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A7r IV and sharpness

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woodrim View Drop Down
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Post Options Post Options   Quote woodrim Quote  Post ReplyReply Direct Link To This Post Topic: A7r IV and sharpness
    Posted: 05 January 2020 at 01:09
A friend and near neighbor has bought the A7rIV and isn't getting very sharp images. It isn't an AF issue since he is only using MF lenses at this point. I don't think it's the lenses. I've heard about the sensor being unforgiving to camera movement, even with IBIS but I don't think this is that problem.

I'll be going through his settings, looking for anything obvious. I'll also turn off IBIS just to see if it may be defective. I'm wondering if anyone here uses it with MF lenses or have experienced similar issues.

His image look acceptable until starting to zoom in, then don't hold up - the opposite of what I would have expected. Any ideas?

I will test it myself with an old lens that is razor-sharp.

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woodrim
 



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addy landzaat View Drop Down
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Post Options Post Options   Quote addy landzaat Quote  Post ReplyReply Direct Link To This Post Posted: 05 January 2020 at 02:20
Lenses made for film might not resolve the 61mp of the A7r4. 24mp is about what a film can do, specialist films a little better. The best of the best film era lenses did not have to resolve 61mp.

At 61mp small focus errors become a bigger issue then at 24mp or 42mp. How does your neighbour focus? Does he zoom in for focus? Did he use a tripod? What is the f-number?

Did you check the settings?

Without pictures it did not happen With an example it is easier to help you(r neighbour).
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pegelli View Drop Down
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Post Options Post Options   Quote pegelli Quote  Post ReplyReply Direct Link To This Post Posted: 05 January 2020 at 08:42
Also when comparing 1:1 crops you need to realise a 60 MP image is blown up more than 42 MP and that one again more than 24 MP. So to compare the sharpness vs. older cameras you need to magnify less to compensate for that effect.

Also make sure the IBIS is set for the correct focal length (when using MF lenses that don't communicate with the body)
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Post Options Post Options   Quote Jonas A-R Quote  Post ReplyReply Direct Link To This Post Posted: 05 January 2020 at 08:46
At the same display size it should be sharper than an image from a sensor with larger pixels everything else equal.
61MP is not anywhere near oversampling even a modest kit lens.
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Post Options Post Options   Quote nandbytes Quote  Post ReplyReply Direct Link To This Post Posted: 05 January 2020 at 09:42
Tbh without examples with more information i.e. the lens used, exif, etc it's all just speculation and hitting in the dark.
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Post Options Post Options   Quote rovhazman Quote  Post ReplyReply Direct Link To This Post Posted: 05 January 2020 at 11:04
Originally posted by pegelli pegelli wrote:

Also make sure the IBIS is set for the correct focal length (when using MF lenses that don't communicate with the body)

I would also guess that it is the IBIS. When I forget to update the focal length of my manual focus lenses I usually get images that look fine at full size, but when zooming in to 1:1 I can see some lack of sharpness.

As nandbytes said, if you give us an example with all the details, we may be able to give more relevant suggestions.
 



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Dr. Harout View Drop Down
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Post Options Post Options   Quote Dr. Harout Quote  Post ReplyReply Direct Link To This Post Posted: 05 January 2020 at 12:08
So far I've used my a7riv with 3 Loxia and 3 Batis lenses, along with a Sony 50/2.8 Macro and the Tamron 90/2.8 Macro. All are exceptionally sharp (something I was afraid of before owning the a7riv).
I used it with a Schneider-Kreuznach APO componon HM 4.5/90 and it is superb, indescribably sharp.
Not used it with other lenses yet.
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Post Options Post Options   Quote Dr. Harout Quote  Post ReplyReply Direct Link To This Post Posted: 05 January 2020 at 12:09
Oh, I forgot to mention that I've used the mentioned lenses with or without tripods, with or without SSS.
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Post Options Post Options   Quote woodrim Quote  Post ReplyReply Direct Link To This Post Posted: 05 January 2020 at 16:50
I'll know more tomorrow or the next day when I get to look through the options and take some teat shots. I was hoping to hear some recommendations for settings to look at or any experience folks have had with older, MF lenses.

I do not believe that 61mp out resolves film at 35mm. Not yet, maybe another 50% more dense will do it or come too close to argue. However, I don't want to enter a debate about film vs sensor.

Those that know me from my postings will know that I'm very experienced with MF lenses. I have many that are very sharp and others that are softer. It will be good to test with both. Once stopped down to f/5.6 to f/8, there becomes less difference. However, I plan to use my Vivitar S1 90mm first. That lens can keep up well with most of today's lenses and no problem with 61mp.

I am curious about the IBIS and any issues magnified by a dense sensor. If IBIS becomes a more sensitive issue (at slower speeds), it strikes me that we would then need to know the actual focal length of a lens. In the past, lenses were labeled to a close focal length or one better for marketing. I've read several times that the S1 90mm is actually 87mm. As I write this, I realize I'll have to consider that during my testing. I don't have much experience with modern lenses but suspect they also may not be labeled accurately. With my A7II, I have to choose an IBIS setting when my lens falls in between those offered. AN example if 58mm. I choose 60mm IBIS but for all I know, the lens could be close to 55mm. I haven't experienced any issues but my sensor is only 24mp.

If this camera was a DSLR, I might be more suspicious of the sensor alignment but in my limited understanding of the technology, I believe manual focusing with mirrorless happens right on the sensor, so there should not be any adjustments needed to sensor location.

Regards,

woodrim
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pegelli View Drop Down
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Post Options Post Options   Quote pegelli Quote  Post ReplyReply Direct Link To This Post Posted: 05 January 2020 at 17:08
I wouldn't worry about the IBIS setting a few mm off, it's not an exact science anyway with manual lenses since distance is another variable that the camera doesn't know. And in the end IBIS improves your chance of a sharp image at longer times, but it's not a guarantee.
My personal rule of thumb is to go down for normal distances, go up for macro.
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Post Options Post Options   Quote nandbytes Quote  Post ReplyReply Direct Link To This Post Posted: 05 January 2020 at 17:14
Originally posted by pegelli pegelli wrote:

I wouldn't worry about the IBIS setting a few mm off, it's not an exact science anyway with manual lenses since distance is another variable that the camera doesn't know. And in the end IBIS improves your chance of a sharp image at longer times, but it's not a guarantee.
My personal rule of thumb is to go down for normal distances, go up for macro.


recently was using my laowa 10-18mm with the IBIS set to 50mm. My shots were blurry till I corrected this to a close focal length setting (set it 14mm as mid of the range).

So I am not really the tolerances of this setting is
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Post Options Post Options   Quote addy landzaat Quote  Post ReplyReply Direct Link To This Post Posted: 05 January 2020 at 19:00
The proof that I've seen and found convincing was that film is comparable to about 24mp for high quality commercial available general use film. Better for high resolution film. Not that it is that important.

My point mainly is that 61mp is much more then 24mp, so, a lens that is fine on 24mp might fall short on 61mp. That is all. And therefore, it might be the lens he is using (that Vivitar 90mm seems good, both the Komine and Tokina versions).

Also, your technique might be fine, but what about your neighbour?

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Post Options Post Options   Quote sybersitizen Quote  Post ReplyReply Direct Link To This Post Posted: 06 January 2020 at 00:03
Originally posted by woodrim woodrim wrote:

I do not believe that 61mp out resolves film at 35mm.

I think it might easily do so, though that would depend on the film. Even if it doesn't, there aren't many scanners that provide true 6400PPI resolution in order to pull 61MP out of 35mm film, so it won't be easy to demonstrate.
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Post Options Post Options   Quote terryg Quote  Post ReplyReply Direct Link To This Post Posted: 06 January 2020 at 06:27
Hi everyone,

I haven't had time to be here recently - just wanted to add that for critical focus with MF lenses on high MP cameras such as a7R3 and a7R4 you really need to be using one of the camera's Focus Magnifier options.

Focus Peaking gives way too many false positives on focus.

All the best,
Terry

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