Scanning photo-negatives .. what can I expect

Hi James,

As I understand it, it's extremely unlikely that the scanner (especially flatbed) resolution is 4800x9600. It is important to understand the true 'optical' resolution of the scanner, and not the 'interpolated' resolution as is frequently quoted. For example, if indeed the optical resolution of this scanner is 4800 (which I'd be slightly sceptical of, although technology may have moved on considerably since I bought mine), the 9600 is almost certainly interpolated.

The scanner is unlikely to interpolate the image as well as a decent image processing applicaion, for example, Photoshop. Therefore, find out what the true optical resolution is, and only scan at this resolution. Then, if necessary, interpolate (or 'resize') the image later using a decent application.

This should be quicker.

When working out the resolution you need, consider the following. If you were to print the image at approx A4 size, this is about 7 times the size of a 35mm negative. Therefore to preserve the pixels you scan (as you'll need to resize from 35mm to A4), you need about 7 times more resolution than the print resoltion. This is likely to be about 600dpi, therefore about 4200 dpi is needed in the scan if you are to preserve the 'original' pixels. I think!

The green tint is likely to be correctable, and it probably down to the light in the scanner lid not being 'white' enough. It's akin to a 'white balance' setting being wrong on a camera.

I have an Epson floatbed scanner and have achieved reasonable results. I'm happier with Black and White than with colour however.

I haven't used a dedicated film scanner, but a good friend insists that they're better than the flatbed variety. Although they rely on pretty similar technology, a white light, some lenses, a row of optical sensors, and a fine stepper motor, I can believe that the dedicated ones are better.

Ken Rockwell's site here:

http://www.kenrockwell.com/tech/scantek.htm

talks through some of the issues, but you may be able to find more information elsewhere.

You may want to try scanning at a lower resolution, as more pixels isn't necessarily adding more resolution - especially if your film is more grainy - ie 400 ASA or higher... Try 1600 or 3200 and compare the results. What resoltion you use depends on whether you simply intend to view the photos on your monitor, or print them.

Apologies if you knew all this already, and good luck!

Cheers,

phil

The whole spector of pixels and resolution is amazingly complicated.

If you intend printing at home then a printer will throw out at oleast three quarters of that 4000 result, infact even today most printers with supposed massive DPIs lose any improvements after 300dpi anyhow.

If you intend getting the prints blown up then scan at no more than 600, if you scan at full res on an inexpensive scanner what you will get is a really high quality fuzzy image.

Trust me on this, 300dpi for home prints, no more than 600dpi for anything else.

quote:

Originally posted by James Hamilton:
I know I can buy dedicated negative/slide scanners. What sort of speed do they operate at ? And what is the quality like ?

I have a dedicated 35mm film scanner and it's scanning speed and quality are pretty good, despite it being a long way from the latest model. My scanner (a Minolta) allows me to get through scanning several films in an evening and the quality is excellent - in many ways significantly better than my DSLR is capable of.

There are a couple of very competent film scanners currently available with street prices of £200 or less - one of those was reviewed in Amateur Photographer a few weeks back and they were very impressed with it.

quote:

Originally posted by garyi:
The whole spector of pixels and resolution is amazingly complicated.

If you intend printing at home then a printer will throw out at oleast three quarters of that 4000 result, infact even today most printers with supposed massive DPIs lose any improvements after 300dpi anyhow.

If you intend getting the prints blown up then scan at no more than 600, if you scan at full res on an inexpensive scanner what you will get is a really high quality fuzzy image.

Trust me on this, 300dpi for home prints, no more than 600dpi for anything else.

Gary, if you scan a negative at 300dpi, you end up with a photo which is 35mm in size, and has 300dpi. When you enlarge it to, say, A4 size to print, it will only have 40dpi (without interpolating), surely this isn't enough?

Phil

Hi James,

I used a Nikon coolscan to scan a bunch of slides and negs in 97, the quality was great, but it was a bit slow. I understand that they are much faster and even better quality now. Since then I have scanned slides many times on flatbed scanners and the quality was not even close.

I would really recommend a dedicated slide/neg scanner. The scanning software they use is also different, and is much better for negs/slides.

Regards
Nathan

I've used Minolta slide/negative scanners to scan in hundreds of slides at work, and the quality is very good, and not TOO slow...

My HP scanner (with built-in negative/slide scanning attachment) is fairly crap at scanning negs, though I've not tried slides in it.

I'd go for a dedicated slide/neg scanner if you've got a lot to do

If the image size is multiplied by 7, don't you have to multiply dpi by 49 (7 squared) to get the same resolution?

For example, 600dpi is, say 20 x 30 dots. You would need 140 x 210 dots which is 29,400 or 49 x 600dpi.

Init?

I must confess I did not consider the size of the negative when giving advice I was thinking photos and such.

Never the less its best to try, scan a neg at 600DPI then print it at a larger size and see what you get. DPI seems to be as misleading as WATTS.

quote:

Originally posted by 7V:
If the image size is multiplied by 7, don't you have to multiply dpi by 49 (7 squared) to get the same resolution?

For example, 600dpi is, say 20 x 30 dots. You would need 140 x 210 dots which is 29,400 or 49 x 600dpi.

Init?

The DPI figure is linear, not a square (as you've suggested). In your example there'd only be 20 linear dots per inch. You could see them!

Phil

Thank goodness for that. I was getting quite confused.

It's interesting that in the area of PC power and memory, we can probably go on improving for ever, in the area of sound quality we'll never reach perfection but when it comes to resolution there seem to be finite limits beyond which we won't be able to see the difference (at say A0 poster size).

Or am I wrong here?

First -- sorry for starting this thread and not being able to reply for the past few days.

Second -- many thanks for all the advice. I think I probably need a dedicated negative scanner and I will probably wait a bit before buying one.

Thanks again

James H.

James,
As an alternative there are firms that will do the job for you. I used the outfit below with good results. But professional scanning does reveal flaws and deterioration in your transparencies.
http://www.slidesoncd.co.uk/html/prices.html
David

Thanks David, usefull stuff. I will probably wait a while before doing anything. Appreciated advice.

James H.

The Reflecta DigitDia 4000 Scanner (SilverFast) was given a good review in the one photo mag I read. The kit supports the use of CS, Universal, Braun and LKM 50 slide magazines and so allows the user the luxury of doing something else while the machine works through 50 slides.
Times quoted in the review are

quote:

The scan time for a magazine of 50 slides is 24 mins for 250dpi/750K files or 87 mins for 3000dpi/34MB files.

.
More details at http://www.nativedigital.co.uk/

Worth a look?