Scanning negatives resolution

[bounty]

Hi, I have been scanning undreds of negatives since I bought my Epson V 700 scanner
last month and what a difference in time when scanning let's say some 35 mm at 4800 DPI vs 6400 DPI. I know, I know the more resolution the better (to some extent)
Well, would I see it if I were to enlarge a 35 mm at 11X14 with a 4800 and 6400 DPI or any other negative for that matter?
I don't see a difference on my monitor, but I know that I shouldn't see it unless I reall print them.


Bounty

Thanks

[Brian Ellis]

From all I've read here and elsewhere, you don't scan at the highest number of ppis at which the scanner is capable of scanning. You scan at the highest number of ppis that the scanner is capable of resolving. I think tests have shown the V700 is capable of resolving something like 2200 ppi. If that's the case then scanning at anything higher than that (or whatever the actual # is) is just unnecessarily increasing the file size. But frankly it doesn't matter a whole lot what you do if you're trying to make 11x14 prints from a scan of a 35mm negative with the V700, you aren't going to get a good 11x14 print from a 35mm negative with the V700 (unless the V700 is a vast improvement over my 4990, which I don't think it is based on the reviews I've read). The scans might be fine for the net or for small family snapshots but not for good 11x14 prints by most people's standards.

[Ken Lee]

A general rule of thumb is that you should print at 360 ppi on Epson printers, and 300 ppi for Canon. Dunno about others. This will give you good results from your printer.

Some photographers are more demanding, and insist that they can see better results by doubling the resolution: 720 instead of 360, etc.

By sending data to the printer in its own optimal resolution, you avoid dithering: jagged lines.

Let's say you print on an Epson printer, and you scanned your images at 3600 ppi. Since 3600 / 360 = 10, you can make a 10X enlargement, and expect your image to be critically sharp.

This presumes that the original image is critically sharp, and that your scanner actually delivers 3600 ppi. Most consumer-grade flatbeds deliver around 65% of their promised resolution. So an 8x10 from a 35mm slide, is pretty good.

Keep in mind that even a superb lens, when enlarged by 10X, will show 1/10 the sharpness. So an ideal 35mm lens that gets 80 lpmm, delivers 8 lpmm when enlarged by 10X. Compare that to a good lens for 4x5, which might deliver 60 lpmm. When making an 8x10, it gets enlarged by 2x, and delivers 30 lpmm, which is so sharp, the eye can't see all the data.

Beyond that, you have contact prints, where there is virtually no loss. Now your images have so much visual information, it's... a delight to the eye.

In a nutshell, if you really have 2160 ppi to deal with, you can make a superb 6X enlargement.

[sanking]

Brian and Ken make important points.

Most people new to scanning don't immediately understand that the stated resolution of consumer flatberd scanner is not "effective resolution". The CCD may be capable of imaging the resolution but other factors, quality of the lens and its covering area, for example, limit the effective resolution to a much lower number than the advertised. The experience of most people who have actually tested the 4990 and V700 with targets is that the best you can do with these scanners is about 2000 ppi and 2200 ppi respectively.

And you get about that if you scan at 2400 ppi. Scanning at 4800 ppi or 6500 ppi may increase effective resolution slightly, about 10% in my experience. However, when you weight the slight increase in effective resolution again the dramatic increase in scan time, and the resulting file size, you may find that scanning at the higher ppi is not worth the trouble.

There is one advantage to scanning at a higher ppi and then downsizing, and that is you will reduce the amount of noise. Scanning at 4880 ppi versus 2400 ppi gives four pixels to one. If you then downsize it will average out the noise, and since the noise is usually only in one or two of the four pixels the net result is that downsizing gives less noise. I think this would be useful with 35mm and medium format material where the final file size would be less important than doing everything possible to optimize quality of the scan.

Sandy King

[bounty]

I am surprised by you comments, because I heard on this forum that 35 mm should be scanned at 6400DPI, 2 1/4 4800 and 4X5 and 4800 or 2400


See the Epson V 700 SCANNER thread posted on this forum a couple weeks ago

and epson v 700 review on google

bounty

[David Luttmann]

I'll echo Sandy's comments. Scanning at higher resolutions adds little to the real scanned resolution, but it does allow for the benefit of downsampling to reduce noise. By downsampling from a 4800ppi scan down to, 2400 for example, noise can be a bit less and you can obtain higher perceived sharpness when using bicubic sharper for the reduction.

[Ken Lee]

"I am surprised by you comments, because I heard on this forum that 35 mm should be scanned at 6400DPI, 2 1/4 4800 and 4X5 and 4800 or 2400"

Many people who deal with 35mm and Medium Format film, use dedicated film scanners, such as the Nikon 9000 series. Or, they use high-end scanners that can handle just about anything.

[Walter Calahan]

Use a film scanner such as the Nikon 5000 or 9000.

35mm on my Epson V750 looks like crap compared to my Nikon 8000.

[Leonard Evens]

You have to make a distinction between the scanning resolution, in terms of samples per inch and effective resolution in terms of the ability to distinguish fine detail. For 4 x 5, he V700 is capable of collecting 4800 samples for each horizontal line and stepping through 9600 horizontal lines per inch. Since you can't scan separate the horizontal and vertical resolutions, the best you can ask for is 4800 samples per inch in both directions. If the optics ad other mechanisms of the scanner were perfect, according to digital processing theory, you could reslve 2400 lie pairs per inch. (You need two pixels per line pair.) In metric units, this is the same as about 94 lp/mm. Were the scanner that good, your scanner would in effect detract little from what your lenses and film can deliver. But unfortunately, the scanner is far from perfect, and in fact, according to reports, what you get is something in the range 30-32 lp/mm.

You can scan at a lower resolution or you can scan at 4800 ppi and then reduce to a lower resolution in a photoeditor such as Photoshop. One can make arguments for either. But keep in mind that the scanner hardware, most likely, is going to scan at 4800 ppi in any case and then either the firmware or the scanner software is going to downsize to a lower resoltuion if you request it. You may be better off doing this in the photoeditor which will probably do a better job of downsizing.

[Daniel_Buck]

I scan at 2400 for my printing. I did a test where I scanned 4800 and downsized to match the 2400 scan (this on my 4990) the difference was very minor.