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Author Topic: Can I find out the cause of the RAW blur?  (Read 1050 times)

Doug Peterson

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Re: Can I find out the cause of the RAW blur?
« Reply #20 on: June 11, 2019, 09:58:04 pm »

It was a 150mm lens, a medium telephoto (93mm equivalent).

Indeed. Must have misread the screen grab in my sleep deprived state.

Still, recomposition is not a meaningful factor at the distance with this amount of recomposition.

Stephen G

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Re: Can I find out the cause of the RAW blur?
« Reply #21 on: June 12, 2019, 01:53:29 am »

Nobody has mentioned it, so here is another possible cause of the softness: air/heat shimmer.
(Edit: apologies, just noticed that BobShaw mentioned it a few posts back)

Shoot faster to freeze it. Or, if the light isn't changing too quickly, take a few shots and pick the one with the least shimmer
« Last Edit: June 12, 2019, 02:03:36 am by Stephen G »
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spassig

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Re: Can I find out the cause of the RAW blur?
« Reply #22 on: June 12, 2019, 07:34:49 am »

@all
Thanks for feedback.
Today I have send the RAW to PO and discuss the picture.
PO is sure it's not a problem with focus.
It's vibration.
We also discuss some recommendations from this thread.
I will consider them in the future.
I hope make better technical pictures in Danmark were I go tommorow.
Small picture without vibration  ;)

Jochen
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Gigi

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Re: Can I find out the cause of the RAW blur?
« Reply #23 on: June 12, 2019, 08:57:24 am »

Not sure what to make of the new image - its soft - but is that because of the reduced size to post it? Is it possible to post some full size crops?
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Geoff

Bart_van_der_Wolf

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Re: Can I find out the cause of the RAW blur?
« Reply #24 on: June 12, 2019, 09:09:00 am »

@all
Thanks for feedback.
Today I have send the RAW to PO and discuss the picture.
PO is sure it's not a problem with focus.
It's vibration.

Yes, that's what I concluded as well. But the strange thing is that it appeared to be more horizontal than vertical. That's strange for camera/shutter-induced motion. Hence my suspicion that wind or some other external force had something to do with it.

Have fun in Denmark.

Cheers,
Bart
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== If you do what you did, you'll get what you got. ==

spassig

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Re: Can I find out the cause of the RAW blur?
« Reply #25 on: June 12, 2019, 09:20:50 am »

Yes, that's what I concluded as well. But the strange thing is that it appeared to be more horizontal than vertical. That's strange for camera/shutter-induced motion. Hence my suspicion that wind or some other external force had something to do with it.

Have fun in Denmark.

Cheers,
Bart

You have eyes like a eagle :)
I don’t find the different between horizontal and vertical.
I don‘t remember of windy morning.
Maybe I don’t have fix all connections after first AF shoot.

Jochen
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spassig

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Re: Can I find out the cause of the RAW blur?
« Reply #26 on: June 12, 2019, 09:42:16 am »

Not sure what to make of the new image - its soft - but is that because of the reduced size to post it? Is it possible to post some full size crops?
Thanks.
I show it that I can shoot sharper pictures, funny :)

Jochen
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anwarp

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Re: Can I find out the cause of the RAW blur?
« Reply #27 on: June 13, 2019, 03:35:05 am »

Perhaps the process of switching from AF to MF caused the focus to shift slightly?  Some lenses use a push-pull mechanism of the focus ring to achieve that.  I would suggest using the back button for AF, the. You can focus and recompose much more easily.
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ErikKaffehr

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Only good way to achieve correct focus...
« Reply #28 on: June 14, 2019, 06:41:52 pm »

Hi,

The only way to achieve correct focus is using live view at actual pixels at shooting aperture.

Anything else is a proxy. May be a decent proxy or not.

Best regards
Erik
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Erik Kaffehr
 

Doug Peterson

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Re: Only good way to achieve correct focus...
« Reply #29 on: June 14, 2019, 11:21:43 pm »

The only way to achieve correct focus is using live view at actual pixels at shooting aperture.

Anything else is a proxy. May be a decent proxy or not.

What a nonsense absolutest statement from a normally logical and non sensational guy.

There are many workflows that can consistently result in correct focus.

For example the XF Hyperfocal Tool will consistently be accurate to a single motor unit which is far finer than your hand during manual focusing in live view. It also has the benefit of being faster and easier to use and far more resistant to human error.

ErikKaffehr

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Re: Only good way to achieve correct focus...
« Reply #30 on: June 15, 2019, 02:21:30 am »

Hi Doug,

I would maintain that an AF-sensor in a different optical path is a proxy of the real sensor. For definition of proxy, check wikipedia: https://en.wikipedia.org/wiki/Proxy

Also with live view, you can choose any point to focus on. With AF on medium format you are pretty limited to a central part of the sensor.  The focus/recompose method induces some geometric error. You can correct that with calculations in the camera using with gyros to detect rotation.

Most lenses also have field curvature, that varies with focus distance. Focusing using live view uses the actual image and you can focus on the exact point that you want to focus on. So, it is as good as it can get. But most lenses also have focus shift. Therefore optimum focus needs to be made at shooting aperture.

But:

  • It is quite possible that Phase One has engineered around all those issues.
  • The point you make on accuracy on focusing ring vs. AF actuator is an interesting one. It is quite true that many AF lenses are difficult to focus manually.

Best regards
Erik


What a nonsense absolutest statement from a normally logical and non sensational guy.

There are many workflows that can consistently result in correct focus.

For example the XF Hyperfocal Tool will consistently be accurate to a single motor unit which is far finer than your hand during manual focusing in live view. It also has the benefit of being faster and easier to use and far more resistant to human error.
« Last Edit: June 15, 2019, 02:36:09 am by ErikKaffehr »
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Erik Kaffehr
 

Doug Peterson

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Re: Can I find out the cause of the RAW blur?
« Reply #31 on: June 15, 2019, 10:34:45 am »

Thanks, I know the definition of proxy.

I was disagreeing with your use of the word “only” in “live view is the only way to achieve correct focus”

It’s just flat out wrong to say that. Live view is very often a great way to focus. But there are many ways to achieve correct focus. In many cases live view isn’t even the fastest, easiest or most consistent.

ErikKaffehr

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Re: Can I find out the cause of the RAW blur?
« Reply #32 on: June 15, 2019, 12:45:36 pm »

Hi Doug,

Thanks for your comments.

That said, it seems that the OP missed something, which may be diagnosed as bad focus. Looking at the real image coming of the sensor at actual pixels, I don't think it can be bad advice.

I don't know how exactly the XF can focus, and I have not seen any test of focus accuracy on the XF.

With say the Fuji GFX we are in better shape, as Jim Kasson has made a lot of excellent testing on that camera.

Just as an example: https://blog.kasson.com/gfx-50s/fuji-63-2-8-focus-shift-and-autofocus-accuracy/

A system like Nikon D850 shows another picture:




From the same test. Sony A7rII has less issues:


I have never seen such tests with Phase One.

In the figures above, you wouldn't like to have the CoC exceed say 1.5 times the pixel pitch.

As I said, I have not seen any tests like that on Phase One. Jim only tests things he plans to buy.

Best regards
Erik


Thanks, I know the definition of proxy.

I was disagreeing with your use of the word “only” in “live view is the only way to achieve correct focus”

It’s just flat out wrong to say that. Live view is very often a great way to focus. But there are many ways to achieve correct focus. In many cases live view isn’t even the fastest, easiest or most consistent.
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Erik Kaffehr
 
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