https://www.silverfast.com/showdocu/en.html?docu=1178Originally Posted by Steven Ruttenberg
https://web.archive.org/web/20180327...html?docu=1178
hmmm, Steven, even with the basic versĦon you can save the 48bit, but with the V850 you even have the Plus version that includes ME and AAOC...
Let me insist, use the software you want but just learn well your bundled version before.
I am following here, lots of informations... I'm new to scanning large format color and B/W negatives.
But, when I scan wihtout ANY color setting, Epson v850 Pro (and others I've seen in the past) produces a bluish uncontrasted positive...
How do I change it to a "normal colors" image?
There should be some presets to clear the orange support color and so on...
Thank you
Please post an screen shot with your settings.
My theory that the scanner does not decrease or increase the captured exposure is as follows. If it decreases, it would be defeating it's higher dmax setting that allows maximum ability to see through the dark shadows. YOu can't increase it because the manufacturer made the unit to be the brightest it could be so it can get the highest dmax. It's already at the highest brightness strength. Finally, due to the limitations of the film itself (5 and 7 stops for chromes and negatives), the entire range is captured in one scan. There's no point doing a second scan. Finally doing two scans getting the same data does not increase the dMax of the scanner. Multiscan ability to make better scans is just manufacturer's hype.
Flickr Home Page: https://www.flickr.com/photos/alanklein2000/albums
This nonsense get repeated again again, even when examples are given. The scanner CCD DOES NOT have a dmax limit IF YOU increase the exposure time, it is just like any other camera in that respect. The DMAX limit as stated by the manufacturer is using a simple minimum exposure set by the need to not fill the wells of the sensor when the density of the film is 0.
What actually varies is the amount of noise relative to the true signal, the errors at maximum density are quite substantial. By increasing exposure you can reduce that noise a tiny bit.
However there are still other problem to contend with, 1. quality of the image at these low density ranges within the film and 2. metamerism (i.e. color) errors are also increased. (I think this is an area where an optimised sensor works better, and may explain some of the improvements found in higher end equipment)
Put simple these last two factors mean increasing the exposure can improve the S/N ratio, but there are still other problem to contend with.
If your shooting negatives, you are unlikely to get anywhere near these limits btw.
Following are two samples scanned by Ken Lee on his v750, over a piece of BW film with a density of approx 3.1. One is scanned with zero exposure gain the other with a 30% increase.
The image has had all the values increased by a linear amount to give the save grey value, you can see the difference in noise quite easily? If you can't see this difference then don't bother changing the exposure.
This is all completely new to me so pardon my ignorance. What am I looking at in those images? Yes I see a difference between the two but no clue what they mean.
This is a scan of a very dense piece of film (a step from a stoufer wedge), around a density of 3.15 (taken by another member Ken Lee). The exposures of each are different, one is longer than other just like when you change the shutter speed on your camera. (one is 30% longer than the other). A bit like changing from 1/125 of second to 1/90s of a second...
The image is then post processed by very simply giving each a linear increase, such that they both have the same values, a bit like putting pieces of film in an enlarger and adjusting the time from 12 seconds to 10.5 seconds to give the same value. (in my example one was increased 12x and the 10.5x)
So the resultant image should have the same tonal value if you like (about 18% grey), but you can see a difference in the noise.
Hope that makes some sense.
Keep in mind this is towards the limits, i.e. a very dense piece of film, especially for negatives, that is being brought up to middle grey, and these are just improvements that need to be seen in context.
Alan, the linear sensor of a scanner is like the one in a dslr in many senses. In a dslr (when fixed aperture and ISO) you may vary exposure time to have a good capture, and also you can use HDR feature to take two shots and later combining both shots in a single one to deal with an ample dynamic range that surpases the dslr capability.
This is what Silverfast does in a V850 when Multi-Exposure used, it takes 2 scans of the negative, each made with different exposure times. A drum uses a PMT sensor that has way more dynamic range, so it may not need that feature. Also I guess that some expensive flatbeds do not make two passes to obtain two images that are to be combined, but in that case two consecutive exposures of the same row are made before advancing to the following row.
These kind of tricks are common in imaging devices, for example Alexa movie camera uses "DGA", the analog voltage from each pixel feeds two ampliers instead one, working each at different ISO, this extends dynamic range because for the same image acquisition there are also 2 analog to digital converters, so each pixel in a shot is taken at two different ISOs to be later combined in a single reading.
I the case of a cheap V850 the implemented solution is making two passes each with different exposure.
Makes sense now. Thanks
I agree with last couple of posts by Ted and Pere. I have this experience in my scanner as well, V850.
For linear raw output though, I have not found a way to adjust the exposure. I have tried, but I always get same raw output, regardless of setting or software used.
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