None of that makes any sense. The dmax of the scanner allows for the maximum penetration of the light to show the shadow areas the best. Lowering the light to create a different exposure and combining them is not going to increase what you see in the shadows any more than exposing two camera shots at different exposures and combining them afterwards. While it's true that a camera can combine different exposures that have a huge amount of stops from white to black so you can see all the stops in a single photo result, that isn't the case with a negative. All those stops were removed and combined into 5 stops for slide film and maybe 7 stops in negative film when the film was prcessed. A flat bed scanner whether CCD's or CMOS captures all those stops in a single scan.
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That's true if you don't understand the physics of the process (there is a lot that is not straight forward). The light source is not varied, it is not needed to change the exposure. The amount of time allowed for the photons to land on the CCD is changed, in a very similar if not exactly the same way that your camera phone varies the exposure time.
Last edited by Ted Baker; 21-Mar-2018 at 11:03.
Hello Alan,
It is true that a CCD scanner can capture all those stops in a single pass scan, but the question is with what quality !
in fact it can capture any amount of stops, with the proper signal amplification, but we also need to control signal to noise ratio, and we need a wide range were signal has information.
CCD (and CMOS) sensor technology has only improved, but PMTs have anyway a clear advantage. See "What is this Drum Scanner against which all other scanners compare themselves?" section in http://www.kenrockwell.com/tech/scantek.htm
Then it is a fact that Multi-Exposure improves the result when challenging DR is in a transprency or negative:
http://www.silverfast.com/highlights...posure/en.html
Other than scanner applications also have similar problems, it is interesting to see the Arri Alex solution http://www.arri.com/camera/alexa_min...a_mini_sensor/
regards,
Pere
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
I would not expect to see any difference at all. A scanner should not have any difficulty with the shadow areas of a negative, for a negative it is the highlight areas that are more difficult and a colour neg even more so where accuracy or quantization starts to become a problem. Even then a bit of noise in the highlights is not a huge problem, it may be even beneficial... (Noise or grain can in fact compensate for lack of bit depth, for example you can make very good black and white photo with just 2 bits...)
The examples (negatives only) I tested it was only really noticeable with very dense colour negatives, and a single scan using the correct exposure gave the best result.
It is important to understand that a transparency, negatives and digital all have strengths and weaknesses, and the requirements for each are a indeed different.
IMHO a colour negative is the most demanding and difficult to scan even though it has smallest density range, assuming your goal is to reproduce with some fidelity the same result as traditional optical RA-4 colour paper print.
The greatest chance for seeing a difference would be in the most dense part of the film. With BW, that would be in the highlights. And I agree with Ted that unless your scanning under-exposed Velvia you don't need to be able to scan through a density greater than, say, 3, with standard BW negatives being much lower than that. Mine usually have a max density of about 1.5, counting film base plus fog.
“You often feel tired, not because you've done too much, but because you've done too little of what sparks a light in you.”
― Alexander Den Heijer, Nothing You Don't Already Know
Here is an example of a 1.79GB file processed in Camera Raw and PS. Scanned on Epson V850 at 4000dpi, AA turned off, 16 passes and multi-exposure.
try with velvia deep shadows at 3.0D+ or with glare texture in extreme highlights of negative film, you'll see an awesome improvement.
a common shot does not require multiexposure, a challenging one may require a drum for an optimal result
it is when a drum is necessary when multiexposure starts being useful
Steven, The color is way off if that image is meant to look natural. The shadows are all clipped, and there's way too much blue. Take a look at the histogram. The blue channel is definitely funky. Look at the bark of the birches. It's blue not white.
“You often feel tired, not because you've done too much, but because you've done too little of what sparks a light in you.”
― Alexander Den Heijer, Nothing You Don't Already Know
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