VueScan - Lock Exposure best practices

No worries, this isn’t really a problem solving thread anyway. I’m simply curious what other VueScan users are doing for the Lock Exposure step. Cheers

I, too, found that locking exposure against the rebate or the whole frame didn’t really do anything when using Vuescan. When converting in LR WITHOUT NLP (ie - before I started using it), I found that it wasn’t necessary to lock exposure at all. I haven’t had a chance to test between locking and not locking at all.

I will test over the coming weekend. What have you concluded so far as to your workflow? Will you continue locking to the whole frame or not at all or?

It would seem to me that locking exposure against “something” (rebate or otherwise) is like shooting in manual mode.

Actually meant to edit it very slightly, not delete it, so 10 minutes later…

It’s quite a long time since I’ve used Vuescan for film scanning and I didn’t use RAW but wouldn’t it be true to say that if you scan to a RAW ‘.dng’ file then “VueScan reads raw CCD sensor data from scanners and can write this to a raw TIFF file for later reprocessing”, from this page here.

So in that case it’s a question of how you set the exposure from that RAW file and that could be:

  1. From the (slightly clipped) light source with no negative in place as Nate seems to favour.
  2. From the film rebate.
  3. From a cropped sample of the negative itself, and that normally would exclude the rebate)

Once you’ve done that for a particular negative then you have the choice of using that setting across all the negatives on the roll by syncing in Lightroom. If you did that then it would be like using manual camera settings where aperture and shutter speed are fixed across the roll. In any case I’d always use a camera on manual whether or not I chose to change the exposure for certain frames.

If you are saying that you set the crop box to ONLY include the film border, then I think you will find it will not produce a proper exposure. I think some users confuse the exposure feature with the film base color feature in Vuescan, which are two separate things. I’ve seen a separate document (not mine) which recommends cropping in on just the film base to try to determine the color of the film base. But for Negative Lab Pro, when you are locking the exposure in Vuescan, you want to include the the entire film emulsion + film border.

Or, you could also just hit “lock exposure” and then manually set the gain to “1.0” and that should work perfectly fine and shouldn’t impact the quality of your scans. The reason is that the gain being applied here is usually digital gain, meaning there isn’t the same “signal-to-noise” benefit you would see from increasing exposure that you would see in a digital camera workflow.

In digital camera exposure, you are actually changing the amount of light reaching the sensor (for instance, by changing the aperture or the exposure time). In Vuescan, my understanding is that it is generally applying digital gain after the regular scan has run. (Your Coolscan may be an exception to this because I believe Vuescan is able to modify the brightness of the individual RGB lights, but I would need to confirm this). In any case, you definitely do no want to clip data prior to conversion!

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Thanks very much for the info, Nate. Makes sense. I will adjust my workflow going forward based on your recommendations.