Digitizing negative film, how to convert to positive?

[koraks]

I did hope that the dichroic color head will allow me to get rid of the orange cast of the negatives. So I will only need to do a simple inverse of the image captured by the digital camera to obtain a reasonable positive image.

This will work to an extent, although the expectation that simple inversion will yield acceptable results may be a bit too optimistic. In practice, you need at least an S-curve adjustment to get a presentable image, and even if you filter out the orange mask, you generally have to match the gradients of the different color channels. So this means you have at least two sets of curve adjustments you still have to make to get something that resembles reality.

Thanks again for confirming that it is a right thinking of using a dichroic head light source as the first step to scan negatives using a digital cam.

The implication of what I said earlier is that it's not necessarily more or less right than using an unfiltered white light source.

 

[mtjade2007]

I have not done, not even once, scanning my negative with my Sony A7 but have done it plenty of times with a Minolta MF film scanner. I found it always necessary to make adjustment with the curve tool of Photoshop to optimize at least image density and contrast. A lot of times adjustment on each color channel also helped. All these adjustment are often simple and took less than a minute. I think this is due to film scanners remove the orange mask by default for us in the first place. Scanning negatives with a digital camera will need to deal with the orange mask plus all other adjustments needed to be done with film scanner images.

What I hope to confirm is the dichroic color head light source can help removing the orange mask too when scanning the film with a digital camera. Well, figuring out the filter set (just M and Y filtration) of the color head will not be trivial to begin with though. But since it is separated out of the post adjustment by photoshop it should make it less complicated.

I don't understand why it is not different from using a unfiltered light source. Does this mean there is no advantage at all using a dichroic color head light source? The slide copy machine uses a flash light by the way.

 

[reddesert]

When someone does wet color printing, it is the RA4 paper that is designed to deal with the orange mask (more correctly I think the orange mask and the printing process were designed to be compatible). The color head is a convenient way of adjusting the color balance, but it doesn't have a single "minus orange" setting that takes out the mask. Here's a post from Photo Engineer with an overview: https://www.photrio.com/forum/threa...sk-mathematically-c41-ra4.163267/post-2126499

When you scan C-41 negatives with a film scanner, the scanner software has some method of dealing with the orange mask and inverting the colors. What everyone is doing with their inversion methods is trying to replicate that somehow.

 

[koraks]

What I hope to confirm is the dichroic color head light source can help removing the orange mask too when scanning the film with a digital camera.

Does this mean there is no advantage at all using a dichroic color head light source?

You can use filtration to make the dmin of the film appear white on your digital camera capture, but compensating for the mask with plain curves is straightforward just as well (and probably quicker than finding the right filter settings). As said, the main argument for doing this in the light source is about signal quality, not so much ease of inversion - which in the end really doesn't make that much of a difference.

 

[MattKing]

You can use filtration to make the dmin of the film appear white on your digital camera capture, but compensating for the mask with plain curves is straightforward just as well (and probably quicker than finding the right filter settings). As said, the main argument for doing this in the light source is about signal quality, not so much ease of inversion - which in the end really doesn't make that much of a difference.

In addition to the signal quality advantage - good continuous spectrum light source designed with colour quality in mind - the slide copying mechanism will itself provide an advantage - those tend to be designed to permit quick throughput with excellent quality imaging.

 

[koraks]

the slide copying mechanism will itself provide an advantage

Yes, the mechanical setup as such looks quite convenient!