Bit depth = levels of gradient?

Started 2 months ago | Discussions thread
OP filmrescue Contributing Member • Posts: 802
Re: Bit depth = levels of gradient?

John Sheehy wrote:

filmrescue wrote:

Thanks for your thoughtful answer. I do have negatives that are captured with a DSLR that maybe occupy 5% of the tonal range where I end up with what I thought would be best described as posterization or banding that will disappear after I scanned them with a 16 bit actual film scanner.

What file format? JPEG tends to create posterization to make more compressible images. RAW captures are rarely posterized except in near-blacks in a small number of cameras, mostly the first Exmor sensors that had too little noise at base ISO for 12 bits.

I need to go back and look at what's going on in ACR but I generally only see the jpegs after the work is done (by someone else who works here) The original files are 12 bit NEFs and are opened as 16 bit files and saved as jpegs. The banding is fairly uncommon and only manifests itself if the conditions are right. Conditions being right meaning that the image isn't overwhelmed by actual distressed film issues so that what appears to be a digital artifact comes through in the form of banding. Perhaps the issue I'm concerned about is only showing up in the save to JPEG.

So you're saying that's not coming from a lack of band width but from noise?

Not posterization. Posterization is a lack of noise before quantization.

Maybe I have my terminology wrong. I thought "posterization" and "banding" were interchangable?

Yes, of course as you bring up contrast you bring up all sorts of other issues, grain, dust, scratches, mottling...all minor imperfections become major issues.

The less artifacts you get in the capture, the less you'll see when you boost the contrast. You could consider using the principals of astrophotography with multiple exposure to minimize any artifacts that aren't already in the film.

I had considered trying that at some point but there's only so much that can be done at the price point we charge...in the end though you're onto something about noise albeit in my case the biggest issue is analogue noise in the form of film grain overwhelming the image.
The original point of this post was I'm trying to make a decision on a new capture camera for when we photograph these negatives with a camera. A camera because so many of them are extremely low contrast to the point, you can't find the frames with a preview scan on an actual film scanner and often the negatives are so dense, an actual film scanner can't scan through them.  For context, my company specializes in the processing of lost and found expired film...that's why we deal with so many terrible negatives.
Any thoughts on what would be the actual best thing to do our captures with. in contention right now is ...
A Nikon D850 - the most affordable option

A Microbox Book2net book scanning camera - 16 bit and multispectral but not sure if the multispectral part of that will help us or not. We have test film with them now.

A Fuji GFX 100

A Phase One ixg with their DT film scanning set up - this is likely more of a pipe dream because it's hardly affordable for us but if it does something amazing we'd probably find a way.
Most of these were chosen because they're 16 bit...You don't think we need that? I'd love your thoughts on any of these as a film capture device. You seem well informed.

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