Here's what my copy's focus shift looks like on an infinity subject. Both were focused on the A7rII at their respective apertures - the A7rII focuses this lens wide-open vs stopping down:
jamato8 wrote:
Try it on continuous focus. My 1st copy did that and would work on continuous focus. I sent it back.
Thanks. AF-C switches the A7rII to use stopped-down focusing, which matches the A7s's AF-S operation and corrects for the shift. Interesting to hear of another copy with the same behavior. I suspect the posters on the dpreview thread have the same issue as well. I wonder what percentage of copies are affected.
snapsy wrote:
Meh, seems par for the course for me. Btw, I see you and others posted corner crops - I'm usually more interested in edge performance, since most of my landscape need sharp edges but don't have anything in the corners, at least not the upper corners. How is your copy at the edges? Mine doesn't seem that impressive, esp considering the accounts here of the lens being sharp across the frame even @ f/4. Here are mine - focus is on far hills, which is what I'm using to evaluate the center vs edge performance.
They definitely look somehow soft. My copy is sharper, not right from 24 mm into the extreme corners but from 28 mm and up to 85. I agree with Fred, even center sharpness is not on a very high level...which is a bit unusual, seeing other posts and based on my personal experience.
Fred Miranda wrote:
Usually if a lens does well at the very extreme corner, it will do just as good or better at the edges of the frame (As in a regular landscape image). I need to check your full size images on my computer but at first look they look a bit soft even at center at some FLs. Is that where you focused?
I agree, that's usually the case but since this lens has already demonstrated unusual copy-specific characteristics it would be really nice to see how its edges performs, esp since those are within the frame more frequently than corners.
mjm6 wrote:
Bummer on that lens. I wonder if it is a problem in the firmware for the lens, or if it is a problem with an encoder or similar.
The lens is focusing correctly at each given aperture, so it can't be a firmware issue unless the design or manufacturing tolerance of the lens is expected to have focus shift, in which case the firmware should be instructing the camera to always use stop-downed focusing instead of only during AF-C (and assuming such instruction is possible over the E-Mount protocol).
GMPhotography wrote:
My guess it might be a element grouping out of whack
What's unusual is that in spherical aberration (focus shift), the focus plane is supposed to shift away from the camera at stopped-down apertures, ie at widest apertures the lens is front-focusing, which means the plane of focus shifts to the "correct" plane of focus further away when stopped down. On my copy the focus shifts closer to the camera when stopped down. Here is what focus shift looks like on the Canon 17-55 f/2.8 lens @ 55mm (part of optical design so it occurs on all copies):
Is this characteristic common only in sony lenses or does this happen with all manufactures..pretty disconcerting . If you are shooting group photos and want depth of field, say at f8+...you are pretty much screwed.
echelonphoto wrote:
Is this characteristic common only in sony lenses or does this happen with all manufactures..pretty disconcerting . If you are shooting group photos and want depth of field, say at f8+...you are pretty much screwed.
Focus shift is a common issue in some lens designs - it's not specific to Sony. The fact it appears to be copy-specific on this model is pretty unusual though.
snapsy wrote:
Focus shift is a common issue in some lens designs - it's not specific to Sony. The fact it appears to be copy-specific on this model is pretty unusual though.
Sony seems to be pushing the boundaries of optical design and manufacturing tolerance. We are starting to encounter odd issues never seen before.
If the case of your copy it will be hard to get sharp results unless capturing images at shooting aperture.
Fred Miranda wrote:
Sony seems to be pushing the boundaries of optical design and manufacturing tolerance. We are starting to encounter odd issues never seen before.
If the case of your copy it will be hard to get sharp results unless capturing images at shooting aperture.
I'm going to redo my full aperture landscape series in AF-C mode today to see how well the lens performs otherwise. It's definitely going back though, as soon as I can find another in stock.
Just joined that Sony pro membership....they sent me a loaner 16-35 2.8 within two days...nc...not too shabby. Unfortunately, its not a good copy..the 24-105 is def. better.
Here is a full test of my copy @ infinity. 100% crops from vertical center of frame (full width of sensor). I focused in AF-C, 3-samples per focal length/aperture with best selected. AF-C focus variability was surprisingly high.
My impressions:
24mm good, edges still a little soft even @ f/8
35mm very good, edges reasonably sharp @ f/8
50mm very good, edges reasonably sharp @ f/5.6
70mm good but edges very soft even @ f/8
105mm very good, edges sharp @ f/8
Just joined that Sony pro membership....they sent me a loaner 16-35 2.8 within two days...nc...not too shabby. Unfortunately, its not a good copy..the 24-105 is def. better.
Dang that’s a shame but I love the Pro service. I want the 24-105 I had as a loaner. Good copy
