I’m following the “VueScan Lock Exposure” advanced guide with C41 color negative film. Scanner is Primefilm XA. Every time I attempt to have NLP or VueScan invert the image, it comes out underexposed.
The steps:
Preview
Crop unexposed part of film
Preview Again
Lock Exposure ON
Preview Again
Save RAW DNG following NLP instructions
Am I supposed to change the individual color gains to overlap each other on the image histogram to the right side (maximum exposure given the unexposed part of the film)?
I don’t see a difference with what lock exposure does.
Could this be due to not setting the scanning exposure correctly?
Which (if any) is the correct-looking scan for C41 uninverted film?
I tried to email Hamrick but he said he could not help with this type of question and that I should “hire a consultant and pay him a few thousand dollars to provide this kind of technical support”. Any help is appreciated!
Hmm, I guess my question would be if the individual colors should overlap each other on the right edge, or should I keep the spacing as it should with only the red touching the right edge?
Vuescan, like SilverFast, is supposed to provide for its own controllable exposure and negative reversal algorithms, so what’s the point of using NLP altogether if you are already using one of those other applications? However, if you are using those applications only to drive the scanner and digitize the negative to produce a raw digital negative, I don’t see the point of locking exposure in the usual case when different photos require different exposure to prevent highlight clipping or under-exposure in any one of them. I would expose each negative such that the image data is all contained within the histogram without climbing the walls on either side, then use NLP for roll analysis on all the digitized, still negative images.
I had Roll Analysis reject to use the images of rolls because their exposure was too different. Therefore, and for camera scanning, individual exposures can disable RA. Whether that is the case with scanner scanned images, I cannot say, but there might be something in here:
Where are you getting step #2? That is not correct.
If you are cropping into just the unexposed part of the film (i.e. only showing the border itself in the crop) this will cause the exposure lock to miscalculate.
You want the entire film frame in view when you lock the exposure.
Alternatively, you can hit “lock exposure” and then manually set the “gain” to 1.0. This will make sure that Vuescan doesn’t alter then gain in between frames (which will cause issues with Roll Analysis).
Where are you getting step #2? That is not correct.
I was following the VueScan Lock Exposure Guide after reading the NLP Guide about locking exposure. After running some tests, I couldn’t see a difference between selecting ONLY the film border or the whole image, as the exposure always chose to lock to around 3.07 gain, just before the red started clipping.
After the negative conversion, I can see black clipping and very little dynamic range in the 3.07 gain version compared to the one set to 1. I think what threw me off is the uninverted image looks extremely pale and not orange whatsoever, I assumed it should look at least a little orange like the film itself and the link to your comment below. I will use gain 1 going forward.
Is my understanding correct in that “Lock Exposure” sets the highest gain possible without clipping? Is the unexposed portion of the film considered pure white? Or is there more going on?
Is the current recommendation to still use “Color Negative” media mode as suggested here? That is giving me a much bigger difference.
The biggest goals during scanning in Vuescan are simply:
Don’t clip any highlights or shadows
Use the same “gain” values for all the scans in your batch (to avoid creating inconsistencies during conversion)
For this, locking to “Gain: 1” is usually sufficient (unless you are seeing clipping in the shadows with Gain:1, in which case you could bump it up a bit).
Rarely, some scanning models (like Nikon Coolscan) actually offer analog gain controller, with independent control of the gain for red, green and blue
In theory, this could improve the data being captured. But the tradeoff is that it could lead to inconsistency during post-processing.
Sorry, I’ve been on vacation, can you help me better understand which of these example scans are the more “correctly exposed” ones based on the histogram? I scanned these DNG examples and inverted them using NLP standard settings with “LAB Standard” tone profile. According to VueScan, the 3.07 gain pushed the histogram right before clipping:
To my untrained eye, Color Neg 3.07 gain seems the most true to life, but the histogram shows extremely low exposure. Could it be that this image wasn’t properly exposed when shooting? This is the first roll I am scanning, so I could misunderstand the guide completely. I’m just trying to not mess it up for future rolls. Thanks.
First, I do think the negative itself could have benefited from a bit more exposure during capture. That’s why having the little bit of extra gain in Vuescan is useful (although you could get by with less than 3.07 if you wanted a little more margin for error).
The reason this is helpful is because the highlights of the scene are in the shadows of the negative. So the extra gain just gives a little more for NLP to work with in displaying accurate highlights (in this case, the blue sky).
The decision between Color Neg and Image mode is a personal decision… In general, you may find that Color Neg mode produces finished results that aren’t quite as “lively” but that may be the result you want. I believe you can lock in the color multipliers for Color Neg if you want to go this route, and that would be important to keep results consistent throughout the role.