3200dpi v 2400dpi for medium format

P

pioneer31

Messages
53
Edit My Images
No
I have scanned an absolute shedload of medium format B&W negatives at 3200dpi at 16 bit on an Epson V750. They were taken between 1935 and 1960, not with the world’s finest lenses!

The negatives are assorted and measure 5x7, 6x6 and 6x9.

I’d like to resize them to 2400dpi as the 3200dpi ones have generated very large TIFF files (some heading towards 200MB) I want to keep them as TIFFs but would like the files smaller.

I’m not intending to print them but if I did, they’d just be the size of an ordinary family album photo. They will be viewed on a PC screen and possibly on a much larger LED TV.

Will I notice any difference if I drop them to 2400dpi (without resampling). Was there any point scanning them at 3200dpi in the first place?
 
Just my two penny worth - however I would rescan at 300-600dpi and see if you can see the difference on a screen, compared to the 3200/2400dpi - I think you will probably find that the quality difference is marginal, the size difference massive. Also unless you are going to be editing them, resizing, cropping etc, why not just save them as a high quality jpg as again I doubt you will notice much difference based on what you are doing with them. Good luck regardless.
 
pioneer31 said:
Will I notice any difference if I drop them to 2400dpi (without resampling). Was there any point scanning them at 3200dpi in the first place?
Click to expand...
Probably not.

6x9 negs (worst case scenario from your OP) at 2400ppi = 266ppi resolution for the final image which would be absolutely fine for pretty much anything apart from close scrutiny by a pedant (or photographer) with 20/20 vision and a magnifying glass. I've printed to 12 feet long at around 100ppi and even up close couldn't see a difference. For reference, your original files at 3200ppi for 6x9 = 350ppi which is OTT for anything other than a billboard print for a major company ad where they are going to stand right next to it and look for imperfection. Even then, I'd probably sigh at them.

Viewing distance makes a huge difference to ppi requirements, and assuming you are looking at the telly from 6ft away, your eyes (assuming 20-20 vision) can't resolve more than about 50ppi which for your 6x9 negs means 450ppi as a scan setting. I have the source for my numbers but the website went offline a few years ago. It was done by a photographer-optician, and assumes an average pixel size in microns [that I don't have to hand], but in real world terms it made a ton of sense to me. I think their study concluded that the absolute best the human eye could resolve was about 800ppi at a distance of 4 inches. Once you get to 12 inches (reading distance) it drops to 300 ppi, then 115ppi at 30" (standard monitor distance), 50ppi at 6 feet (TV viewing distance), and a mahoosive 7ppi at about 40 feet (a cinema screen).

If you think about it, imagine taping a ruler to a wall, then going and standing 40 feet away and trying to spot the 1/8 inch markings.

Hope that helps!
 
Last edited:
theghostie said:
Just my two penny worth - however I would rescan at 300-600dpi and see if you can see the difference on a screen, compared to the 3200/2400dpi - I think you will probably find that the quality difference is marginal, the size difference massive. Also unless you are going to be editing them, resizing, cropping etc, why not just save them as a high quality jpg as again I doubt you will notice much difference based on what you are doing with them. Good luck regardless.
Click to expand...
This!

I can't see any reason for scanning 120 negatives at more than around 1000 samples per inch for most domestic use. If you think about it, images on here are 1200 pixels across, so if you started with a 6x9 (centimetre) negative (2 1/4 by 3 1/4 in inches, roughly), you're looking for 400 pixels per inch of negative! And yes, for this kind of use, JPEG is just fine.
 
Should I resample or not? Some seem to say yes and others no (because it degrades the image apparently)
 
You want to scan at about 2x the resolution of the source... what are the chances there is anywhere close to 1200 dpi resolution (smallest size detail) in the negative to justify 2400dpi scan?

FWIW, the whole 300ppi for print thing started with scanning negatives; where DPI scanned becomes the PPI of the image.

I would resample as long as the results meet the requirement... but it's fuzzy math and a rescan might generate better results.
 
They aren't fantastic quality, plus I have about 800 or so images. I can't face doing them again, so I'll just convert them.

I'll do a test, one with resampling, one without, I have heard conflicting information about which method is best.
 
If you do a batch convert, time doesn't matter, so why not just resample?
If it wasn't done at the time of scanning, you could also add auto levels into the convert, which usually gives a good starting point for tweaking later.
 
Sangoma said:
If you do a batch convert, time doesn't matter, so why not just resample?
If it wasn't done at the time of scanning, you could also add auto levels into the convert, which usually gives a good starting point for tweaking later.
Click to expand...
You could try using xnconvert, a batch image converter. I used it to change my black and white film scans from the greyscale colour space to RGB, but there are lots of other things it can do, including resize. It's free, IIRC, give it a whirl!
 
You must log in or register to reply here.
Back
Top