Below are two shots taken with the same lens, settings and processing in DPP (same recipe):
300mm f/4L IS @f/4, 1/4000s, ISO800.
Standard picture style, sharpening 1, no noise reduction or other corrections.
The 5D2 image was increased 150% in size on DPP conversion to achieve the same sized object in each photo when compared to the 7D.
I know that this is a one off test but should I be seeing more of a difference between the photos or is this about what can be expected in a comparison?
The 5DII image is on the left, judging by the DOF behind the subject, but what is the point? You've interpolated the data so the test is invalid - you've introduced another step. a whole other set of variables.
If you want a fairer comparison shoot the shot at two different distances so the subjects' image takes up the whole of the sensor on both
dhphoto wrote:
The 5DII image is on the left, judging by the DOF behind the subject, but what is the point? You've interpolated the data so the test is invalid - you've introduced another step. a whole other set of variables.
If you want a fairer comparison shoot the shot at two different distances so the subjects' image takes up the whole of the sensor on both
dhphoto wrote:
The 5DII image is on the left, judging by the DOF behind the subject, but what is the point? You've interpolated the data so the test is invalid - you've introduced another step. a whole other set of variables.
If you want a fairer comparison shoot the shot at two different distances so the subjects' image takes up the whole of the sensor on both
+ Graham's Number.
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).
vontom wrote:
It's just a simple comparison that I thought might be of interest or use to some.
It's just a quantifiably incorrect comparison that you didn't realise would mislead many.
I'm not trying to kill your love, but you must see that to share a comparison between two cameras you actually have to understand what you are doing and get the comparison right, otherwise you are sharing false information which misleads people who are trying to make buying decisions and undermines your own credibility amongst those who understand the errors you have made. Shoot the exact same scene, ideally a flat one, being careful to get the edges right, and then uprez the 7D image to 5D2 dimensions, or better still, to appease the superstitious, uprez both files to 8000 pixels wide, and show us the crops. Have some pride. You are not DPReview or DxO. You are better than that.
vontom wrote:
Hi David,
It's just a simple comparison that I thought might be of interest or use to some.
Tom
I'm quite sure it was done with the best of intentions
If you are trying to test one camera against another it's not the way to do it though because the 7D has all it's pixels in a much smaller area, so if you enlarge only a centre section of the 5DII file you are putting it at a huge disadvantage
If I were trying to do a real-world-test I'd fill the frame on both cameras and post un-interpolated versions side by side. The 7D image will be slightly smaller, but that's how it is in real life
alundeb wrote:
The DOF ought to be the same in those two images.
Only if the shots had been shown at their original sizes
No, as shown the DOF is equal. I don't want to argue about facts.
The test is valid as a test of wether the 7D has more "Reach" than the 5DII with this specific lens.
Sorry, but no it's not. If you enlarge one the circle of confusion has changed and they will not appear to have the same depth of field even if in reality they have. consider comparing a 6x4 enprint with a 10x8 from the same file or neg, the 6x4 enprint has more apparent sharpness even though in reality it doesn't
dhphoto wrote:
Sorry, but no it's not. If you enlarge one the circle of confusion has changed and they will not appear to have the same depth of field even if in reality they have. consider comparing a 6x4 enprint with a 10x8 from the same file or neg, the 6x4 enprint has more apparent sharpness even though in reality it doesn't
That depends if you are defining depth of field in terms of pixels or in terms of fractions of the image.
alundeb wrote:
David, you are on thin ice. Not only showing lack of understanding, but attacking a person (not me) behind a serious and meaningful reply.
Thats a great response. Lack of understanding yep, of course.
Not sure quite who you think you are, but I'm trying to help the OP to conduct a better test
brainiac wrote:
That depends if you are defining depth of field in terms of pixels or in terms of fractions of the image.
dhphoto wrote:
Why do you do that?
Why do you post such meaningless replies in the guise of being clever?
My reply explains the disagreement you and alundeb are having. If you define the depth of field as the locus of positions where the lens resolution satisfies the pixel resolution, then you get different results for different cameras even when the same lens is used from the same position. On the other hand, if you define the depth of field as being a locus of points which satisfy a certain resolution as a proportion of the image, then you mostly don't get a different result for the same lens at the same distance, regardless of camera used, assuming the cameras used are capable of resolving above the stated resolution. Typically when people discuss impressions of d.o.f. they mean the latter, but when they get calculators out and get nerdy about it they mean the former. That's the source of this pointless dispute about d.o.f..
But all this talk of d.o.f. is a red herring, not least because the two images aren't focussed on the same plane, so comparison of d.o.f. is extremely difficult or impossible.
