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In defense of ZA85 vs GM85

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Photosopher View Drop Down
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Post Options Post Options   Quote Photosopher Quote  Post ReplyReply Direct Link To This Post Topic: In defense of ZA85 vs GM85
    Posted: 05 November 2018 at 04:52
I'm not trashing the GM85. It's fabulous in all regards. Compared to the ZA, the GM is sharper at all comparable apertures. It has higher hit rate with Eye-AF, and the GM SSM focusing is a pleasure to use by comparison to the ZA D Clutch. But... The GM is known as (and I believe marketed as) a "Bokeh Master". I've seen comparisons of the GM bokeh to the Sigma ART 85 bokeh, and the GM is smoother and sweeter all around. Could there be another lens that trumps the bokeh of the GM?

Sharpness aside, it looks to me the ZA equals the GM at f1.4 bokeh, and is noticeably smoother at all other comparable apertures... and not just by a little. I typically shoot the 85mm's at between f2 and f4, to ensure DOF for both eyes in a portrait. And I noticed I wasn't getting the same smoothness from the GM that I had grown to appreciate from the ZA. I never put it to the test until now.

Again, no doubt the GM is sharper. That's not the point here. At reasonable print sizes, and web publishing sizes, I can't personally see any difference in the sharpness. But I can see a difference in the bokeh at those sizes. So point being, there is an argument in favor of the ZA being a preferred choice for typical publishing requirements. This style comparison is never addressed in standard lens testing where charts rule the day.

These are screen shots at 1200pxl with the magnifier at 100%. Click image to magnify. Comments welcome.

ZA85 vs GM85 bokeh comparison.

Edited by Photosopher - 05 November 2018 at 04:55
 



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Jonas A-R View Drop Down
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Post Options Post Options   Quote Jonas A-R Quote  Post ReplyReply Direct Link To This Post Posted: 05 November 2018 at 06:07
Bokeh aside, the Zeiss lens shows it age by the relatively high level of chromatic aberration wide open.
a9 a6300 21/2.8 Loxia 35/2.8Z 35/1.4Z 50/1.4Z 55/1.8Z 85/1.4GM 90/2.8G 12-24/4G 24-105/4G 70-200/4G 100-400/4-5.6GM 2x TC
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Post Options Post Options   Quote Photosopher Quote  Post ReplyReply Direct Link To This Post Posted: 05 November 2018 at 06:29
It's hard to but bokeh aside on a thread specifically directed towards bokeh.

But yes, what you say is true. I just have to question if those aberrations are apparent at typical publishing sizes, and if they are, do they diminish the image in any way? And then what of smaller apertures where I typically shoot? It's kind of like noise. To date, I've never had a single client reject or comment upon noise or chromatic aberrations.
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Post Options Post Options   Quote Jonas A-R Quote  Post ReplyReply Direct Link To This Post Posted: 05 November 2018 at 08:47
Letís not put it aside then. What we are looking at is longitudinal chromatic aberration aka bokeh fringing.
If you donít shoot wide open it might not be a biggie.
But it can certainly be awful to look at and is rather nice not to have to deal with. Apochromats are usually priced at a premium indicating that some people prefer not to have it and are willing to pay for it.
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Post Options Post Options   Quote C_N_RED_AGAIN Quote  Post ReplyReply Direct Link To This Post Posted: 05 November 2018 at 10:34
Good comparison. I was surprised to see the difference between 2.8 and f4. I also see the ca as Jonas notes but I doubt 99 percent of the public would notice it.   Thanks for the test!
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Post Options Post Options   Quote Macca Quote  Post ReplyReply Direct Link To This Post Posted: 05 November 2018 at 11:41
Interesting comparison, I`ve just bought the ZA and await it`s arrival.Prices are now ridiculously low second hand and I`ve waited a while.

If I sold most or all of my A mount glass I could afford to buy maybe a couple of GM lenses, there`s nothing I see there makes me want to.
 



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Photosopher View Drop Down
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Post Options Post Options   Quote Photosopher Quote  Post ReplyReply Direct Link To This Post Posted: 05 November 2018 at 13:55
Originally posted by Jonas A-R Jonas A-R wrote:

...What we are looking at is longitudinal chromatic aberration aka bokeh fringing.


I'm viewing on a 4K monitor, so these 1200pxl clips size out 5.5"x8.5". At this size, on the first ZA85 at f1.4 image, I can barely see purple fringe on the top edge of the magazine. And perhaps barely a green fringe on the tripod leg top lock (black blob above the bike). I have to consciously look for it. I understand there are other situations where it would be more or less apparent. This is only one possible scenario.

But what stands out to me more obviously is the difference in smoothness between the ZA and GM at f2-f4 where the tripod legs cross over the bicycle frame. To me, the ZA makes those transitions more appealing than the GM. The bokeh ball size of metal zippers on the red plaid suit cases is larger and softer with the ZA in every instance. All highlight edges seem more spread out and softer on the ZA.

If there is objectionable color fringing in there, I honestly can't see it with my old eyes on this sharp monitor at this viewable size. Surely the GM wins the technical contest. But the ZA, to me, has more curb appeal.
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Post Options Post Options   Quote Photosopher Quote  Post ReplyReply Direct Link To This Post Posted: 05 November 2018 at 14:21
Originally posted by Macca Macca wrote:

If I sold most or all of my A mount glass I could afford to buy maybe a couple of GM lenses, there`s nothing I see there makes me want to.


You could just about purchase used copies of the ZA85/1.4 and ZA135/1.8 for less than a new GM85 for $1800. I just sold my GM for $1600, still more than those two would cost.

Make no doubt, if you ever get the chance to shoot with the GM, it is phenomenal in all regards. How that would translate to your final image in any meaningful way is relevant.

I know others have different concerns. I get that, and share many of the same concerns. But bokeh quality for me is most useful in the smallest of images where sharpness can be sacrificed. It's a tool to separate subject from surroundings. And that's most needed in smaller images, to clarify. But larger images sharpness cannot be sacrificed. Not by resolution, nor by depth of field. So I'll be at a smaller aperture for larger images anyway, where most anomalies are defeated.

My advertising photography has taught me to shoot for size. I typically know in advance whether my shot is to be a small thumbnail or a banner on a web site, or printed large for interior display. I get the luxury of knowing. I understand most folks want a single image to cover all potential publishing sizes. The GM probably serves them best.
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Post Options Post Options   Quote Jonas A-R Quote  Post ReplyReply Direct Link To This Post Posted: 05 November 2018 at 14:24
Originally posted by Photosopher Photosopher wrote:

Originally posted by Jonas A-R Jonas A-R wrote:

...What we are looking at is longitudinal chromatic aberration aka bokeh fringing.


I'm viewing on a 4K monitor, so these 1200pxl clips size out 5.5"x8.5". At this size, on the first ZA85 at f1.4 image, I can barely see purple fringe on the top edge of the magazine. And perhaps barely a green fringe on the tripod leg top lock (black blob above the bike). I have to consciously look for it. I understand there are other situations where it would be more or less apparent. This is only one possible scenario.

But what stands out to me more obviously is the difference in smoothness between the ZA and GM at f2-f4 where the tripod legs cross over the bicycle frame. To me, the ZA makes those transitions more appealing than the GM. The bokeh ball size of metal zippers on the red plaid suit cases is larger and softer with the ZA in every instance. All highlight edges seem more spread out and softer on the ZA.

If there is objectionable color fringing in there, I honestly can't see it with my old eyes on this sharp monitor at this viewable size. Surely the GM wins the technical contest. But the ZA, to me, has more curb appeal.


I wonder if the difference in bokeh ball size is due to differences in focal length? What else would change the size?
I also see a bit of purple fringing under the catch light in the eye inset (which I assume is displayed at 100%)
a9 a6300 21/2.8 Loxia 35/2.8Z 35/1.4Z 50/1.4Z 55/1.8Z 85/1.4GM 90/2.8G 12-24/4G 24-105/4G 70-200/4G 100-400/4-5.6GM 2x TC
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Post Options Post Options   Quote Photosopher Quote  Post ReplyReply Direct Link To This Post Posted: 05 November 2018 at 15:04
Originally posted by Jonas A-R Jonas A-R wrote:


I wonder if the difference in bokeh ball size is due to differences in focal length? What else would change the size?


I guess it could be. The ZA seems a tad bit more tele. But I thought it could also be attributed to the nature of each lens, just how they render. I could be wrong. Is bokeh ball size determining factor only related to the focal length?

Originally posted by Jonas A-R Jonas A-R wrote:

I also see a bit of purple fringing under the catch light in the eye inset (which I assume is displayed at 100%)


Yes no doubt at magnified 100% it is apparent. I almost left out the magnifier. Tempted to leave this sample as just bokeh comparison alone. But it's a system. Nothing acts in isolation, and I knew the topic would be raised at some point.
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Post Options Post Options   Quote sybersitizen Quote  Post ReplyReply Direct Link To This Post Posted: 05 November 2018 at 15:53
Originally posted by Photosopher Photosopher wrote:

Originally posted by Jonas A-R Jonas A-R wrote:


I wonder if the difference in bokeh ball size is due to differences in focal length? What else would change the size?

I guess it could be. The ZA seems a tad bit more tele. But I thought it could also be attributed to the nature of each lens, just how they render. I could be wrong. Is bokeh ball size determining factor only related to the focal length?

We don't see the shutter speeds in those shots. Are they where they should be, showing that the marked f-stops really are the same in both lenses?
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Post Options Post Options   Quote Photosopher Quote  Post ReplyReply Direct Link To This Post Posted: 05 November 2018 at 16:39
Yes of course. Extraordinary claims require...

Here's a Google Drive Folder with all files full resolution. JPG saved 7 from the RAW.
It's open for download
HERE

Settings for both lenses at iso 400:
1/800 @ f1.4
1/400 @ f2.0
1/200 @ f2.8
1/100 @ f4.0
1/50 @ f5.6

All shot Sony a7RIII. ZA adapted with LA-EA3.

While rendering these JPG's, I noticed the smaller apertures are larger files than the wide open apertures. If this indicates more information due to more detail, then it's interesting that the GM f1.4 JPG is slightly larger at 1.9mb than the ZA f1.4 JPG at 1.8mb. The GM f5.6 JPG is 2.3mb vs the ZA f5.6 JPG at 2.1mb. I don't know if it means anything. But it is a thing nonetheless.
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