I scan MF 120 6x7 on my V600 using 2400 ppi and 48 bit. An image file is about 200mb. Scanning at 6400 would give me a file 7x as large about 1.4gb. At 4800 the file is 4 times as large at about 800gb which I think is the limit for Lightroom. Does anyone recommend something over 2400 which I had heard back when was the most you could get out of the V600? Advice?
Yes.....higher resolution increases file size....no surprise there. File size won't be close to 800 GB though.....maybe you mean 800 MB?
Also, let's say I try different ppi's. What do you look for when comparing to see when there's no more resolution from the scanner? Advice?
I don't know the V600 specifically....but the first thing would be to find the highest *optical* (or native) resolution your scanner is capable of. On my V750, that seems to be 6400. So start at the highest optical resolution and scan in 1/2 increments from there.....6400, 3200, 1600, 800, etc. Don't bother with in between resolutions like 4800 or 2400 as they are likely interpolated.
For testing the detail rendering of your scanner, first off, you must make sure that it's focused properly. If you're using a film holder, you might have to play with "shimming" the holder to get optimum focus. Also try scanning the film emulsion up and down and see if it's makes a difference. On the 4x5 sheet film I was testing, it made a HUGE difference. When testing focus, I would suggest using the highest resolution and scanning just a small section in the center.
After you've got that worked out, time to run the scanning tests at the various resolutions. When picking a film frame or area to scan, I would recommend scanning an area of relatively LOW contrast like fabric texture or something. Scanning areas of high contrast will likely cause "flare" (not sure if that's the correct term) where light coming through clear areas of the film bleed into the denser areas. Scanning a dense area of low contrast detail will give you the best chance of seeing what your scanner can resolve. Oh, and any sharpening in your scanner software must absolutely be disabled. You don't want to get fooled into evaluating *acutance* instead of real detail.
When evaluating the scans themselves, the first thing I do is up-sample all the scans to something like 9600ppi using "Bicubic: Automatic" in PS. After upsampling, use the Window -> Arrange menu in Photoshop and tile them....I use "Tile All Horizontally" to use the full width of my screen and I also hit the TAB key to get rid of tool palettes and such. After tiling them all, click on one of the windows and set the view to either 100% or 200% depending on your personal pixel peep level
and then move the image around till you find the area of detail you want to view. Once you have one window set to the detail area and view %, use the Window --> Arrange --> Match all option to get them all to exactly the same area.......let the evaluation begin! I find it helpful to slide my chair back to get a good view....then I start closing windows that obviously have poor(er) detail....probably the first couple lower resolutions. That should open up the remaining windows to view a bigger area of the scan(s). Look at them critically.
After you've done that, you could also down-sample them to, say, 3200 and evaluate them again. Quite often the higher-rez scan will still hold up better to down-sampling than the one scanned directly at 3200.
As an aside, the Dmax might be the bigger issue. On the V600 is 3.4 and on the V700 it's 4.0. So shadow areas will scan better the higher the Dmax. When I scan, there always are huge amount of sharpening that are required either by the scanner or in post if I scan flat.
Quotes of certain Dmax values on consumer flat-bed scanners are largely bullshit....or at least meaningless. They are usually calculated from the the native bit depth of the scanner and not the actual *optical* density it's capable of rendering. I was doing some reading on this recently and the best explanation I read was that the bit depth refers to the *size* of the density container....but it says nothing about whether the scanning optics can actually FILL that container.....like having a sack that can hold a million bucks....but that doesn't mean the sack actually HAS a million bucks in it.
And those Dmax numbers are kind of meaningless in another context. Most B&W and color neg films won't go beyond about 2.00 Dmax (I've measured them)....and the actual Drange is about a stop less than that. So from a density standpoint, you're not going to find many, if any, neg films that go beyond about 6-7 stops of density (nothing to do with scene dynamic range though). It's true that transparency/slide films have a higher Dmax but I can remember back in my drum scanning days that I would typically never see a Dmax (non-exposed area of the film rebate) over about 3.20......but I've heard that Fuji Velvia can go a bit higher. Point is, Dmax specs beyond about 3.4 are pretty useless since you'll rarely find a film, especially negs, that push those limits.....assuming the scanner's optics are up to the task.
Terry
