First scans with Epson V850

[Steven Ruttenberg]

I have plenty of old color negatives, bw negs and slides. So I can practice. Used all kinds of film.

[Alan Klein]

I have just tried the Multiple Exposure mode with 2 black and white negatives using SilverFast AI Studio. I scanned one with ME On and one with ME off and I am finding it difficult to see any real difference in the deep shadows

Like I've been saying, there is none. It's all a lot of hype from the after sales software companies to sell scanner software. You're limited by the scanners dmax. Changing the scan time is like increasing the ISO from base ISO of a digital camera. Sure you might see more. But it will be noisy. You can accomplish the same thing scanning once and increasing the shadow slider (for positive film) in your post processing program. I've never seen anyone ever post a before and after comparison using multiple scans that were ever any better than using the shadow slider on the first normal scan.

[Steven Ruttenberg]

I have plenty of old color negatives, bw negs and slides. So I can practice. Used all kinds of film.

Have you tried it with vuescan?

[Ted Baker]

Like I've been saying, there is none. It's all a lot of hype from the after sales software companies to sell scanner software. You're limited by the scanners dmax. Changing the scan time is like increasing the ISO from base ISO of a digital camera. Sure you might see more. But it will be noisy. You can accomplish the same thing scanning once and increasing the shadow slider (for positive film) in your post processing program. I've never seen anyone ever post a before and after comparison using multiple scans that were ever any better than using the shadow slider on the first normal scan.

Your contradicting yourself

Multi-exposure or changing the exposure time is not an ISO change, it is a exposure time change, thought I AFAIK the recent Epson flatbeds can also change the ISO for the respective channels when scanning colour.

In a recent thread a V750 owned by Ken Lee was sacrificed to show that the DMAX does change with an increased exposure time, in addition those tests showed the response of the CCD is not entirely linear through out the range, and the quantization errors are likely to increase markedly towards Dmax. BTW the whole point of linear scanning is for accuracy and calibration, the final print is absolutely non-linear. For example many of the best drum scanner use a log amp instead of linear scanning, they tackle the problem of accuracy and quantization in a different way.

Of course for many applications none of this matters, but some us are interested in how things work, and making small improvements.

[Pere Casals]

Changing the scan (exposure) time is like increasing the ISO from base ISO of a digital camera.

No! it's like changing the exposure time of the digital camera !

Increasing the ISO it does increase ISO related noise. Increasing exposure time it does not increase noise. It is true that a 20 seconds exposure in a DSLR may add dark current related noise (that can be compensated with a calibration shot), but this only happnes in night shots, not in scanners with linear sensors...

A DSLR shot at ISO 1/125 - ISO 400 has less noise than if 1/250 - ISO 800, does not?