Color Correction References
I've just started RA-4 printing from C-41 negatives and have been giving some thought to getting the color nailed.
The need for this really hit home when I switched from 160NC to Superia 400 mid-print-session earlier this week.
I really already knew I needed to do something along this line because I enjoy shooting some with a Holga. (She's my first and her name is Helga )
I'm now planning to shoot a frame on each roll with a grey card; actually a black, white, and grey card set I have already.
The other thought I had here was leaving one frame unexposed on 135 or using some of the unexposed leader of 120.
So my questions:
1 - Can any of this be judged during "focusing"? (i.e. Can I see this on the paper in the easel before exposure?)
2 - Is a blank frame valuable say to judge the basic color correction for the roll and find max black or is the "grey card shot" plenty?
3 - Are there other tricks to make this quicker and more accurate?
Mark Barendt, Beaverton, OR
"We do not see things the way they are. We see things the way we are." Anaïs Nin
Look for a Macbeth color checker card to photograph one exposure per roll.
Look for a Kodak Color Print Viewing Filter Kit - this, along with a daylight light source, will give you a pretty accurate way to judge the color balance of your prints (especially if you have the Macbeth color checker printed for a particular film).
Colour checkers, even the little ones meant for digital can be pricey. Scour the web or camera shows etc. for an old color darkroom data guide from Kodak. They include a test swatch page of clour chips opposite the page of grey card stock.
One shot per type of film, per lighting situation is usually enough for me of a such a color swatch.
my real name, imagine that.
Highly unlikely just "by eye", as the color mask on the film and the reversed colors will throw you off. This is possible with a color analyser, but you need to calibrate those to printing results.
Originally Posted by markbarendt
The blank frame will tell you about the film, but the grey card shot will tell you about balancing for the light source used for a given shot. Those aren't the same thing, and the grey card negative is the one to use to judge color balance.
Originally Posted by markbarendt
The print viewing cards already mentioned can be very helpful, but judge by a mid-tone with them, not a bright highlight or deep shadow.
Originally Posted by markbarendt
You might be able to find a used color analyser for printing. These should be pretty cheap these days. They like a known target like a grey card.
If you can't afford an Xrite/Greytag/Macbeth ColorChecker, try paint chips or formica samples from your hardware store. Some paint chips show a nice gray scale, and you can take your grey card in to help find the most neutral. However, the reason that the ColorChecker is so expensive is that the pigments used are not subject to weird color renditions under widely varying lighting conditions (sun, shade, tungsten, fluorescent, flash, etc). Many pigments and dyes shift their appearance radically under different light sources and can throw you off. Whites often have optical brighteners that throw you even further off. So you'll need to see if any cheap substitute actually works as needed.
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The light you view the print under can change how you color balance, as well. There are very expensive light units to use, but Kodak recommends a pair of fluorescent lights with "Cool Deluxe White" bulbs and if you want a mix of daylight and tungsten like a gallery with big windows, add a 75W flood light for every pair of fluorescent bulbs. Make sure you only view the dried print. A wet print will have a different color appearance.
First, about balancing; I find that the experience with color printing will be your best guide! I have not used any special means to balance, just my eyes at the final print, making some test sheets. And I've wrote down starting filtrations for different films & shooting conditions. You can make a table like this:
--------- Tungsten light -- sunlight ... etc.
Film1 ----- xx M xx Y ---- xx M xx Y
Film2 ----- xx M xx Y ---- xx M xx Y
Film3 ----- xx M xx Y ---- xx M xx Y
Now, after two years of occasional printing, maybe a hundred sheets, I can guess the correct filtration very close and make the final correction usually after one test sheet. So, just take your time.
Yes, you can use unexposed frames to balance for the orange mask, but why bother, as you can take an actual picture and do the same balancing and get a picture, not just gray frame.
And remember, the light when shooting matters. If it's cloudy or sunny or if it's taken indoors... The colour temperature differs quite much ranging from 2500K to 9000K. That's a huge difference in balancing (from about 80Y to 190Y on our Fujimoto, plus some magenta tweaking).
Then, about viewing the prints;
There is a very common disinformative belief (initiated by the marketing staff of daylight lamps) that you need a "daylight lamp" to evaluate your prints, but that's 100% bullshit for two reasons:
1) It tells (or it SHOULD tell...) you what the print looks like in daylight-balanced light, but what do you do with that information if the print is not viewed outside in the sunlight? The [i]only[i] correct color temperature for print evaluation is the same type of light source where the final print will be viewed! It may be sunlight, but at home, it's usually 2800...3200 K tungsten, and in galleries it can be 3400K tungsten ---- all very far from "daylight lamps"! Or it may be some combination of sunlight and artificial light.
2) There is NO decent fluorescent "daylight". Fluorescents have no color temperature at all, it's all marketing. The best ones can be quite close but not quite and they are expensive.
SO, when evaluating your prints, try to use the same type of illumination than where viewing the final prints. Probably they will be looked at all kind of color temperatures, so this game has been lost from the beginning and you don't have to stress so much about the color of evaluation light. The eye has incredible tendency to balance automatically.
Combining different types of light is actually quite a good idea. You can even have them in different directions so you can see the effect when moving your print.
Fluorescents do have a sometimes 'spiky' spectral output. But they are referenced to a color temperature (CCT) standard, with a color rendition index (CRI) that ranges up to 100 for perfect visual color rendition. You can get GE Chroma 50 or Philips C50 fluorescent lamps for a typical 4 foot shop light or ceiling fixture. The Chroma 50 has a CRI of about 90 or 91, and the Philips C50 has a CRI of 92 with reference to a 5000K daylight CCT standard. Both of these would meet industry standards for judging color balance by eye, which is what they are designed for. They are also designed by lighting engineers, not marketing divisions.
Originally Posted by hrst
As mentioned earlier, human vision compensates for viewing conditions, but evaluating prints for general use can be done very well under high CRI fluorescents.
Last time I checked, the Philips C50 was under $5 for a 4 ft fluorescent tube at Home Depot in the US, where the OP lives. A shop light and two 92 CRI Philips lamps would be about $20 at Home Depot.
Two items I find useful are the already mentioned color filter viewing kit and the ring-around in the Kodak color Darkroom Dataguide. Lee filters has a good viewing kit available from many of the APUG sponsors. The Dataguide can be found used through Amazon quite easily.
I should add to my post that you need to consider where your photos will be seen. If you only show them at home, look at them under your house lights. I print for exhibition, so I use Kodak's guide to give an average gallery lighting situation. Most galleries have large windows with cool daylight and add spot lights to the artwork. This is what I print for, in general. And I use the color viewing filters because I have one eye that sees cooler than the other. This prevents me from just eye balling the print color.