Color Crossover?

[gnd2]

I've been doing some more printing from color negative and reading stuff online I keep seeing mention of "crossover" but I haven't found any explanation of what it actually is or examples or what it looks like. Any more info out there?

[Mark Sampson]

Generally, it's just ugly. Crossovers were usually seen when trying to print an improperly balanced internegative (that had been made from a color transparency original). Commonly you might find cyan shadows and red highlights (with a dichro head and RA-4 paper it would be impossible to correct one without making the other worse).
So, muddy colors in general. It isn't/wasn't much of a problem with a well-exposed color neg original, and a well-controlled print process. Shooting color neg film under light sources far removed from what it was designed for might bring them on, too.

[Mick Fagan]

C41 colour negative crossover is real, does happen, but maybe not as often as people think.

In general the film will be pretty good most of the time, however colour crossover can happen when the light source is out of the spectrum that the film is designed to work in. If you take an exposure under mixed light, say tungsten, daylight, halogen and add a dash of sodium vapour street lighting coming in the door, you almost definitely have a colour crossover negative.

I know this as I once shot under exactly under those conditions, the resultant negative was able to give a reasonable colour print, but not a brilliant one. At least one of the charastic colour curves crossed over at least one other.

Another way to get colour crossover is to have incorrect processing, usually a very wrong time temperature developing scenario, incorrect replenishment rates of the developer meaning the developer isn't correct and maybe one colour doesn't get full development. The possibilities are endless, but the instance of crossover can sometimes be very subtle. A check using control strips of the film developer is pretty much the only way to ensure it isn't the bath doing the film in.

In the link below, go to the illustration number 18, there you will see three lines, representing the three colours in the negative. Colour crossover occurs when one of those lines crosses over another one, then sometimes reverts back to where it should be. The result is pretty good colour overall, but there will be at least one part of the colour in the print that has either a slight weird look, or is really weird looking. That part of the print cannot be be made colour correct.

https://www.fujifilm.com/products/co..._datasheet.pdf

Mick.

[koraks]

I'll give you some pretty severe examples. As to an explanation: Mick basically gave one when he linked to the Fuji datasheet and the curve sets. Crossover is technically if tracking between the three color channels is no longer in unison; the lines of these curves should remain perfectly parallel in order for color reproduction to remain reliable. A breakdown of this can be caused by several factors, e.g. (but not limited to):
* (severe) mismatch of scene lighting and emulsion; e.g. using a daylight emulsion with tungsten lighting without corrective filters
* aging emulsions; the different layers in the emulsion will age differently, creating crossover problems, which at some point become visible/detectable.
* improper processing; i.e. problems with the chemistry or processing regimen
* mismatch between negative and print materials (see examples below)
* incorrect light source spectrum for exposing RA4 paper

Some very bad examples below; these are negatives shot on Kodak Vision 3 50D motion picture film, which is ECN-2 film and not C41, processed in ECN-2 chemistry, but printed onto RA4 paper. There is an inherent mismatch in this case between negative and print material, which is virtually impossible to overcome. In these examples, the problem is very visible:


Notice different color balance with very blue shadows (lower left corner) and very yellow highlights right-hand side.


Same combination, exhibiting the same problem; blue shadows and yellow highlights - you can see just about where the crossover point is, which in this case is approximately at mid-grey.

Here's another example that is associated with C41 developer chemistry. For this negative I used a homebrew C41 developer and outdated film, printed onto RA4 paper (so no neg/pos material mismatch in this case) - also, the lens used tends to do some odd things to color balance likely contributing to the problem:

Notice the magenta highlights and green shadows; overall filtering of this print is a bit too much towards yellow and magenta to begin with, but the crossover in the negative makes it impossible to get a truthful print and all that can be achieved is an 'artistic rendition' (as such, I think it's OK, but it's not technically a good photo of course).

The examples above are very pronounced in illustrating the effect. Very often, the effect is more subtle and can best be described as 'lack of purity' in some or all hues in a print. If you look critically, there are thousands of examples online of home-developed/scanned/printed color negatives that exhibit crossover problems to a larger or smaller extent. In fact, I would go so far as to say that it's quite rare to come across color negative film or color print scans that are entirely free of any crossover...

[gnd2]

Thanks, that was very helpful! I get it now. I'm finding it challenging to learn how to critically judge color.

[koraks]

Judging color is indeed an art. It takes a bit of an analytical view and an understanding of the basics of color theory, but mostly lots and lots of experience. It also helps to have a 'never satisfied' attitude. Look for the faults, not for what you like in a print. However, be careful - that may take out the fun for some people. It can become a balancing act between striving for the best result and achieving gratification at what you're doing.

[Drew Wiley]

There are several possible types of crossover. Some are deliberately engineered into color neg films to provide pleasing skintones at the expense of crisp distinction of related hues elsewhere in the image. Ektar is prone to cyan crossover in the blue range, which needs to be corrected with filtration at the time of the shot. Then there are cases of old film or old paper developing crossover issues. Back in Cibachrome days, the color of highlight crossover would gradually shift as the thawed paper aged over six months or so, and I'd actually time my specific images to match the bias I wanted, which could be quite lovely if subtly controlled. RA4 paper is much more stable, but does tend to get ugly when crossover is finally involved. It can happen through processing errors. But it needs a trained color eye to correctly discern what's going on, because crossover can also affect the purity of midtone hues and shadow values too. Most inkjet prints I encounter are simply awful in this respect because the practitioners have so little color sensitivity.