against the 18mp crop sensor from the 7D. Very interesting for many users. But the test that the OP did shows here is equally interesting cause we can see the crop-factor's advantage (if there is any) over the FF in reach.
I can't see any advantage of the 18mp the 7D has over the 8mp that 5DII offers for the same subject, and that is pretty useful to me as a buyer
If the test is done by using the same lens and moving the 5D closer to get the same framing, the difference in DOF would be apparent, which means 5D would have to use smaller aperture. People then will argue that the 5D might be softer because of diffraction or that the 7D is softer because it's wide open.
If the test is done by having the camera in the same position and by using different lens to minimise the FOV difference, people will argue that one lens is better than the other.
To make a fair comparison you need to shoot the same shot with each, even if that means stepping backwards. You then need to uprez the 7D shot to 21 Mpixels. From what I understand of what you have done here, there is no comparison to be made at all because (a) you have not taken the same picture with each camera and (b) you have not uprezzed the 7D shot to 21 Mpixels to ensure equivalent magnification of pixels (as would be seen in a pair of same-size prints).
Brainiac is absolutely correct. Use the same lens, same FOV and DOF, and uprez the smaller image (7d) to 21MP, but what you've done makes no sense at all. Perhaps Brainiac could comment on why we couldn't downres the 5d2, because it seems that that might work too.
I believe the only way to compare 100% images (i personaly am against it but...) is to position the 5d2 closer to the subject in a way that it has 18Mp covering the same subject framing as the 7D is !
That will mean that you can compare 100% vs 100% and get the exact same image.
Same lens, same aperture...only different DOF but thats inevitable.
If one can frame a subject suficiently far away the DOF becomes irrelevant and thus the test almost perfect.
And then, we will be comparing 18Mp vs 18Mp in a small vs larger (smaller than FF) sensor ! So the pixels ARE bigger but thats the advantage you get in a 5d2 over the 7D !!!
jamesf99 wrote:
Use the same lens, same FOV and DOF, and uprez the smaller image (7d) to 21MP, but what you've done makes no sense at all. Perhaps Brainiac could comment on why we couldn't downres the 5d2, because it seems that that might work too.
Orestis.Ch wrote:
In that case you would be testing the 21mp FF sensor from 5DII against the 18mp crop sensor from the 7D. Very interesting for many users. But the test that the OP did shows here is equally interesting cause we can see the crop-factor's advantage (if there is any) over the FF in reach.
Agreed, but this was not introduced as a test to see if or under what circumstances the extra reach of the 7D pays off. The reach test is going to be highly susceptible to lens limitations, so it's often not a test of cameras at all. Of course it's interesting to procure the very sharpest glass available and see if you can discern any reach advantage in the 7D, but it is probably more telling to use both cameras for something reach limited like, let's say, bird-in-flight photography, and see how well each camera does as part of the system i.e. lens, AF speed/accuracy, body, noise. This test is neither a good reach test nor was it introduced as a reach test.
> I can't see any advantage of the 18mp the 7D has over the 8mp that 5DII offers for the same subject, and that is pretty useful to me as a buyer
...notwithstanding that this test is focus-accuracy limited, and therefore hasn't necessarily shown the reach difference if there is one.
A reach test is a very specific kind of test, and is not often a good indicator of comparative performance in general use.
mactuna wrote:
I believe the only way to compare 100% images (i personaly am against it but...) is to position the 5d2 closer to the subject in a way that it has 18Mp covering the same subject framing as the 7D is!
That will mean that you can compare 100% vs 100% and get the exact same image.
...
And then, we will be comparing 18Mp vs 18Mp in a small vs larger (smaller than FF) sensor!
It is also important when athletes compete in the Olympics that you cut all their legs off by different amounts so that they are all the same height as the shortest fellow. That's the only way to see how they really compare as athletes.
On the contrary, the fair way to compare these cameras for general photography is to compare the whole frame of one camera against the whole frame of the other. You will not have to crop your 5D2 to 18 Mpixels in real use, so why should you disadvantage it that way in a test? The easiest and most reliable way to compare whole frames is to shoot the same shot with each, including image boundaries, and then uprez both files to a common number of pixels. Easy, fair, and predictive of differences in print.
vontom wrote:
Hi David,
It's just a simple comparison that I thought might be of interest or use to some.
Tom
It is useful to those who actually take pictures and occasionally have to upsize a crop body file to obtain a specific print size. Thanks for posting.
Don't get drawn into lengthly nit picking arguments with online forum measurebators .. look at their posting histories and see the extent to which they will grind a point into the ground. And all the while they can't see the forest for the trees.
Mike Mahoney wrote:
It is useful to those who actually take pictures and occasionally have to upsize a crop body file to obtain a specific print size.
Please explain how uprezzing a 5D2 image so that its 1.6 crop area matches the pixel pitch of the 7D tells you anything about the results you would see when you "upsize a crop body file to obtain a specific print size."
There's measurebating and there's endless surprise at the conflicting results of tests made with completely shoddy methods of comparison. I'll take measurebating and rigour over clueless mysticism.
Thanks for being definitive and articulating the differences. Giving accurate directions how to do a proper comparison is useful and helpful, to me at least. Again, thanks for the guidance.
ken.vs.ryu wrote:
same lens, same aperture, same location, crop the 5dII.
brainiac wrote:
Like you would with all your real photos.
BTW, perhaps I should explain that this comment of mine was an irony intended to point out why ken.vs.ryu's suggested method won't help in comparing real world camera performance. It's not fair to crop the result from one camera before comparing it to the uncropped result from another.
Even though this might not be the 100% perfect test it does show, to me at least, that there isnt the world of difference between 5DII and 7D that some people tend to lead us to believe.
brainiac wrote:
BTW, perhaps I should explain that this comment of mine was an irony intended to point out why ken.vs.ryu's suggested method won't help in comparing real world camera performance. It's not fair to crop the result from one camera before comparing it to the uncropped result from another.
cropping the 5dii will equalize what the lens transmits to the sensor.
brainiac wrote:
BTW, perhaps I should explain that this comment of mine was an irony intended to point out why ken.vs.ryu's suggested method won't help in comparing real world camera performance. It's not fair to crop the result from one camera before comparing it to the uncropped result from another.
It is if in the real world you are focal length limited. There is some merit to the comparison for the focal length limited shooter (i.e. one who cannot get closer to one's subject nor can afford a longer lens). This may not be everyone, but there are plenty of them, especially wildlife and bird photographers.
Allan Bruce wrote:
Even though this might not be the 100% perfect test it does show, to me at least, that there isnt the world of difference between 5DII and 7D that some people tend to lead us to believe.
Now imagine the image size of those two originals. The 5D2 image is huge by comparison. It started with more pixels, and then got uprezzed! By misunderstanding that issue you have proved my point that this is a very misleading comparison.
Perhaps Tom could show us the full frames of each camera so that people can understand a little better what they are really looking at, namely 2.4% of the 5D2 frame against 6.2% of the 7D frame (please correct me if I calculated that wrong).
