Curved film causing scanning issues

Oatcake

Oatcake

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Matt
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I have a scanner with an automatic film feeder (no film holder) and I'm having problems with some agfa pro 200 that has dried very curved and wont lie flat. It's causing my scans to be out of focus. Any ideas on how to flatten it?

Matt
 
srichards said:
Large heavy books? Steam roller?
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Currently under books now. Has been all afternoon since I took them down off the shower rail. No joy yet though. Any idea on how long it'll take?

Also, how might I ensure negs dry straight when they are hanging. Ideally I'd like to keep them as the full roll to make the most of my scanners auto feed capabilities. At the minute I'm using pegs with a couple of 2p pieces gaffa taped to them as weights. Will properly designed weighted clips make any difference? Obviously the pegs are only holding the film in the centre of the strip and it's allowing the edges to curl up. I did hear you could reverse wind it back onto a spool once it's dry to try and help.
 
Reverse winding will only help with longitudinal curl. Sounds like yours is curling side to side. Drying slowly is the best prevention in my experience. I think weighting the film all afternoon is probably not long enough. Give it a couple of days.
 
Proper film clips do work better. I don't generally have a problem with curly negs when using them.
 
It seems logical to me that when a film dries and the material has a propensity to curl, preventing it curling along the long edge will force it to curl along the perpendicular axis. Hence, I'm wondering whether the weights on the end actually increase the curl across the short width? I.e. no weight = the film curls 'up' in an attempt to form a spiral, and this prevents the curl you've experienced.
 
I use metal bull dog clips when hanging film in the shower cabinet. Top one is attached to the top rail via a rubber band, lower one simply grips the film and acts as a weight. For film like Tri-X that wants to curl across the width of the film, I sleeve them in 6s and place the sleeve under a large flat heavy (photo) book for around 24 hours. It seems to be reasonably flat after that. However, the Plustek film holders grip the edges and in between each frame, so curl is generally only a problem getting them into the film holder.
 
I was just reading Miniature Camera Magazine, the June 1938 issue, and the advice given there was that if the film is wound with the emulsion side outwards and left for some time (preferably two days) it will then lie flat. I've never tried this, and obviously it's intended to be applied immediately after the film has been first dried. This isn't the result that John (post 4 above) would expect, and I'm only passing on a result with pre-war films.
 
This seems to have become more of a problem as film bases have changed over time.
In the 50's and 60's film flatness improved greatly and always seems to dry flat in both directions, if hung with proper film clips.
Since then the base material has changed several times as has the back coating on some films. The more recent films seem to be both thinner and curl more.
I am not sure that there is an answer apart from sleeving them up and pressing them.
 
I think it varies a lot by film. Tri-X tends to curl sideways, the Acros 100 roll I devved recently had quite a curl. I think some Delta I did last year was amazingly flat; I have one roll of Delta 400 awaiting dev so can report on this.
 
I'm not experienced with many different film types (basically just three!) but in my experience the smaller the film, the greater the curl. My 5x4 FP4 sheets are flat, my FP4/PanF 120s curl very slightly. When I used 35mm (years ago) that curled far more than I experience now, and across the short dimension of the film.
 
Update: I'm still having problems with my vista 200 curling, I've taken to reverse rolling shortly after drying and putting it into a film canister but it still retains some curl even after a couple of days.
 
Oatcake said:
Update: I'm still having problems with my vista 200 curling, I've taken to reverse rolling shortly after drying and putting it into a film canister but it still retains some curl even after a couple of days.
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h'mm I've had umpteen rolls done at Adsa and are perfectly flat......maybe it's because the dev m\c heat dries them quickly and holds them straight? Just thinking, if a hair dryer was used maybe when dry and warm immediately place in a heavy book (might increase dust spots if used by the family).....I've used a hair dryer in the past but wasn't worried about curl as they were used in an enlarger, anyway the heat from the enlarging lamp probably curled them slightly while printing....esp my first enlarger with 100w bulb and condensers :eek:
 
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The rolls of expired film I've used all seem to have had some degree of latitudinal curl. The way I've gotten around this when scanning (on my flatbed) is by placing a small paper wedge under the negative holder in the scanner to lift it just enough to avoid contact with the glass. This has worked ok so far and hasn't resulted in any noticeable focussing issues in the scans. Not sure that this is any help to the OP though.

The roll of 135 Rollei Retro 400s I shot a few weeks back had a severe longitudinal curl and it was a real fight getting the 6-shot strips into the negative holder. I needed three hands!
 
I'm using a scanner without a holder so it just sucks in the negs as they are so they need to be close to perfectly flat really
 
Oatcake said:
I'm using a scanner without a holder so it just sucks in the negs as they are so they need to be close to perfectly flat really
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No problems with Newton's rings?
 
IMG_0150.JPG

These have been in a film canister rolled against the curve since Saturday night and put near the radiator for a bit of warmth. Made absolutely no difference at all haha
 
Oatcake said:
Newton's rings?
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Not sure if that's the right name... supposedly if you scan film directly on the glass you get optical fringes showing due to the very slightly differing air gap between different parts of the film and the glass (I realise that description goes beyond simplification into wrong, but it'll have to do until someone corrects me). You can get special glass film holders that are somehow treated to avoid the effect, and I think it's one of the reasons why high quality scans are wet mounted.

But if you're not seeing strange artefacts on your scans then I guess it's OK.
 
ChrisR said:
Not sure if that's the right name... supposedly if you scan film directly on the glass you get optical fringes showing due to the very slightly differing air gap between different parts of the film and the glass (I realise that description goes beyond simplification into wrong, but it'll have to do until someone corrects me). You can get special glass film holders that are somehow treated to avoid the effect, and I think it's one of the reasons why high quality scans are wet mounted.

But if you're not seeing strange artefacts on your scans then I guess it's OK.
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No nothing like that (I googled newtons rings so I know what you mean now). My scanner cant hold the film very flat because there is no holder. It just pulls them through a motorised feed over the glass. So with the curve of the film the centre of the frame is sitting higher than the top and bottom of the frame which is causing focus issues I think.
 
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