Epson V700 vs 4990

[Frank Petronio]

What Ted said, they are all a tremendous value for what they are. I had bad luck with quality control on the Microteks, and the progression of Epsons I've had make steady subtle improvements. What is limiting is the crappy Epson software and I do need to try Silverfast. I've been using VueScan and it is too bizzare for color work (it's fun for B&W though!)

I'd save my money and buy Imacon scans for the big stuff. I perceive a subtle improvement between the 3200 and 4990 scans, but I am still working with scans from my old 1600 model that are fine and I don't feel the need to rescan old work because the scanners are so awesomely better.

[Henry Ambrose]

Well, I must have had a "bad" 4870 and a "good" 4990 as I used them side by side on the same film and could definitely see a difference. I never owned a 3200 to compare to these two. I'd still assume improvement with a 4990 over a 3200. Saunders found otherwise in his experience.

I'll claim unit to unit variation has something to do with this along with focus height variatioins. If your Epson flatbed (or any other maker) is not doing as well as you think it should, I suggest you experiment with film height from on the glass and in small increments above that. Somewhere in there you may find a sweeter spot.

Leonard, I'll make another scan and let you know what happens. This time 4x5 at 3200, 48 bit just as you wrote in the original post. That's about a 1GB file I think, pretty darn big to work with unless you're making huge prints and really need it. I've been making really nice 24 inch wide prints from 4x5 scans done at 2400 ppi. Those files are pretty hefty for my older Mac.

[Doug Fisher]

>>I'll claim unit to unit variation has something to do with this along with focus height variatioins.<<

I think you hit on the most likely reason for any variation in sharpness you observed.

Doug
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www.BetterScanning.com

[Leonard Evens]

Thanks for all the information. If indeed either the Epson V700 or the 4990 can deliver close to 2000 spi, that would be a 33 percent improvement in resolution over what I find I can do with my Epson 3200. Unfortunately, it is impossible to know if the tests were done the same way. I really doubt that I was applying a stricter standard than Ted was, so there is a good chance either scanner would be a significant improvement.

I think I am getting about as much out of the Epson 3200 as possible. If you check

http://www.jamesphotography.ca/bakeo...t_results.html

you will see that my contribution was the highest scorer for an Epson 3200.

By the way, I'm well aware of the different factors which can affect one's estimate of performance, including film height. I have done some experiments along those lines with my scanner and I've found the effect is relatively subtle, but it is there.

[Michael Heald]

Hello! Thank you form the link for the scanners. I found the Microtek 5900 on it. The MTF looks good, but it falls way down in chromatic aberration. The optics are problematic; now I know where to expect improvement in when I upgrade. Best regards.

Mike

[Kendrick Pereira]

Question from an ignoramus: Please bear with me.
What do "spi" and "ppi" stand for in scanner-speak? Could someone enlighten me?

[I believe "dpi" stands for "dots per inch"]

[xvvvz]

Maybe others have different definitions, but this is what come to mind for me:
spi = samples per inch
ppi = pixels per inch

You may want to visit Wayne Fulton's www.scantips.com website if you are new to scanning. Great information and tutorials.

Doug
---
www.betterscanning.com

[Leonard Evens]

'spi' is a term introduced, I believe, by Ted harris. It means 'samples per inch'. A flatbed scanner typically collects a horizontal line of samples, stores the results in memory, moves vertically a small amount, collects another horizontal line, etc. The details of how this is done may be more complicated, and there are actually three sets of sensors for each position, providing values for each of the primary colors, R, G, and B. The number of samples taken per inch along each horizontal line is one number and the number of horizontal lines per inch is another number and these are usually given in specifying the scanner resolution, e.g., 3200 x 6400. Usually the smaller number is taken to be 'the resolution'. The measured values are stored in memory as (triplets of) numbers called pixels. Hence the term 'ppi' for 'pixels per inch' is also sometimes used. The term 'dpi' which stands for 'dots per inch' is also commonly used by scanner manufacturers for the same thing, but many people consider it a misnomer. ('Dpi' is also used to describe printer resolution, but in that case, it means something quite different. Relating numbers for digital images from scanners or digital cameras to printer resolution is a bit complicated.)

Digital sampling theory says that if you collect a certain number of samples per uniit length, then the maximal resolution you can achieve in line pairs per unit length is half that. Roughly speaking, you need two pixels for each line pair consisting of a black line and the space next to it. Actual scanners never achieve this theoretcal maximum, but some come closer than others. Usually resolution is measured in 'lp/mm' or 'line pairs per millimeter'. But it could just as well be measured in 'line pairs per inch'. The conversion factor from one to the other is 25.4, which is the exact number of mm in one inch. The Epson 3200 scanner, for example, collects 3200 samples per inch in each horizontal line. That would mean it could at best deliver a resolution of 1600 line pairs per inch, which is the same as about 63 lp/mm. That is the best you could expect to resolve if you took a picture of a resolution test chart with a perfect lens, film capable of infinite resolution, and you scanned it with the Epson 3200. In point of fact, my tests, confirmed by some others, suggest that you can at best do something like 28-30 lp/mm. Translated into inches, that would be be 711 - 762 line pairs per inch. Doubling that, you see that a perfect scanner sampling at 1422 - 1524 samples per inch would give you that. So it would be accurate to say that the Epson 3200 functions like a perfect scanner which samples at aprroximately 1500 spi (or ppi or dpi if you prefer).

The loss of resolution occurs because of faults in the optics and in the scanning hardware. But it is important to remember that the sampling frequency in spi does tell you how many samples will be collected, which will determine the size in pixels of the resulting digital image. For example, my scan region is typically 3.74 x 4.72 inches. So scanning at 3200 dpi yields a digital image of size 3.74 x 3200 by 4.72 x 3200 or about 12,000 x 15,000 pixels. However, the above figures suggest that I won't lose any detail in the image were I to resize that image to about 6,000 x 7,500 pixels. Also, I might do better using a scanner with a lower sampling resolution which had better optics and hence came closer to the theoretical maximum.

[bmarcin]

I have a dumb question. I own a 4990 with SilverFast software. I can see where I can adjust the DPI settings using the Silverfast driver but I don't see any setting options for SPI. From what I understand, I don't believe DPI and SPI are one and the same. With all the talk here about using 2400 SPI, 3200 SPI, could somebody tell me how I would change my SPI settings in Silverfast?

Thanks a lot.

Ben Marcin

[Mike Kovacs]

You certainly did a lot better with your 3200 in the bakeoff than me. Any tricks up your sleave? I've since upgraded to the Doug Fisher holders which are a little better than stock, and let me do my 6x9 MF negs.

I go for a V700 or 4990 just based on digital ICE. I am absolutely fed-up with dust spotting for hours on end with the 3200, compared to my Nikon 35mm scanner...