Are you scanning at the right height

[Joanna Carter]

Hi folks

I have just started to scan a few old 645 negs and came across an interesting problem. The Epson V700 scanner is supposed to be "better" than the 4870 and yet I was getting very soft scans of these 645 negs compared with those I previously got from the 4870.

Now, I know that the V700 has scan height adjustment, so I tried all three available heights, but the best result at the greatest height was still a bit softer than the 4870, so I decided to try adding extra padding in the form of strips of printing paper under the film holder.

Sure enough, I managed to get a sharper scan; so after a bit of trial and error inserting different thicknesses of paper, I finally got to what I considered to be the optimum sharpness. But here comes the interesting bit: I thought my V700 trannie scans were pretty darned good, certainly sharper than the 4870, but when I tried adding extra padding to the film holder's height, I got even sharper scans.

It would be intersting to see if adjusting the scan height on other flatbed scanners also improves results. Anyone want to try?

[DJ]

It's a well known phenomena, there's quite a bit of variance between different models, and even different units of the same model. I've found through trial and error my 4990 to be optimal about .5mm above the glass, some unlucky souls have found that their units have the focal point below the glass and so impossible to achieve!

The V700 and V750 are slightly different from other scanners, in that they have two different "lenses" for want of a better term, which are focused at different heights. The lens the scanner uses depends on which setting you choose for the film type. The main "lens" is the one used for regular reflective scanning, and some film scanning and is focused just above the glass. This lens is used if you scan film and select the "film area guide" option and are laying film directly onto the glass. The other lens is used if you select an option using one of the film holders, and is focussed about 3mm or more above the glass. Some people have reported their sharpest scans by scanning directly on the glass, but here you will have to content with Newton rings etc. Most use the film-holder option.

With such variances between units, it definitely pays dividends to calibrate your own scanner.

[Joanna Carter]

DJ, in your experience, how critical is it that the neg/trannie is completely flat? I have thought of getting some anti-reflective glass, mounting the film so it curves upwards, adjusting the film holder height to account for the emulsion down, and then placing the anti-reflective glass on top of the film to keep it flat. To my mind, the glass shouldn't interfere with the scanning as it is on the lamp side of the film rather than the sensor side.

What do you think... ; and how are you measuring the height so accurately?

[DJ]

If it's not completely flat, you will get slight variances in sharpness. How extreme these are, and if they're even noticeable at all will vary from scan to scan I guess. I've noticed it on some, and not on others, that said, I've not done a great amount of 5x4 scanning. The best scanning method is drum scanning, whereby the film is fluid mounted on a drum, so it has a constant focal distance. Imacon scanners give good results because they actually bend the film in a curve in a thin metal holder, so it's focal distance is constant (which is why they've coined the "virtual drum scan" phrase). However, both those types of scanner are outrageously expensive

The problem I had with my 4990 and standard holders was that my scans were taking so long, the lamp heat was heating up the film, softening the gelatin and causing the 5x4 to bow in the film holder, allowing it to touch the scanner glass, causing Newton rings. It's because of this I investigated the wet-mounting methods to ensure the film was totally flat. The wet mounting approach was more successful, however it's a huge pain compared with using a film holder.

The method you suggest is also tried and tested, and apparently works well, although the standard holders have a poor reputation. There's a guy called Doug Fisher who's developed and sells medium format holders for the Epson and other scanners to do just this, with the anti-newton glass, they apparently work well but I have no personal experience. They also have removeable "frames" to allow scanning 6x17 formats etc. The address is http://www.betterscanning.com/. He has yet to produce a 5x4 film holder however although the page says it's in development. I think we should put lots of pressure onto him

If you're going to put the anti-reflective glass above the film on the lamp side, I agree it shouldn't affect the scan, but I would advocate re-profiling with this glass in place, as the slightly opaque nature of the glass may affect the levels in the scan.

I worked out the distance on my scanner by creating a set of shims. I bought A3 sheets of black styrene from a model-shop supplier in various thicknesses ( 0.5mm, 0.75mm, 1mm, 1.5mm, 2mm ), and cut them to the size of the scanner bed ( being careful to leave a space at the top, if you look at the film holders, there's always a "hole" at the top of the holder, this is the area where the scanner calibrates itself for each run ). Into the middle of each sheet I cut a 5x4 size hole, and once I'd wet-mounted a test trannie, scanned a small detail section using each shim in turn. I compared the sharpness on-screen of each scan. The shims also make great scanning masks, and with the offcuts you can make up some different aspect frames ( 5x4, 6x12 ) to stick in your camera bag to frame up shots

[Joanna Carter]

DJ, have you seen the betterscanning frames "in the flesh"?, they certainly seem to be a good idea, although I am thinking of trying to get some screw adjusters, to fit in the little rectangular holes, made for the original V700 holders. I should also be able to source the anti-Newton glass locally.

Your mention of using the left-over plastic to make viewing frames is something I had already thought of doing before I even thought of the scanner problems. At the moment we use a simple card frame on a wooden venetian blind slat; simple (read free ) but effective.

[buze]

Also note that when trying to find the proper "height" you should use different pieces of film, OR let the film come back to room temperature in between tests.
The light from the back raises the temperature of the film and sligntly changes it's flatness; so doing repeat scans to test sharpness is a moving target...

Alternatively you could pick a piece of scrap film for your tests, and blue-tak/tape it in place in the holder to make sure it's as tense and flat as possible...

[DJ]

I have no personal experience of the BetterScanning film holders. I'm waiting for him to finish the 5x4 one

[Dave Parkin]

I have noticed a number of references to "wet mounting" slides and negatives prior to scanning and wondered what is meant by the term. I am sure that it is very simple but seems daunting for a new starter in LF

Thanks

Dave

[dennis]

There is a new Epson scanner which was reviewed in the AP last week I think which utilises a wet mounting method, but it sounds very messy & time consuming - which digital is supposed to avoid . . . .

[Joanna Carter]

Dave, I personally have never found the need to wet mount transparencies in order to scan them. As far as I can see, the process is meant to keep the trannie flat and avoid some of the dust problems associated with dry scanning. It involves placing the trannie in a layer of mounting fluid on one sheet of glass, and then placing another sheet of glass on top; the fluid should avoid Newton's rings whilst allowing you to hold the trannie as flat as possible. If I am wrong, then someone more experienced is quite free to correct me

Dennis, I haven't seen the article, but suspect this would be the Epson V750. which I had gathered did not come with a wet mount kit, but things may have changed. In my opinion, wet mounting is messy and not worth the hassle. But don't forget that we are not dealing in pure digital photography, so a little mess is to be expected Digital scanning of images certainly saves a lot of mess but if wet mounting really does give better results, then that would be a small price to pay for not having to set up and maintain a complete wet darkroom.

[DJ]

Wet mounting is a process used on drum scanners, the film is adhered to the drum with (initially) surface tension with the fluid, and covered (sandwiched) with a sheet of clear acetate ( Mylar ) and more liquid. The liquid used is either oil, or a solvent, both of which are specially formulated not to hurt the film. What the fluid does is eliminate Newton rings, and also has the benefit of filling in small scratches and getting rid of dust (mostly). Also, Digital ICE et al doesn't work on B+W film, so fluid mounting is a good way to get rid of dust and scratches on B+W film scans.

Wet mounting has started to become popular on flatbeds because of the poor film-holders available. You can buy ready-made kits, or construct your own. I made my own and have had some limited success with it, though I haven't used it much.

The Epson 750 is the first "consumer" scanner to include this facility. When the 750 was announced, it was supposed to ship with the Fluid Mount Accessory included, which it did in the USA, but when it was released here, the FMA was conspicuous by it's absence. Epson said that it would never be released in Europe. They appear to have changed their mind, and now by registering your 750 with them, you will get sent one ( after some time, stocks are apparently very limited ). You can also purchase the FMA separately for £99, it works just as well with the V700, despite Epson's claims to the contrary.

YES, fluid mounting does in general give optimal results. YES, it's very messy, frustrating and a general pain in the a&$!.

[Dave Parkin]

Many thanks for the info re wet mounting. As I have yet to start scanning LF slides maybe I should learn to crawl before trying to walk and stick with Cibas

Dave

[DJ]

I was wandering around my scans directory today as I've some scanning of my Scotland shots to do, and I came across my calibration scans, so I thought I'd post them here to illustrate quite what a difference a small variance in distance can make...

These are all scans of the same area of a fluid mounted ( i.e. perfectly flat ) transparency, at various height differences from the scanner glass.

0mm ( directly on glass )


0.5 mm


0.75mm


1.0mm


1.5mm


2.0mm


When they're all lined up together in Photoshop, it's the 0.5mm one which is sharpest, but there's very little between it and the 0.75mm one. you can see the huge difference with the 2.0mm one though.

[DJ]

Was just reading an article where a guy worked out the actual depth of field of his Epson 4990 scanner. It was 0.04 inches, or 1.016mm...

Guess that means there's very little room for movement before things get out of focus.

[dennis]

Isn't life a little short to fuss over things like that? Dennis