Camera Calibration for Scanning

[silvergelatin]

Has anyone used a Calibrite target plus software to generate a camera profile shot on a specific film emulsion? How well did it work out? I just started scanning with an RGB Scanlight and Ektar colors are tricky to balance due to the increased saturation from the light. Would love to make an Ektar-specific profile.

 

[koraks]

Just set the white balance manually on the camera to whatever approximates a decent balance, and then note the settings for both the light source and your camera settings (exposure + white balance). Then use those exact same settings every time.

You could photograph a target like the Calibrite and then balance the colors as well as you can in post; I personally don't think it's worthwhile to use software for this, but you could. If so, you could look into ArgyllCMS, which probably supports the Calibrite targets out of the box. Personally I'd just make a manual curve and use that as a starting point.

Note that you'll run into inconsistencies anyway unless you always shoot with the exact same exposure under the exact same lighting conditions. In reality you're likely working with a variety of conditions as well as normal variations in exposure, so the color balance will always be a little (or a lot) different. The standard curve you could construct as described above can still act as a starting point, but I bet you're going to adjust the balance nonetheless.

All of this assumes your C41 processing is dead-on consistent. If you're serious about the calibration thing, you're upping the ante on the whole imaging chain. I personally don't think this is worthwhile in practice; if you need this kind of consistency then it's more practical to shoot digital.

Keep in mind you're not calibrating 'the camera' - you're calibrating the entire end-to-end imaging workflow. That's a lot of factors to control.

 

[silvergelatin]

Just set the white balance manually on the camera to whatever approximates a decent balance, and then note the settings for both the light source and your camera settings (exposure + white balance). Then use those exact same settings every time.

You could photograph a target like the Calibrite and then balance the colors as well as you can in post; I personally don't think it's worthwhile to use software for this, but you could. If so, you could look into ArgyllCMS, which probably supports the Calibrite targets out of the box. Personally I'd just make a manual curve and use that as a starting point.

Note that you'll run into inconsistencies anyway unless you always shoot with the exact same exposure under the exact same lighting conditions. In reality you're likely working with a variety of conditions as well as normal variations in exposure, so the color balance will always be a little (or a lot) different. The standard curve you could construct as described above can still act as a starting point, but I bet you're going to adjust the balance nonetheless.

All of this assumes your C41 processing is dead-on consistent. If you're serious about the calibration thing, you're upping the ante on the whole imaging chain. I personally don't think this is worthwhile in practice; if you need this kind of consistency then it's more practical to shoot digital.

Keep in mind you're not calibrating 'the camera' - you're calibrating the entire end-to-end imaging workflow. That's a lot of factors to control.

I’m just trying to wrestle Ektar into something a little more consistent and manageable. The results are great, especially when the neutrals snap into place, but getting there can take some work. Honestly, NLP handles it well, even with the RGB light, but I was trying to create a manual alternative so I can see what is being done to the image.

I read about a simple method where you can use a color checker to feed small corrections into the Channel Mixer and save those as a preset. This is less extreme than a full profile and could be useful.

 

[koraks]

IME Ektar doesn't balance differently from any other CN film. I just do it manually the way I always do; seems to work OK.

If you want to make things easier, it can help to shoot a grey card in neutral light on every roll and then use that as a baseline.

 

[silvergelatin]

IME Ektar doesn't balance differently from any other CN film. I just do it manually the way I always do; seems to work OK.

If you want to make things easier, it can help to shoot a grey card in neutral light on every roll and then use that as a baseline.

I never had a problem before - just getting used to the Scanlight, and the extra saturation makes everything a little more sensitive. I just scanned in seven more new rolls with some different settings, and it worked much better than the difficult images I was testing it on initially.

 

[koraks]

Ah yes, I can imagine the lack of crosstalk due to pure RGB capture boosts the already saturated nature of Ektar, making balancing a bit more fidgety. But by the sounds of it, you've got this sorted; just a matter of a little more practice I'd say. Honestly I think just continuing as you've been doing it is likely more productive than aiming for an actual calibrated workflow, which probably defeats the purpose.