PHASEONE color profiling

[leonardobarreto.com]

I was doing my work today as usual with the P25/Mamiya at a gallery doing a series of monochromatic paintings and things where going well until the gallery director came with one that had a deep purple color almost blue. When I shot and compare it with the image on my PowerBook G4 the hue was more to the blue.

At this point I did't know what to do, but decided to try the only thing that could do something in correcting color -- besides balancing the white dot whit a gray card -- and bingo, the solution was just that.

The work was burned to DVD, handed to client, client was happy and "will call when there is more work to shoot"

But I realized that this is the corner of my learning curve that I have not yet learned, so, please, some one tell me how to color profile a P25 back??

But first I will finish my story. What I did was to change the ICC PROFILE from

1* PHASE ONE P 25 P GENERIC EASY GRAY
TO
2* PHASE ONE P 25 OUTDOOR DAYLIGHT
and also works
3* PHASE ONE P 25 PRODUCT FLASH

I was using flash, and before I had set the program to the first one (1*)

Here are the images. The first one is with "easy gray" and is blue

http://leonardobarreto.com/images/TEMP/example_2.jpg

and the other one is with outdoor daylight and is --judging from my portable display -- very close match to the original.
http://leonardobarreto.com/images/TEMP/example_1.jpg

[leonardobarreto.com]

OK guys, lets see if you knew this. It is the answer to the purple question in an unexpected way and a good thing to know about the P 25 and P 45


..."What you're seeing is the result of the IR filter mounted on the sensor. Digital backs have a tendancy to see too much IR light. The result is that objects that should be black often record with a purple cast to them. Camera manufacturers combat this with an IR filter which can make it difficult to record deep purple colors.

With the P25 Phase chose on the side of clean blacks, but lost some purple sensitivity.

My P45 has better purple rendition (weaker IR filter), but I often run into blacks which turn purple. I carry an over the lens IR filter for those situations. I like this compromise better than the one utilized in the P25/H25.

Phase does sell an optional IR filter which has weaker IR blocking. You could contact your dealer and have this installed.

You can do the same ICC profiling with Phase that you can do with Leaf. Leaf just has a button in Leaf Capture 10 which start up the profiling program instead of you having to drag you cursor all the way to the dock to do it. The program is Gretags Profile Maker Photostudio 5. It is about $2500.00 plus the $300.00 chart. It will not correct this purple problem you are having, because the purple light is simply not reaching the sensor in the first place.

Your best solution is to upgrade to a P45

Here is what the P45 does with purple fabric (look at the fabric towards the right):
http://www.ericstaudenmaier.com/IR_P45/pages/P45-No486.htm

Here is the H25 version which turns the purple blue:

http://www.ericstaudenmaier.com/IR_P45/pages/H25-No486.htm...."

[Asher Kelman]

Leonardo, this is the identical issue as that which sent earthquake shockwaves through the Leica affecionados who had spent up $4500 to $10,000 on camera and lens combinations to find purple clothes. Disaster for wedding photography, unless like Seain Reid you work a lot in B&W!

The clever profiling of the camera can deal with this, but best is the IR filter when needed.

Asher

[leonardobarreto.com]

Exactly, the model I have has the full filter and the new models are coming with a half -- to say something --. As long as one knows how the camera works is fine, for example, I think I shoot WITH UV filter on, in my case I can remove it to see if the magenta increases or not. That is an easy TO DO test to run alongside the next shoot.

Of course no one explains this when you get the camera.

I think that on the ZD you can easily remove the filter and put it back.

[leonardobarreto.com]

I forgot to mention that this info I got from Eric Staud -- based in Los Angeles -- http://www.ericstaudenmaier.com/

[Asher Kelman]

Exactly, the model I have has the full filter and the new models are coming with a half -- to say something --. As long as one knows how the camera works is fine, for example, I think I shoot WITH UV filter on, in my case I can remove it to see if the magenta increases or not. That is an easy TO DO test to run alongside the next shoot.

Of course no one explains this when you get the camera.

I think that on the ZD you can easily remove the filter and put it back.

I think you mean IR filter!

Asher

[Andrew Rodney]

Or its just as likely to be camera metamerism! Pretty common problem.

[leonardobarreto.com]

Or its just as likely to be camera metamerism! Pretty common problem.

Sorry, but I have to ask: What is camera metamerism?, wait, this is what Wikipedia states:

Metamerism is the situation where two color samples with different spectral power distributions appear to be the same color when viewed side by side. A spectral power distribution describes the proportion of total light emitted, transmitted or reflected by a color sample at every visible wavelength; it precisely defines the light from any physical stimulus. However, the human eye contains only three color receptors (cones), which means all colors are reduced to three sensory quantities, called the tristimulus values. Metamerism occurs because each type of cone responds to the cumulative energy from a broad range of wavelengths, so that different combinations of light across all wavelengths can produce an equivalent receptor response and the same tristimulus values or color sensation. Two spectrally different color samples that visually match are metamers.

there is more here http://www2.cmp.uea.ac.uk/Research/compvis/Metamerism/Metamerism.htm

... could be ...

interesting, thanks

[Andrew Rodney]

Both scanners and cameras can exhibit metamerism or to put it a better way, metameric failure.

Metamerism is also a useful phenomena. Without it, we couldn't get two dissimilar devices or spectral properties to appear to match.

[Asher Kelman]

There's a guy who has a software that uses two-color printing to simulate full color! Wonder whether that is the same phenomenon being exploited?

Asher