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Author Topic: Lens cast correction  (Read 20271 times)
jonstewart
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« Reply #20 on: February 15, 2009, 11:28:52 AM »
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Thanks for the informative replies, all. Given me something to think about there.
Cheers
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Jon Stewart

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BJNY
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« Reply #21 on: February 15, 2009, 12:23:55 PM »
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Quote from: pixjohn
To  add a little more info, I went with Leaf because of the functionality of  the gain adjuster. Not only does it correct any color shifts with wide angle lenses,  It also corrects lens fall off. The other advantage if you shoot tethered you can upload the gain adjuster and have a correct file that can be opened  in Leaf LC, Lightroom Photoshop among other programs. What other back can do that?

John

John,

Would you mind detailing your procedure?
Wondering if you save a raw with vignetting correction first ,
then another raw with with vignetting & gain applied?

Thanks,
Billy
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Guillermo
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« Reply #22 on: February 15, 2009, 12:24:55 PM »
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Quote from: DavidP
When I need to add exposure to the LCC in Capture One I temporarily raise the ISO, So I don't have to mess with camera or strobe settings.

Thanks for the GREAT tip, David.
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Guillermo
David Grover / Phase One
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« Reply #23 on: February 15, 2009, 12:39:44 PM »
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Quote from: BJNY
Thanks to everyone for the replies so far.

John,
According to Thierry's post #2, Sinar's eXposure also allows
saving the white shading and/or vignette correction into the raw file as well.
Correct, Thierry?

Do Phase and Hasselblad users have or want this same capability?

Yes, the correction is saved into the Raw file.

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David Grover
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David Grover / Phase One
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« Reply #24 on: February 15, 2009, 12:41:34 PM »
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Quote from: fraherim
Hi,
For Hasselblad backs here is some info:
There is a feature in Phocus called Custom White Balance.
Here is the only instructions I've found on this:
Custom white correction

This feature allows you to correct for things like cast issues when using tilt and shift. User interface for this has been added to the lens correction tool. The procedure is as follows:

1) Make a calibration image of a neutral gray surface - the best results are obtained by using an opaque filter. The capture can be made either tethered or untethered.

2) The calibration image needs to be available as a 3F file so if it was captured untethered you will need to import it.

3) Load an image where you'd like to apply the correction

4) Select the thumbnail of the calibration image and click the Create button found in the Lens Correction tool

5) You will be prompted for a name of the correction - it's a good idea to use it to describe things like the lens and aperture used.

6) You have now created a custom white correction - to see it's effect on the currently loaded image check the Custom white checkbox.

7) To apply the custom white correction you can follow the same methods as when applying any other adjustment to a range of images using either the Modify dialog or the Modify Lens Corrections of Selected Files option in the Lens tool preset menu.

Cool If this correction is one that you might want to save for future use you can simply create a Lens Adjustment preset with the correction active.

This applies to Phocus 1.1 or later MAC ONLY.
The current Phocus for the PC does not have tis feature yet. We have to wait for version 1.1 to come out.
However if you are a PC person like myself the custom white balance feature does work on FlexColor.

One note:  I still use a translucent card over the lens like way I did it with my PhaseOne back.  I haven't tried the shooting a neutral gray surface yet.

I hope this helps,

Bob

Thanks Bob for saving me the trouble!

The improvement in Phocus with Custom White meant that untethered captures can now benefit from CW corrections whereas with FlexColor it only really worked with tethered captures until later on in its life.

It is much more straight forward with Phocus.

Best,


David
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David Grover
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BJNY
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« Reply #25 on: February 15, 2009, 12:45:28 PM »
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Quote from: David Grover / Hasselblad
Yes, the correction is saved into the Raw file.

Can it be "saved as" an alternate raw file
leaving the original raw intact for whatever reason?
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Guillermo
David Grover / Phase One
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« Reply #26 on: February 15, 2009, 01:00:35 PM »
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Quote from: BJNY
Can it be "saved as" an alternate raw file
leaving the original raw intact for whatever reason?

I haven't tried in practice but, yes you could have an uncorrected image and then a corrected one for comparison.

Especially if you have saved a library of CW shots.

David


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David Grover
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ericstaud
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« Reply #27 on: February 15, 2009, 01:38:17 PM »
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Quote from: jonstewart
So David, chroma noise is independent of ISO?

I ask because I've never thought to test that out.

The Chroma noise question is very interesting.  I have used both Phase and Leaf backs.

It is my understanding that if you shoot an image with low chroma noise but use a white reference frame with high chroma noise, then the noise which is corrected out of the reference file gets added into the image you are trying to correct in the end.  I can think of two examples... 1. shoot the image at 100 ISO and then shoot the reference file at 400 ISO. or 2.  Shoot the image at 5 seconds and then shoot the reference file at 20 seconds.

I believe that the color casts can be f-stop dependent, so I have always used a longer exposure, or a brighter light source to make the reference file.  If I am using strobes I can point a head at the lens after the main bracket is finished.  If I am shooting in sun, I will often turn the camera into the sun and don't change the exposure at all.  This last method also provides a great way to color balance an image.  If these two options aren't available I just make a longer exposure.

I would not be surprised if the fall-off correction of the Dalsa backs (both Leaf and Sinar) might also have the same effects on luminance noise as all the backs have on chroma noise with the color cast corrections.
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ericstaud
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« Reply #28 on: February 15, 2009, 01:47:41 PM »
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Quote from: David Grover / Hasselblad
I haven't tried in practice but, yes you could have an uncorrected image and then a corrected one for comparison.

Especially if you have saved a library of CW shots.

David

David, what do you mean the color uniformity correction is saved "into the file"?  If I open that file in Adobe Camera RAW is the color cast still there, or has the color cast been written out of the file entirely?
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BJNY
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« Reply #29 on: February 15, 2009, 01:53:46 PM »
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Eric,
Thanks! for chiming in.
« Last Edit: February 15, 2009, 01:59:25 PM by BJNY » Logged

Guillermo
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« Reply #30 on: February 15, 2009, 02:02:00 PM »
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Quote from: BJNY
Eric,
Thanks! for chiming in.


Thanks David.  I learned a lot about this topic on this site back in 2006 when I jumped in with both feet.
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rainer_v
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« Reply #31 on: February 15, 2009, 03:42:34 PM »
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yes, chroma and luminance noise is added with white shots if they are not softened.
 if the purpose of the white shots (as i said above) is only to correct lens color casts and fall off the white files can be softened a lot, cause the casts and fall off dont have sharp edges.
if the white files are softened enough there is no more L or Cr noise in them, independent of its iso or exp.times.
but this softening can not be done if the white files are at the same time used to correct issues which have sharp edges, as centerfolds or dust removal.
« Last Edit: February 15, 2009, 03:42:52 PM by rainer_v » Logged

rainer viertlböck
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BJNY
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« Reply #32 on: February 15, 2009, 03:55:53 PM »
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Hi Rainer,

How to go about softening?

Thanks,
Billy
« Last Edit: February 15, 2009, 04:06:28 PM by BJNY » Logged

Guillermo
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« Reply #33 on: February 15, 2009, 05:17:24 PM »
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Quote from: BJNY
Hi Rainer,

How to go about softening?

Thanks,
Billy
you cant do that. this depends on the method how the white shadings are created and applied by the different programs.
resulting quality is very different. workflos too, so its worth to take a real closer look to these programs. you can save hundreds(!) of hours and the quality and or limitations of these shadings can be very different. i.m.o. its a key feature if a back is used with shift lenses.
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rainer viertlböck
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thsinar
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« Reply #34 on: February 15, 2009, 06:10:42 PM »
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Billy,

What Rainer says, is that the purpose of the white shots in the Sinar eXposure is only to correct lens color casts and fall off and therefore the white files can be softened a lot (by eXposure, not by the user).

This simply because the "shading" tool in eXposure does NOT need to be used for "Centerfold", "Dust", etc ... issues: that's done as well, in eXposure, and automatically, BUT NOT in the shading / vignetting correction tool.

The question being if other applications are doing this (centerfold & dust removal) during the shading or not: some certainly are, from my knowledge, and in this case the shadings cannot be softened by the software.

Best regards,
Thierry

Quote from: BJNY
Hi Rainer,

How to go about softening?

Thanks,
Billy
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Thierry Hagenauer
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thsinar
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« Reply #35 on: February 15, 2009, 06:34:00 PM »
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This question remains unanswered for me, while it is the basic one to ask and to know and while this point is exactly what saves hours of work.

It is well understood that one can apply one particular shading to a number of selected images, but that's not relevant

If one has to re-start the shading process with each new shading to be applied (to other files needing a different shading), then the workflow is dramatically affected and hours of work are necessary: does anybody know if other application can apply different shadings to different images, automatically and in a batch?

Thanks,
Thierry

Quote from: thsinar
... More importantly is to know if the software can apply AUTOMATICALLY the shadings to as many files as chosen/available to be shaded, with the right shading applied: this is what saves time and what is important, and not having to apply one by one.

Best regards,
Thierry
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Thierry Hagenauer
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ericstaud
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« Reply #36 on: February 15, 2009, 07:29:48 PM »
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Quote from: thsinar
This question remains unanswered for me, while it is the basic one to ask and to know and while this point is exactly what saves hours of work.

It is well understood that one can apply one particular shading to a number of selected images, but that's not relevant

If one has to re-start the shading process with each new shading to be applied (to other files needing a different shading), then the workflow is dramatically affected and hours of work are necessary: does anybody know if other application can apply different shadings to different images, automatically and in a batch?

Thanks,
Thierry

Thierry, Phase one does not have a batch feature for lens cast.  I select the reference file, shift select the remainder of images in the bracket, click the LCC button and choose "analyze" from the pulldown menu (the correction is now created with and applied to the reference file), then shift+cmd+c, then shift+cmd+v will copy the correction and paste it to the remaining files.

I just tried this out for your reference, and it takes about 10 seconds per setup.  So if I shoot 20 setups in one day, then it takes 3 minutes 20 seconds to do the lens cast corrections.
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thsinar
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« Reply #37 on: February 16, 2009, 07:02:49 AM »
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Dear Eric,

thank you for the details how it works. I guess the "analyze" part does not take long, otherwise it would be some time time to wait until this is done, then applied with copy/paste, and then continue with the next shading file.

But anyway, can one then take these corrected files and go to any DNG application, or does one have to use C1?

Thank you very much,
Thierry



Quote from: ericstaud
Thierry, Phase one does not have a batch feature for lens cast.  I select the reference file, shift select the remainder of images in the bracket, click the LCC button and choose "analyze" from the pulldown menu (the correction is now created with and applied to the reference file), then shift+cmd+c, then shift+cmd+v will copy the correction and paste it to the remaining files.

I just tried this out for your reference, and it takes about 10 seconds per setup.  So if I shoot 20 setups in one day, then it takes 3 minutes 20 seconds to do the lens cast corrections.
« Last Edit: February 16, 2009, 07:04:52 AM by thsinar » Logged

Thierry Hagenauer
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« Reply #38 on: February 16, 2009, 08:09:50 AM »
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It has to stay in C1 you can make a variant of the original raw with the new corrections applied so in the C1 browser you can actually have both. You can also make a preset and save it for future use. Lot's of folks actually make a library with there lenses and the LCC corrections than name it for those conditions and than apply it for others as well. But yes to analyze only takes a couple seconds. Hold it I take that back you can process it to a DNG file. Just tried it and it opened right up in CS4 with ACR. I'm sure you can bring it into LR as well.
« Last Edit: February 16, 2009, 08:10:55 AM by Guy Mancuso » Logged

thsinar
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« Reply #39 on: February 16, 2009, 08:15:24 AM »
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so, if I understand it right, you make the corrections, file(s) by file(s), by creating first the shading with the "Analyze" function and then apply them to the files. And then you do the DNG conversion in C1 to finally open them in DNG compatible applications?

Quote from: Guy Mancuso
It has to stay in C1 you can make a variant of the original raw with the new corrections applied so in the C1 browser you can actually have both. You can also make a preset and save it for future use. Lot's of folks actually make a library with there lenses and the LCC corrections than name it for those conditions and than apply it for others as well. But yes to analyze only takes a couple seconds. Hold it I take that back you can process it to a DNG file. Just tried it and it opened right up in CS4 with ACR. I'm sure you can bring it into LR as well.
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Thierry Hagenauer
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