Doing color negative inversions manually

[avandesande]

As explained in my earlier, lengthy post, there can be a net information gain by applying analog gain before the signal is fed into the ADC if media are scanned with a density range less than the scanner's dmax.



If this is the case, and it may very well be, then analog gain is indeed used, it seems. One of the ways to amplify the signal on a photo site is to increase exposure time. This logically results in a longer scan time. It also increases noise, but again, the net information gain can outweigh the disadvantage of the noise generated.



This is discussed in a few other threads on camera scanning and the best light sources to use for this. What this doesn't address is the issue of frame-to-frame or roll-to-roll consistency, or that of color balancing. Using a color head doesn't automatically mean the scans come out perfectly balanced. Also, (quasi-)modern Fuji Frontier scanners use an RGB LED array for illumination - is this what you understand to be a 'color head'? Keep in mind that when printing color the old-fashioned way, you still adjust filtration based on the film used and usually for exposure conditions, and you may have to account for deviations in development if that happened to be a little sloppy. There's no auto-magic when using a color head.

It's not a perfect solution but my experience is that the more you mash around with curves in a photo editor the worse an image gets. Using a color head to get you 80% there would be an improvement.

 

[Alan Edward Klein]

Scan flat and open the shadow slider a little if you absolutely need some details. Just don't overdo it. Messing with the scanner's scan speed will not yield much but more frustration with scanning. Keep it simple.

 

[radialMelt]

With regard to the analog gain feature in Vuescan, I'm pretty sure it is only relevant (and applicable) to Nikon Coolscan scanners, which do allow for exposure times of each channel of the LED illumination to be adjusted.

Input Tab | VueScan Manual

www.hamrick.com

 

[koraks]

exposure times of each channel of the LED illumination

I really, really doubt that the illumination has anything to do with this. It sounds like a longer integration time, which is essentially the time you allow for light to hit the sensing element. I doubt the backlight is modulated at all and don't really see the sense in doing so.

 

[koraks]

Using a color head to get you 80% there would be an improvement.

It doesn't work this way. A color head doesn't magically expand the dynamic range of the dye images. The filtration just transposes the curves up or down a bit, andattenuate parts of them. But again, that's another thread.

 

[radialMelt]

I really, really doubt that the illumination has anything to do with this. It sounds like a longer integration time, which is essentially the time you allow for light to hit the sensing element. I doubt the backlight is modulated at all and don't really see the sense in doing so.

Didn't mean to imply that. I said exposure times of each channel of LED illumination, i.e., longer exposure for red channel vs blue channel, etc

Thanks for the video by the way. Educational!

 

[Steven Lee]

@koraks you may also enjoy reading this blog post. (ignore the "with digital camera" part, it's generic) It allows for low/no cost automation of majority of the process, leaving just the final touches to eyeballing.

 

[avandesande]

From what I can tell the Frontier makes adjustments by modulating the light sources, not manipulating digitally. What I am suggesting is you could approximate some of this by using a color head.

 

[koraks]

each channel of LED illumination, i.e., longer exposure for red channel vs blue channel, etc

Are you sure the LED backlight on those scanners is actually RGB? On my unit, it's an array of white LEDs.
Mind you, they could still use a different integration time per channel - which would make perfect sense especially when scanning color negative. But it wouldn't be associated with the backlight.

@koraks you may also enjoy reading this blog post. (ignore the "with digital camera" part, it's generic) It allows for low/no cost automation of majority of the process, leaving just the final touches to eyeballing.

Looks interesting; thanks!

What I am suggesting is you could approximate some of this by using a color head.

I understand the perspective, but it won't make a difference w.r.t. actual color resolution. What the guy says in the youtube video is a haphazard conclusion. That fuji chose to change illumination instead of working on the sensing side to adjust color balance is likely a practical consideration and doesn't make a difference in terms of what's fundamentally possible in terms of getting good color balance, optimal color resolution etc. You can use a color head for scanning. It just won't be better in any way than using any other approach that captures the entire density range for each color channel and then adjusts gamma as necessary. There's no inherent magic to a color head. But, for a final time - that's a matter we have discussed in depth in another thread. Let's leave this tangent; feel free to look up the other thread and rekindle that discussion if you want to pursue it further.

 

[brbo]

With regard to the analog gain feature in Vuescan, I'm pretty sure it is only relevant (and applicable) to Nikon Coolscan scanners, which do allow for exposure times of each channel of the LED illumination to be adjusted.

Some other scanners support this too. Well, at least some Minoltas do...