Avoiding file size overkill while scanning.

[jordanstarr]

I just bought a Nikon 8000 for 35mm and 120 format and borrowed my friend's Epson V700 for 4x5 film. I'm a newbie to scanning somewhat so I'm not 100% sure if I'm doing this right, but I feel like I'm running into a problem with file size though. My Nikon is giving me (@4000 DPI scanning):

35mm (grayscale, 14-bit) - 38MB average - 18"x12" at 300 DPI print size
120 (grayscale, 14-bit) - 160MB average - 35"x27" at 300 DPI

Epson v700 is giving me (@6400 DPI):
4x5 (grayscale, 16-bit) - 600 MB average - 96"x75" at 300 DPI


I have a decent idea on how all this stuff works, but these file sizes seem a little large to me. Ideally what I am trying to do is scan one file at it's best and then edit it to print size when I need a particular size. So, I'm looking to balance on the line between quality and file size and I'm not sure if I'm doing it right. I might have to explain my workflow in more detail, so let me know if I need to do that.

A couple other questions I have are:
Is scanning at 6400 on the Epson v700 flatbed overkill?
Is there any advantage to having let's say 400DPI for print quality (even if the eye can only see 300 DPI)?
Is there something I should change to my workflow to get my desired results?

I'm usually an APUGer and use the darkroom, so this is my first post here. Thanks in advance for your help.

 

[OldBikerPete]

Those file sizes seem reasonable to me.
The best 35mm and medium format lenses can resolve over 90line pairs per mm on the right film --> 4572 dots per inch. To fully resolve this you would need to scan at double that resolution (9144dpi) then reduce the image size by 50% linearly back to 4572dpi in photoshop or similar. So scanning at 4000dpi (although the best you have available) will mot do full justice to the best optics.
Good large format lenses can resolve 60lp/mm on the right film -->3048dpi so scanning at 6400dpi on a scanner which is optically capable of 3200dpi is adequate and you should reduce the image size again after scanning in Photoshop.
I think most in the know believe that the optical capability of that Epson scanner is much less than 3200dpi, so you could reduce your scanning and storage reolution appropriately.

 

[pellicle]

Hi

well, if you take the scan once philosophy ... but then how much do you want to pay in storage?

I treat my negs as my storage, and scan them again as I wish to print again. My technique has improved over the years so stuff which I scanned in 2003 looks dodgy to me now

as to the file size, remember that if you're scanning at 16 bits the file size will be double what you may be thinking of otherwise. Myself I'd do most of the rough adjustments (getting it close, putting on the appropriate colour space) and then store at 8 bits ... but then what I'd really do is rescan it

I don't think that the V700 will really be giving you 6400DPI from your film, so you may as well scan at a lower level and upscale in software if you need something massive (remember that 3200dpi scan and then printed to 300dpi is a x10 enlargment of your film)

 

[Rudeofus]

Arguing from a pure signal processing standpoint: I would scan at the highest possible resolution so I can avoid anti aliasing artefacts much easier (knowing the lens of the V700 is way too soft to do 6400 dpi, hence acts as an effective AA filter). I would also expect to have better noise performance if I scanned at max res and lp filtered and downscaled in software afterwards. Obviously, after the initial PP steps it would make sense to downsample the image to its real/necessary resolution, especially before moving it to long term storage, backup drives and what have you.

 

[cupcake_ham]

The most you're going to achieve with the V700 is about 2600ppi (not DPI). It's best to scan with the higher rez optic in the 6400spi mode, and then downsample to 3200ppi. That's going to give the best results without the file size bloat.

 

[jordanstarr]

OldBikerPete:
I never thought about lenses before in terms of line pairs per mm. That throws me into a whole new tailspin. Then what you're saying is that at scanning 4000dpi I'm not using the full potential of what I'm shooting? It's a good thing most of my stuff is darkroom prints then if that's the case.

pellicle:
I'd like to pay as little as I can get away with, without sacrificing quality of the images. Thanks for the formula too, I never knew that one.

Rudeofus:
Everything you said is pretty much over my head, but gave me a lot to research. I appreciate it and will probably appreciate it more when I can figure out what it all means.

David:
Thanks for the reality check on the v700 and the advise that followed. You've saved me lots of hard drive space.

 

[Rudeofus]

Everything you said is pretty much over my head, but gave me a lot to research. I appreciate it and will probably appreciate it more when I can figure out what it all means.

Sorry for the confusion, I'll try to explain it here:

Aliasing effect appear, if the signal you sample has such a fine structure that your sensor has insufficient pixel density to capture it. As a result you don't just lose detail, instead your sensor may actually create artefacts, sometimes referred to as moir patterns. There's also a nice wikipedia article for aliasing. If, however, the lens of your scanner is so soft that fine structures get sufficiently blurred, you avoid these artefacts. Picking the highest resolution of any modern flat bed scanner pretty much ensures that the lens does work as effective anti aliasing filter.

The second topic I brought up was noise. Like digital cameras, scanner pixels can be noisy and computing the average of several pixels yields better results than just taking fewer samples.

Both arguments (for which I have lots of theory but much less scanning related experience ) boil down to what others have recommended: scan at the highest scanner resolution, then use a decent graphics program to resize the image to a smaller resolution.