Tuesday, 12 June 2007
This past week I've been working on scanning the LF work from my trip to the Lake District. It's been a voyage of discovery. As part of the initial work, I've been experimenting with getting the best from my scanner (an Epson V750 Pro flatbed), working through the vast array of variables on offer with the SilverFast scanning software it came with.
This is what I've found (so far):
Resolution - the scanner has 2 lenses - 4800dpi and 6400dpi, with output up to 9600dpi. Obviously for a 4x5 sheet I'm not going to go that high but the question is how high and is there some sort of optimum? I ran tests at 1200, 2400, 3600, 4800 dpi (on small sections - the last would be a monster file if I tried the whole image). I was looking for maximum amount of detail. At 1200 it's useless at any size - a lot of pixelation, limited detail, only good for document scans. 2400 renders good detail, smooth at 100% on screen. 3600 yields more detail than 2400, again smooth results. 4800 shows no more detail that 3600 - it's effectively a native enlargement. I think at 3600dpi it could be getting to the limit of the film.
Focus - the film holders can bet set at different heights to get optimum focus. This is important. In focus 2400 is as good as out of focus 3600. It's not just in clarity and detail, colour saturation and contrast are better too. Interestingly, the height settings for the 6x9 and 4x5 holders work out different. Not sure why.
Sharpening settings - there is a huge array to pick from. In the end I've settled for a light USM setting as giving consistently good results across the whole image. As I'm using fine grain film (Fuji Astia & Provia 100) grain effects are limited and easily removed in processing.
Number of passes - this thing can do up to 16 passes. I tried up to 8. There was slight improvement from 1 to 2, nothing noticeable beyond that. I tested by scanning a dark area then expanding with curves until near posterization. No real difference in noise that I could tell beyond 2 passes. Downside of lots of passes is the film gets hot and starts to buckle, seriously degrading results.
Dust & scratch removal - Digital ICE is built in and there are a couple of other options. I'm not touching them for the large stuff. It's easily removed in processing if I clean the surfaces before scanning. I found ICE froze the computer when trying an entire 4x5. Cleaning up only takes 5 minutes - I'm using selective application of dust & scratches tool in PS.
Would I want a drum scan? Can't see why. I get fine resolution towards the limit of the film, scanning to easily produce 40" plus enlargements from a 4x5 with smooth tones, limited grain and good saturation and contrast. I'm finding I need very little processing to get excellent results.
Explanation of the crop with which I've illustrated this post: this is a detail from one of the shots I've been working on (straight from the scan with a little extra sharpening). it shows a building amongst the trees in the valley. What's the big deal? I've been to this spot many times and didn't know it was there. I'm pretty sure I can't see it with the naked eye yet I'm picking it up clearly with a 120mm lens on 4x5 (that's fairly wide) and easily picking it up on the scan. Does one need better results than that?