correcting color cast in X1D 2 images with Phocus

[wayne1]

What is the best way to correct color casts in Phocus? As I understand it, the Scene Calibration is to correct casts in images from technical cameras when using movements. How do do this with X1D images? A search on this topic did not help.

Wayne

[Charles2]

Adjust the white balance, for example by using its point selector on a white object in the image. Or do you have a different problem in mind?

[lorri12]

You need an LCC correction. To do this, hold a frosted glass ( LCC plate with matte side ) in front of the lens for each exposure and take an additional shot. Normally exposed about 2 f-stops higher ( via shutter, not via aperture ). It is correct: You offset this additional image via Hasselblads Phocus (scene calibration tool ) with the photo.
You're able to do this afterwards with the same aperture, shift and focus settings. But it's best to do it on the fly during shoot.

Photoshop does not offer this option!

Search for LCC correction on the web.

best regards
Lorenz, architekturfotografie-zh.ch

[JCM-Photos]

I made a lot of trials with numerous different lenses and tilt-shift lenses too.
LCC correction is only necessary with symetrical type technical lenses like Rodenstock, Schneider and other similar lenses.
I never saw on Optical complex FF TS lenses like Nikon (perhaps also Canon I didn't try) any coloured vignetting That is common with shifted symetrical lenses used on digital backs.

[lorri12]

That's interesting, thank you!

But the topic opener probably has the casting problem, otherwise he wouldn't ask.

I don't know the X1D, but the Sony CMOS certainly has this problem if you mount the camera on a technical camera or use HTS at best.

[JCM-Photos]

If you want a really perfect color rendition in Phocus you have to make a subject specific input ICC profile with a calibrated X-Rite SG chart.
Phocus is able to make such a profile by it's own and take account of the calibration data file of your chart.

It's quite difficult because lighting conditions of the chart are important, when some patches have glares the profile will be completely false with some weird false colors.
Also calibration datas are only valid a restricted time as the chart colors change in time and you have to recalibrate it.

[lorri12]

That is absolutely right and also my experience.

But it has nothing to do with colour cast as an effect on a view camera.

But thanks for the advice!

[JCM-Photos]

No camera can correct partial image color cast coming from the subject environment.
If you take a portrait with the head near to say a green fence, the face near the fence has a green color cast as the other half of the face will not.
The only way to struggle with this is to detect the situation when shooting and correct it in the field.
When this is not possible, a phocus layer with only half the face can esily correct the partial color cast.
Another problem can also come from mixed lighting sources, for example daylight and artificial where you have to make a choice when the artificial light cannot be tuned to the daylight.
Some non photographic artificial lights (like some street light) cannot be corrected for accurate colors, because they have heavy gaps in the visible light spectrum.

Otherwise, with a standard subject, a measured WB in Phocus on a grey card always gives accurate colors throughout the image using standard embedded profiles.

[wayne1]

Yes it is just a color cast I am trying to deal with, such as blue cast from a sky, but the above discussion is very interesting!  As far as  I can find, there is no color "picker" in the custom white balance tab in Phocus to select a true neutral gray or pure white as there is in ACR. Changing temperature and tint can get things close by eye, but is this the best way? In the camera, a picker is provided to select a neutral and set the white balance. I have not tried to see if this setting carries through the Raw conversion in Phocus, but it is not super convenient.

Wayne

[lorri12]

The white balance pipette is located below the image window, next to the alignment tool.

To correct individual colours, one can select the colour in the colour correction tool with the picker and correct it below with the 3 sliders with Hue etc..
The colour selection is a bit difficult and you can expand the region a bit with the fan in the colour wheel.

Some color problems are better to correct outside Phocus - for this I export e.g. in 16Bit tiff. But of course not the white balance.

hope I have understood the question correctly?

[wayne1]

lorri12

Thank you so much! This is exactly what I was looking for, and I am embarrassed that I did not look in the tool menu!

Wayne

[JCM-Photos]

Yes a custom WB made in camera is automatically used in Phocus when opening a RAW file.

in camera custom WB is very convenient when shooting in a place with a special WB setting and returning several times in this place, so you have just to recall the in camera stored special WB.