How to correct slides color cast when projecting or developing

[pyr]

Hello,

This is my first post on the forum. Thank you for the great advice found in other posts !

I have recorded digital photos on Kodak E100 using a digital film recorder (CRT) and developed the slides in E6. They look good but have a yellow cast to them.

How can I fix that ?

The files were calibrated on a screen and exported with adobe-rgb profile, so I have assumed that the calibration of the film recorder may be off. I don't think I can go into re-calibrating it so I may make tests with cooler white-balances in the next batch of files, hoping that the film recorder doesn't correct the color temperature automatically internally.

Alternatively, is there a way to modify the slide temperature when processing ?

Now I have recorded 150 slides that have this cast and I wonder if I could use some filter mounted on the projector lens to correct this batch of slides and also in case my future slides also have this very same cast. Do you think that could work ? What kind of filter would you advise me to use ?
I have tried old gel filters and the colors look better but they soften the image too much. So I wonder if glass colour filters could be better ?

Any advice on this would be very welcome. Thank you and kind regards.

 

[MattKing]

Moved to the Hybrid Discussions sub-forum.

 

[wiltw]

Way back in time, there were Kodak Color Compensating Filters and Kodak Color Correction filters...one was an acetate filter, the other was a gelatin filter.
One was put above the negative to color the light illuminating the negative, while the other was put below the lens in the light path to the print paper. I forget which was gelatin...'compensating' or 'correction' filter. gelatin filters are generally considered better than acetate filters when placed in the optical path due to their superior optical quality, providing more precise color filtering and better light transmission. Gelatin filters might require more careful handling due to their delicate nature; acetate filters are often used in situations where cost is a primary concern or where high precision is not necessary.

You could get some filters (small sheets) and cut small squares of filter material and sandwich it with the color transparency in the slide mount.

There are specific versions of filters meant to alter color balance (make it warmer/colder), or use the general compensating/correction filters if there is a color cast to correct, not merely color balance.

 

[pyr]

Thank you wiltw, those filters are still manufactured apparently : https://www.kodak.com/en/motion/page/wratten-2-filters/

Do you think I could insert them in front of the projectors lens to avoid having to re-mount each slide ?

 

[cmacd123]

Thank you wiltw, those filters are still manufactured apparently : https://www.kodak.com/en/motion/page/wratten-2-filters/

Do you think I could insert them in front of the projectors lens to avoid having to re-mount each slide ?

if all your slides are off by the same amount, and you are not planning to use any Real Slides.

 

[wiltw]

Thank you wiltw, those filters are still manufactured apparently : https://www.kodak.com/en/motion/page/wratten-2-filters/

Do you think I could insert them in front of the projectors lens to avoid having to re-mount each slide ?

If you use gelatin filters, not the acetates, they can go in the light path between lens and screen, with little impact on image quality. And it could be OK if you are simply correcting color balance for a series of shots taken indoors with daylight film. Correction of color shifts seen in aging slides is an individual shot kind of adjustment.

 

[pyr]

Ok I understand

Do you know the difference between Kodak colour compensating filters, which seem to be hard to find and expensive in France and "regular" gel filters (Lee CTB filters for instance), which seem to be easier to find ..?

LEE Filters Blue | 201 Blue Gel Filter Specifications

Read the technical specification for LEE’s 201 blue gel filter that converts tungsten (3200K) to photographic daylight (5700K).

leefilters.com

I have made tests with Lee CTB and they soften the image, which now lacks micro-contrast.

Would glass filters be more transparent and leave the image more punchy ? do they exist ?

Thank you

 

[mshchem]

Welcome to Photrio!!

 

[mshchem]

This is not a common practice. (Filters on projector lens)

You can try any colored material in front of the projection lens, but it will darken the image.

This is best resolved when you are recording on the film

 

[Don_ih]

Was the colour cast due to using a daylight balanced film in a device that outputs artificial light, or is there a setting for daylight film? Could you put a filter between the camera lens and the crt in the recorder?

 

[pyr]

I may try putting a filter in the recorder itself though I am not sure I can open it and do that safely.

In the software (raster), i selected E100 film that I used to record mainly photos shot outdoors. I have not seen a specific setting for indoor/outdoor but I will look into that. The recorder is a lasergraphics personal LFR.

 

[koraks]

In case no official calibration procedure can be found, you could try manually adding a compensation curve to your images before outputting to the recorder. You could approximate an adjustment by creating a chart with calibration patches and then determining an adjustment curve that compensates for the deviations you see. Some kind of color transmission densitometer might help, although 'eyeballing' the result may be sufficient for your purposes. It would help if you do the E6 processing yourself to keep iteration time short.

 

[Ian C]

An easy way to determine the required correction is with the use of a set of Kodak Viewing Filters. This is a common tool used in color printing in a home darkroom.

You’d view through each of three different densities of the color chosen and use the best correction to determine the correction that gives you the most accurate color. These filters are acetate and are not optically corrected for actual printing or projection.

Then, with the correction you determine, order a correction filter of the proper value and install it on the front of the projection lens.

For example, if you determine that a blue 10 CC (10 color correction units) is the best filter, you can order a CC10B filter. That should come close to giving you the desired color correction.

Here is the instructions for using the Kodak Color Viewing Filter Kit.

“Kodak Color Print Viewing Filter Kit​

How to Use

First make a test print. Adjust the exposure to produce the correct density of the middle tones. Then judge the test print under the same type lighting conditions to be used to display the print. View the print through the filter(s) that makes it look best. If the color balance is on the warm side, use the green, cyan, or blue filters to view the print. If the color balance is on the cool side, use the magenta, red, or yellow filters. At times you will find that a combination of a warm and a cool color makes the test print look best.

Prints from Color Negatives (white side of viewing filter cards)

Judge the lighter middle tones in the print by holding the filter several feet away from the print and light source. Quickly flick the filter in and out of your line of vision to observe the color correction the filter makes. Viewing filters will tinge the highlights excessively and the shadows insufficiently; therefore, disregard these tonal extremities and judge the effect primarily on the basis of the middle tones. You have a choice of three density levels for each filter: 10, 20, and 40. Once you have determined the filter or filters that make the test print look best, adjust the filter pack in the enlarger by adding or subtracting the filters that are specified on the card below the selected viewing filters.

Exposure Adjustment for Filters

Whenever the filter is changed, allowance should be made for the change in exposure introduced by (1) the change in filtering action, and (2) the change, if any, in the number of filter surfaces. Otherwise, the density of the corrected print will differ from that of the test print.

If the pack is changed, use of the appropriate filter factor in the following table is convenient. Filter factors are not usually required for dichroic filters.”


These viewing filters are no longer made but can be found in good pre-owned condition on eBay and elsewhere.

https://www.ebay.com/sch/i.html?_nk...sacat=0&_from=R40&_trksid=p4432023.m570.l1311

Unfortunately, Kodak gelatin CC filters have become expensive in recent years.

https://www.bhphotovideo.com/c/product/817538-REG/Kodak_8577959_3_x_3_CC10.html

Lee polyester filters are more economical

https://www.bhphotovideo.com/c/product/102511-REG/LEE_Filters_B10_4x4_Blue_CC10B.html

Both are intended for use over a camera lens. This is best done as the image is recorded onto the film if possible.

 

[wiltw]

Ok I understand

Do you know the difference between Kodak colour compensating filters, which seem to be hard to find and expensive in France and "regular" gel filters (Lee CTB filters for instance), which seem to be easier to find ..?

LEE Filters Blue | 201 Blue Gel Filter Specifications

Read the technical specification for LEE’s 201 blue gel filter that converts tungsten (3200K) to photographic daylight (5700K).

leefilters.com

I have made tests with Lee CTB and they soften the image, which now lacks micro-contrast.

Would glass filters be more transparent and leave the image more punchy ? do they exist ?

Thank you

The Kodak Color Compensating filters, "WRATTEN Gelatin Filters"...they can go in the optical path between the lens and the projection screen. Lee filters are also gel filters.

The Kodak Color Compensating filters were originally intended for fine-tuning color balance, filters with somewhat low intensity, what one might use while printing color negs with an enlarger that does not have a color head or filter drawer. They might be used to correct dye fade due to age in a color transparency.
The Lee lighting filters are generally somewhat intense, for shifting incandescent light to daylight color balance, for example. Their camera filters are mostly different kinds of ND anc CPL.

 

[pyr]

Thank you all for the answers.

Although I may try fine-tuning the calibration of my pictures for this particular recorder in the future, I have found that adding Lee magenta gels in the path between the bulb and the slide of the projector solves the problem to my liking. I may try kodak gels and kits later, but they are expensive and I am not sure I would see any benefit when compared to Lee gels which are easily available to me.