Lens cast correction

[BJNY]

Correcting color casts when wide angle lenses and/or
lens movements are used with technical cameras.
Wondering how each brand differs in use:
-Phase One's LCC
-Leaf's Custom Gain
-Sinar's white shading
-Hasselblad's Custom white correction

Would users and reps describe their procedures and opinions, please?


Thanks in advance for any replies.

Billy

[thsinar]

Here my feedback, although I had explained it in another thread. Better to have all together, to compare.

- Shoot the white shading with a diffusor/opal in front of the lens /Shoot your image(s)
- Import the files
- activate the "Shading Mode" ---> the file(s) in the contact sheet can then be marked as "White Shading"
- mark the white shadings in the upper left "click-box" (see screenshot 1)

- this marked "white shading" file will be applied to all following images in the contact sheet, UNTIL ...
- .... another file is marked as white shading, which will itself be applied to the next following files, until ...
- ... and so on ...
- drag these files in any folder of your choice ---> it will create new DNGs  with the shading applied (or one can export and create then TIFs or JPGs with shadings applied)

The process/feature, when activated, greys-out the files selected, puts a "separator" between the files having a different shading file applied, making it an easy visual control. Files can be de-selected, if for example one does not want the shading to be applied to a particular image included in the sequence.

In addition to this, there is another feature, the "Vignetting Correction" tool, which can be applied at the same time, when the shading process takes place, with different strength: NONE, 25%, 50%, 75% or 100% (see screenshot) 2.

IMO a very workflow orientated "Shading" tool, which saves hours of work, since it is batch-processed and automatic, on as many files one wishes.

Best regards,
Thierry

Edited for Addendum: the shading tool obviously works tethered and un-tethered

Correcting color casts when wide angle lenses and/or
lens movements are used with technical cameras.
Wondering how each brand differs in use:

-Sinar's white shading

Would users and reps describe their procedures and opinions, please?

I recall:

-Sinar now has vignetting control as well.

Thanks in advance for any replies.

Billy

[jonstewart]

Hi all
I'd be really interested in whether anybody has an opinion on whether the wavelength of the light entering the lens has any significant effect on the colour cast produced.

I've read about people who, like Thierry, shoot a LCC (or whatever other brands call it) along with their session of shots, and those who do a set of LCC's in the studio, for each value of aperture/rise/fall/shift/tilt etc and then apply to other shots.

Any links or pointers to other threads welcome.

TIA

[clawery]

1.  Capture the LCC by placing the calibration plate over the front of the lens (you may have to open up 1.5 -2 stops)
2   While in Capture One software, click on thumbnail of image and white balance.
3.  Save the LCC with a corresponding name to the image that it will be applied to.
4.  Click the image or images that you will need to apply the LCC to and go the drop down list of calibration files and apply the file to the images.

[attachment=11524:Picture_1.png]


[attachment=11525:Picture_2.png]

Chris Lawery
Sales Manager
chris@captureintegration.com
Capture Integration, Phase One Dealer of the Year

877-217-9870 | National
404-234-5195 | Cell  
Sign up for our Newsletter | Read Our Latest Newsletter

[BJNY]

1.  Capture the LCC by placing the calibration plate over the front of the lens (you may have to open up 1.5 -2 stops)

Thanks, Chris.

Isn't it better to keep the aperture the same between LCC and actual images?
So, slow down the shutter speed 1.5-2 stops
OR
increase the strobe output by 1.5-2 stops (when using flash inside studio)
Correct?

Does Capture One also correct lens falloff (vignetting) when a center filter isn't used on a Digitar?

[jonstewart]

Chris,
Surely the point is that the cast is partly dependent on the aperture?  

@BJNY

In my experience the LCC doesn't correct for falloff, and I use a CF as a result. I'd be interested in hearing any other nifty and efficient solutions to correcting fall off though

[DavidP]

Thanks, Chris.

Isn't it better to keep the aperture the same between LCC and actual images?
So, slow down the shutter speed 1.5-2 stops
OR
increase the strobe output by 1.5-2 stops (when using flash inside studio)
Correct?

Does Capture One also correct lens falloff (vignetting) when a center filter isn't used on a Digitar?

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.

[jonstewart]

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.

So David, chroma noise is independent of ISO?

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

[DavidP]

So David, chroma noise is independent of ISO?

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

The Phase One only LCC only corrects the color shift, not anything else like light fall off from wide angle, I have not seen any problems using 100 or 200 for the LCC when using 50 for the main exposure.
I had not thought to test it scientifically either but it seems to work fine. The final files are very clean. I am not sure if it would be different with some of the other systems.

[jonstewart]

Thanks David,

It seems intuitive that that would be the case, but I must test same, the question having been raised.

(I'm shooting a P45 on Bicam/Schneiders)

[thsinar]

I would recommend to use the same f-stop, of course, with the same camera movement (shift, tilt or swing or whatever), obviously.

In this respect, let me say that this "Shading" tool has been developed with the help and instructions of Rainer Viertlböck: he can certainly jump in and give the reasons what is the idea and why it has been done the way it is, needing himself and using shadings on a daily basis. I think he may have much more to say, from a practical point of view.

Best regards,
Thierry

Isn't it better to keep the aperture the same between LCC and actual images?
So, slow down the shutter speed 1.5-2 stops
OR
increase the strobe output by 1.5-2 stops (when using flash inside studio)
Correct?

[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.

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

[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

[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?

[jonstewart]

Interesting, BJNY,

I wonder does it handle the asymmetrical vignetting that you get with a shifted shot?

.. and yes, would love that for Phase one.

Cheers

[thsinar]

Dear John,

the Sinarback and eXposure software can do this as well, opening a corrected (shading and/or vignetting correction) file directly in LR, Aperture, ACR, etc ...,all DNG compatible applications. No problem at all.

Do you know if the Leaf software can apply the shadings (gain adjuster) on as many files as wished, automatically, with the right shading to the right files, in a batch process?

Best regards,
Thierry

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

[thsinar]

Yes, absolutely correct Billy, of course, otherwise it would not make much sense for an efficient workflow.

And of course, the shadings can be saved for further use, but that goes without having to mention.

But 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

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?

[thsinar]

Jon,

yes, it does, since the vignetting correction is included in the shading file, and can be applied, with different strength, or not. If not applied, then only the color cast is corrected.
This is also a must, if one wants efficiency and an optimal and fast workflow.

Best regards,
Thierry

Interesting, BJNY,

I wonder does it handle the asymmetrical vignetting that you get with a shifted shot?

.. and yes, would love that for Phase one.

Cheers

[rainer_v]

I would recommend to use the same f-stop, of course, with the same camera movement (shift, tilt or swing or whatever), obviously.

In this respect, let me say that this "Shading" tool has been developed with the help and instructions of Rainer Viertlböck: he can certainly jump in and give the reasons what is the idea and why it has been done the way it is, needing himself and using shadings on a daily basis. I think he may have much more to say, from a practical point of view.

Best regards,
Thierry

the shading plug-in was planned as part of the artec poject. From the beginning of the artec project i insisted that an adaequate software solution has to be part of the project and i was asked to implement its features and how they should work with the software crew by sinar. - it does not make much sense to create an architecture camera without thinking in the software which has to correct the unsymmetric shifts and fall offs of the lenses.
For me the workflow is beside the file quality the key point for such setup ( for the camera as for the sw ). the white shading plugin in exposure allows very fast and logic batch processing of the files. As in the brumbaer tools before the intent is to allow an intuitive batch workflow, where you can do other things meanwhile the program corrects the colorshifts / light fall offs. Further i.m.o. its a must that these files can be converted afterwards in third party konverters.
Btw. because the color shifts and the vignetations can be softened ( as long you dont (ab)use them to correct other issues as centerfold ) there is absolute no noise added, equally in which iso setting and with which exposure time one creates them.  The emotion75 backs allow absoulte noisefree exposures till 32 seconds, with and without white shadings.

[clawery]

Chris,
Surely the point is that the cast is partly dependent on the aperture?  

@BJNY

In my experience the LCC doesn't correct for falloff, and I use a CF as a result. I'd be interested in hearing any other nifty and efficient solutions to correcting fall off though

Jon,

If you don't want to adjust with the exposure with opening up the aperture, you can either do it with shutter speed or possibly in the Capture One software.  From one of the other posts it sounds like you adjust the ISO, but I have not tried that personally.

Chris Lawery
Sales Manager
chris@captureintegration.com
Capture Integration, Phase One Dealer of the Year

877-217-9870 | National
404-234-5195 | Cell  
Sign up for our Newsletter | Read Our Latest Newsletter