DebAnn Loc: Toronto

If anyone is familiar with this scanner, I hope you can help me. I can't figure out how to get the scanner to produce a high-res file from strips of 35mm colour film.

Do I insert a large dpi number, such as 1200 or more - is that the trick? I don't get a large file if I enter 300 dpi. I would want to print something at about 8 x 10 at 300 dpi.

Thanks

BullMoose Loc: Southwest Michigan

I use the V600 and scan 35mm at 2,400. Not sure if this is correct way, but it's working for me.

Lots of info on the internet, and it seems like everyone has an opinion.

DebAnn Loc: Toronto

Thank you BullMoose - much appreciated.
Deb

Apaflo Loc: Anchorage, Alaska

Generally speaking you want a high DPI value if the image is to be printed.

To print an 8x10 at 300 DPI you need at least a 2400x3000 pixel image. To get 2400 pixels vertically when scanning a 1" (24mm) negative... obviously you need to scan at a minimum of 2400 DPI. To get the absolute best quality it should be scanned at twice the minimum DPI, so 4800 DPI would be the highest quality.

You might initially scan at a (very) low DPI just to allow configuring the scanner for where to start and stop the scan. Scanning at 75 DPI will show image coverage and won't take long for the scan. Once you get it exactly right, switch to at least 4800 DPI and make a production run.

DebAnn Loc: Toronto

Thank you so much Apaflo!

BullMoose Loc: Southwest Michigan

Your scanner should do a preview (showing you that the setup is correct and that the orientation of the film is correct in the holders) so you wouldn't have to scan at a lesser quality. After the preview, you can then scan at the desired DPI.

I tried 4,800, and it didn't make a noticeable difference from 2,400 for 35mm. I do scan at 4,800 for medium format to get everything I can out of that.

Apaflo Loc: Anchorage, Alaska

If your software does a preview that is fast, what it is doing is using a low DPI just as I suggested. If it isn't fast, switch to a low DPI.

If you are extremely critical, and want to preview scanned images with an editor that displays full screen (useful to see the edges at 100% or greater), do a regular scan as opposed to a preview, and use a low DPI.

That's a matter of Information Theory and I won't boor everyone with details. But scanning at twice the desired spacial frequency of image detail is required to faithfully extract that detail. It may not be terribly obvious on any particular image you scan, but if you know how to look for it there actually is a difference.

DebAnn Loc: Toronto

Yes, I did do a preview in the beginning and it looked OK. Later on today, I will scan them again at 2,400 and see how it goes. I might try 4,800 because I think I'll have to do some cropping of the originals - they're several years old and I wasn't as good a shooter as I am today! Thanks for your help.
Deb

BullMoose Loc: Southwest Michigan

Like I said in my first response, there's a lot of info out there and everyone has an opinion.

I was just stating what I've tried and what seems to work for me. Sometimes (make that most of the time), the technical reasons get in the way.

Apaflo Loc: Anchorage, Alaska

The issue with DPI in a preview is not how it looks, but how fast it makes the scan. Scanning, particularly with large prints and less so with small slides, is slow with high DPI rates. Using a low DPI for the preview is just convenience. If you are critical down to the very last pixel... the low DPI preview will not show the precision needed to position the document for a high resolution scan.

There is really little point in a final scan at 2400, unless you have many slides and your time is worth more than the results. The minimum for best results to print an 8x10 is 4800 DPI, but a higher resolution does not hurt and if the scan might ever be either cropped or printed at a larger than 8x10 size then 4800 DPI is not the best choice. The absolute best choice is always the highest DPI that the scanner can do. It's just slow, that's all...

Apaflo Loc: Anchorage, Alaska

Yep, everyone has an opinion... which may or may not be based on facts.

Information Theory is a fact though, not just an opinion. Technical reasons get in the way of ignorance..., but they release creativity!

Here are three Wiki articles that will clarify this for anyone actually interested in facts:

TriX Loc: Raleigh, NC

Our old friend Nyquist (digitizing/sampling at 2x minimum of the highest frequency component is required to accurately reconstruct the wave form...)

selmslie Loc: Fernandina Beach, FL, USA

Your observation is consistent with rigorous testing done by an authoritative tester of scanning equipment: http://www.filmscanner.info/en/FilmscannerTestberichte.html

Based on my own observations of extensive use of a V750 scanner I have found that it is optically limited to about 2400 DPI. That's great for medium and large format film and prints but it generates an image of under 8 MP from a 35mm slide or negative. That's enugh to produce an 8x10 print at 300 DPI. Doubling the scanner resolution setting quadruples the megapixels and file size but does not produce a visible improvement in resolution.

On the other hand, a dedicated film scanner is likely to produce a genuine improvement in resolution based on a higher optical resolution. I use a Nikon Coolscan 9000 for 35mm and medium format that generates a legitimate resolution of 4000 DPI, over 21 MP for 35mm and about 70 MP for 6x6. There are other dedicated film scanners that can produce resolutions of 3200 DPI (nearly 14 MP) as well as some expensive scanners that will scan film at 6000 (48 MP) or 7000 DPI (65 MP) or more.

Nevertheless, the best film I can get my hands on is still good for only about 21 MP from a 35mm negative.

Apaflo Loc: Anchorage, Alaska

It is consistent, but there is no discussion of what how to decide what resolution to use. All the discussion provides is figures for maximum actual resolution obtainable from various different scanners. That is actually two different subjects...

All of which is to say, that as suggested in previous articles the ideal scan rate to produce 8x10 prints from a 35mm slide would be a minimum of 4800 DPI. It is, granted, a good point to add that any given scanner many not actually be able to produce an image with 4800 DPI resolution despite settings for even higher resolution. The question then becomes one of does it actually make any difference, and if so what does it take to benefit from setting a higher scan rate?

The cited article helps only with listings of the maximum actual resolution, but doesn't provide any discussion of the topic past that. A specific discussion about what resolution to use can be found in a PDF document from Plustek, which also references another document from the Federal Agencies Digitization Guidelines Initiative Still Image Working Group. Plustek recommends, "Going by these specifications, it means that you should scan at a minimum of 3600 dpi on a Plustek
OpticFilm 35mm scanner."

Note that both Plustek and the previously cited article mention SilverFast scanning software. Not on that specific page cited, but elsewhere on that site there is more information about what SilverFast software does to produce better scans. But there unfortunately is not a generic discussion of what else can be done to optimize scanning for different purposes.

Regardless of which scanning software is used, scanning at better than 4800 DPI produces files that can be post processed for the best results for any given purpose. That is true primarily because the maximum resolution of 35mm film can reasonably be assumed at about 2400 DPI. The resulting output file from the scanner may or may not actually be able to produce resolution equal to 4800 DPI, but for a 1x1-1/2 inch scan area it will produce a 4800x7200 pixel image that can be used, at 240 PPI or more for printing at 20x30 or smaller without re-sampling to a larger pixel dimension. Obviously it will need to be re-sampled to a smaller pixel dimension for sizes like 8x10. That is where the benefit from oversampling with the scanner comes in. Ideally one would not use an Adobe software, all of which use Bicubic Sharper, for re-sampling. Nor should it be left to the print driver, which might even be worse. Something like the tools from ImageMagick package, where a wide range of different filters are available, is optimal. For most images using a Lanczos filter or a RobidouxSharp filter would be acceptable.

There is a lot more to getting the ultimate scan from an image than is easily found even with Google. Some of it is obvious, some is not. Obvious: a slide copier mounted on a Nikon D800 or D810 camera will produce a better image file than virtually any scanner for the same price. The 7360x4928 pixel file is essentially a 4928 DPI scan.

selmslie Loc: Fernandina Beach, FL, USA

The OP is not looking for the ultimate scan, just a scan that will produce an 8x10 from a 24x36 mm negative. When you do the math that's only 1.34 square inches of negative, less for a mounted slide. Even cropped to 8x10 proportions, a 2400 dpi scan is adequate since it will get you close to 285 dpi for the print if you don't crop any further. 4800 dpi is a waste of pixels.

Practical considerations outweigh all of the theoretical speculation. A flat-bed scanner does not focus on the film. It relies on the film holder positioning the film at the correct height above the glass. Scanning beyond the optical limit of the scanner will not improve this. The V750/V850 is touted to produce a resolution of 6400 dpi x 9600 dpi. That will produce a bigger file but not a better scan.

A consumer film scanner actually auto-focuses on the film itself (at least my Coolscan does) so it can achieve a more precise optical resolution. At 4000 dpi, grain is already visible in all but the very slowest B&W film. The resolution for color film is different in that the color is produced by overlapping dye clouds rather than grain clumps or particles. Color is less precise than B&W.

Drum scanners can produce even higher resolutions than ordinary film scanners but they are extremely expensive and often involve fluid mounting of the film - far more trouble than it is worth for ordinary scanning.