Mounting fluid for LF B&W scanning?

[sanking]

Does anyone know of any test comparisions that may have been made between large format B&W negatives scanned on flatbed scanners in the following ways.

1. Emulsion side down on glass.

2. Any side down on glass with mounting fluid.

I plan to do some tests of this type soon and would like to review any literature that may be out there on this subject.

[John Berry ( Roadkill )]

I recently bought an epson 4990. I also use the full version of silverfast. All 8x10 negs were done emulsion side down. I did test with 4x5 in the holder and found scans were more apo, if you will emulsion up. This was done on fp-4 scanned in RGB. I prefer to scan in RGB and use channel mixer to adjut for the tone range that pleases me. I am also interested in trying wet scans.

[Ralph Barker]

I haven't seen any test comparisons, Sandy, but my experience with the older Epson 3200, and the even older Epson Expression 800 Pro, prompts me to scan emulsion down (contrary to the Epson instructions for those scanners). My emulsion-down scans are much sharper. I then flip the image in Photoshop. I haven't tried any of the mounting fluid options, however, so I'd be interested in your test results.

I suspect your results may also be influenced by manufacturing variations between individual scanners, though. So, you might want to ask each of the manufacturers to send you 100 or so random samples for testing. After your testing is complete, these could be distributed to "worthy causes" among the LF community. ;-)

[Ted Harris]

Sandy, I don't recall what sort of flatbed you are using but remember that if it is one of the Microtek 'dual bed' models you need to test emulsion side up as the optics are above the glassless carrier or glass tray.

[Walter Foscari]

I've recently got the wet mounting kit for my Epson 3200 flatbed from:

http://www3.sympatico.ca/gluemax/ScanMax/scanmaxbrochure6.pdf

Based on the totally unscientific tests I've done so far with 4x5 FP4+ I'm not sure it's worth the trouble. The theory behind it sound plausible (flatter negatives, increased contrast..) but in reality I was hard pressed in noticing any improvement. Perhaps those gains are real but are compromised by the other elements in a system of this level (lens quality, etc.)? After trying different combinations I've settled on scanning emulsion side down with the back wet mounted on glass, this seemed to give me slightly better contrast.

There's a yahoo group dedicated to wet mounting on flatbeds:

http://groups.yahoo.com/group/SCANMAX

Walter

[sanking]

Ted,

I am working at this time with two flatbed scanners, an Espon 4870 which I use for scanning 5X7 negatives emulsion side down, and a Microtek 9800XL, which I also use for scanning emulsion side down, primarily ULF negatives. From previous tests I learned that both of these scanners give the best focus when the negative is placed at slightly more than 1.5 mm above the plane of the glass. What I have done is place a second piece of glass, 2/32" thick and cut to the interior frame of each scanner, over the scanner glass. This allows me to scan emulsion side down with both scanners at the plane of best focus. I initially was concerned that the second piece of glasss would degrade the scan but after some testing I am convinced that overall I get better scans this way.

What I am basically interested in finding out is if the certain advantages that one gets with fluid mounting with 35mm and medium format is worth the extra effort with large sheet film. Some years ago i had ten 12X20" negatives professionally drum scanned, oil mounted and everythin, at 600 dpi. But when I compare the results of the drum scans with my own scans of the negatives on the Epson 836XL at 800 dpi, I found little if any superiority in the drum scan.

[Michael Mutmansky]

Sandy,

This does not suprise me. The common logic in the high end scanning world is that if you are not scanning over 100oppi, then you will not see much if any benefit to wet mounting.

I don't know if this is the real point of departure, but what is expressed in this attitude is the fact that as the sample size gets larger, the improvement that is possible through wet mounting become part of the noise. If, however, you were to attempt a scan a 4000ppi (with a scanner that could actually deliver 4000ppi), the differences will be more apparent.

I generally scan 8x10's at 1000ppi and I dry mount them to the drum, because at that resolution, I was not seeing the benefits of the added effort required to wet mount. However, for smaller film sizes, I always wet mount, as the sampling gets much higher.

---Michael

[sanking]

Michael,

I would infer from your comments that there is little or nothing to be gained by wet mounting my ULF negatives, which I scan on the Microtek 9800XL at 1200 dpi, but that there might be some improvment in performance by wet mounting my 5X7 negatives, which I scan at 1800 dpi on the Epson 4870.

In prinitng, I would not be doing more than 2X-3X with the ULF negativs, and no more than 4X with the 5X7 negatives.

[Michael Mutmansky]

Sandy,

Not to say that there will be NO benefit (because if I did say that, someone would prove that to be wrong), but I suspect that for 2x-3x enlargement (720ppi to 1080ppi on the original) I suspect that the benefits would not be worth the (substantial) extra effort.

Additionally, what resolution capabilities can the 9800XL actually deliver? I know that it is a 1600ppi scanner, but have you tested what it can actually resolve? Even if you are scanning at 1200 ppi, it may only resolve 800 or so, which will make the need for wet mounting even less important. Actualy, I'd love to see some resolution and dmax tests for that scanner, if you have them. I'll be trying out the new 1000XL soon, and I'd like to see what the older one could deliver as a baseline for the newer one.

I've done some comparisons with 8x10 at 1000ppi, and didn't see the benefit, because you have to deal with bubbles, etc on big film, and it's harder to get a perfect oil layer the larger you go. Plus, I imagine it's a mess on a flatbed. It's not too bad on a drum.

The results will be similar regardless of the film size, so you could try wet mounting the smaller negatives and then do some comparison tests. If you can see it at 1000ppi, and the difference is worth it to you then go ahead. Ultimately, my threshold is at about the 1000ppi level on the drum scanner.

---Michael

[sanking]

Michael,

I would be happy to give you information on Dmax and resolution tests from the 9800XL but I am at something of a loss as to what test target to use. I have a Stouffer target, but as you mention, the Stouffer has maximum resolution of 20 lppm. The 9800XL is certainly capable of 20 lppm, and more, but how much more I don't know because I don't have a standard target to test beyond 20 lppm. I do have some negatives made of the Air Force resolution chart with a Fuji 6X9 with the 90mm Foujinon EBC lens that shows resolution to about 80 lppm on Plus-X pan film and I was thinking of using these negatives for my own personal tests. However, although this information would be very useful to me in comparing my own scanners it would be rather useless for comparing results with other persons.