Scott Stoness Offline Upload & Sell: On
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Some things to consider:
1) The sony 24-70 is corrected in camera (and it changes the raw I believe) for vignetting and barrel distortion. So you might be comparing apples to oranges. If I am wrong about raw change and its changed in software conversation you will get the same results.Use an adobe raw converter and turn off lens corrections to compare apples to apples.
2) Its possible that you are focusing different on canon vs sony. What setting are you using on both?
3) The 24-70 v2 is not as good as people make it out to be. It is a good lens but it is not a prime. This shows up more on 36mpx. Eg from photo zone.de 3531 at centre and 2613 at edges is a very wide gap at 24mm/f2.8. It also has 2.83% barrel distortion which will cause the edges to have distortion. Contrast this with the reference lens ts24, 3740, 2942 and 0.884 barrel, and you should expect to see some edge degradation. The important difference here is the ratio between them, the ts24 will likely get >4000 on both measures whereas the 24-70 will have the edges under 3000. And the degree of barrel distortion really matters too - the 17-40 has really high barrel distortion and this leads to its low performance on edges.
http://www.photozone.de/canon_eos_ff/773-canon2470f28mk2ff?start=1
http://www.photozone.de/canon_eos_ff/603-canon24f35tse2?start=2
4) Where/how you focus really matters. If you are using the a7r, you must be using it for mpx. Otherwise stick with the 5diii because its better in almost every dimension except dynamic range under iso800 and mpx. I use manual focus, zoomed in with peaking. To compare you have to focus on the same spot with zoomed in manual focus.
5) None of the metrics related to 70-200 that you have read likely talk about field curvature. Some lens focus forward (focus centre and curved forward), some backward (focus centre and curved back). You have to understand your lens to gain maximum focus. This will show up more at 36mpx. So even if you focus on the same spot, you might conclude that one is sharper than the other when its not necessarily true. Maybe the left and right are close in on sony lens and it focusses back.
6) The other issue with lens is that, they are focussed wide open and then closed down as the picture is taking. Some lens change their focus distance as they are closed down (focus breathing). I don't think this is an issue with the 24-70 but who knows if the a7r misfocusses and then the sony 24-70 is focused differently, it might correct for a misfocus.
7) My own experience, with my 17-40 when I compared it to my zeiss 25/2, 24-70v1, 24-105, sony 24-70, Ts24 was that it was by far the worst lens in my collection. I think my 17-40 was decentered and I did not notice when I used it on my 5diii way many years ago. The point is that you might also be finding something wrong with your 24-70 or the tolerances on your 24-70 are canceling with your body that you had before.
8) its also possible that your a7r mount is misaligned and this is causing problems.
Why don't you borrow a ts24 and manually some focus point on a7r/metabones and 5diii and compare to find out if its your metabones. Pick a scene where the left and right side of the image is the same distance as the centre (eg. far away mountain range with trees for contrast).
[Or maybe you just need to try a 4rd metabones because everyone else is bringing them back and all that are left are decentred.]
Edited on Dec 22, 2014 at 11:45 AM · View previous versions
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