what resolution for medium fornat negatives

Hi

I'm starting to scan my medium format negatives but i'm with serious doubt!

I use an Epson 4990 scanner wich they marketing with a 4800 dpi resolution.
My intention is to print the imagens and i'm using the Epson software.

1) Do i use the maximum 4800 dpi resolution told by Epson and then resize in a photo editor for another resolution? And what resolution?

2) Do i scan them on a lower resolution ( 3200 dpi) and then resize?

3) There is no problem to scan the negatives with a interpolated resolution and Then resize?

4) Or is it better to scan on the real resolution and Then resize?

5) Does anybody knows the real resolution for This scanner?

6) What is the best workflow to scan medium format negatives in terms of resolution?

I do know that This is not a prime scanner and a Nikon 9000 scanner or an Hasseblad flexlight scanner can produce real good scans...but the 4990 as to be right now the One!

Thank you in advance
All the best

assuming you are scanning for print the resolution should be a multiple of your printer resolution 300 or 360 dpi. the 4900 is probly 1200 optical(im not sure). I scan everything with my 1680 at the max optical resolution (1600) and resize without resample in PS to 720 letting the dimisions go where they may. this becomes my working file which i can then resize to what ever my print needs may be using Perfect Resize from ONONE softwear. Perfect Resize converts the file to a vector then resizes and rastorizes. if you use PS you will get a better result doing the resize is small doses say about 20% at a time.

Scan at the highest true optical resolution for your scanner to create a master file and then do any downsizing later in Photoshop. I would do a test scan at 2400 ppi and 3200 ppi to see if 3200 ppi gives you any advantage. If 3200 doesn't give any advantage, go with 2400 ppi.

Doug

Hi Doug,

My trouble is it to know what is the true optical resolution. Epson says 4800ppi, tests from people (searched on different sites) says that the true optical resolution is around 1200ppi. So..what should i do? Also using 4800dpi is not going to interpolate the pixels?

Thanks

The true optical resolution is a function of the lens and how well your scanning height correlates to the focus height of your particular scanner. I suggest you buy one of Doug's fantastic custom film holders and spend and hour or so setting it to the correct height. Only then will you be able to determine the true performance of your scanner (for what it's worth, 1200ppi sounds a bit low to me).

the optical res on the 4900 is 1200x2400, what this means is that on the short dimision the res is 1200 and on the long dimision 2400. the reason fot the difference is that the lead screw is moving at 1/2 the pixel dimision as it captures the image. if you scan at 2400 the scanner will extrapolate the short dimision. i say extrapolate rather than interpolate because the scanner is not interpeting the surrounding pixels and making a decision about what values to assign to a new pixel. it simply adds a pixel with the same value ajacent to the optically scaned pixel. scanning at 1200 is recommened (max optical) as stated above

I'll resurrect this thread with a related question. I recently acquired a very inexpensive, used Epson 4870 flatbed scanner; its a few generations old, but still has credible specs. Primarily so I can scan 4x5 negatives, but it will occasionally used for 35mm and medium format (I also have a Coolscan V and an Epson V600 at another location). It has an optical resolution of 4800 dpi.

With negatives I feel are worth the effort, I want to scan for future printing on both quality home photo printers (like my Canon Pro-100) and "pro" level printers (such as an Epson 7990). I would expect the absolute max print size for 35mm to be 16x20 (and more likely 11x14) and the max print size for larger formats to be 20x24 (and more likely 16x20).

Obviously I could scan all film formats at 4800 dpi, but that will result in very large files for MF and especially 4x5. So my thought is to scan 35mm at 4800, MF at 3200 and 4x5 at 2400. I will be saving as TIFF files. That will yield file sizes ranging from approximately 50mb for 35mm and 220mb for 4x5 at 16-bit greyscale.

Does this sound reasonable? Is 3200 and 2400 overkill for MF and 4x5 (respectively)?

I've got the 4870. In my testing I never found any benefit to scanning over 2400ppi, and I think the real resolution to be closer to 2200ppi. 4800ppi does not resolve any more information over 2400ppi on my scanner so I scan everything at 2400. I have better scanners which I use for the smaller formats. At those resolutions you can get a very good 7x10 from 35mm film (360ppi on Epsons, which can usually show a slight improvement at 720ppi). At normal viewing distances an 11x14 also looks decent, but that's as large as I'd go from 35mm.

Why shoot larger format if you're going to scan at reduced resolution? You're wasting all that real estate. Scan all format at the highest resolution you can scan at that works. Larry's 2400 is a good setting.

I would scan at 3200 ppi until you have confirmed you cannot gain anything over 2400 ppi. Get your film as flat as possible and test to see if you need to raise your holders to see if you can gan some sharpness that way. Finally, as old as that scanner is, you should open it up and carefully clean the underside of the glass because by now to some extent there will be a coating on the underside of the glass. With doing these things, you very likely will see a small gain over 2400 ppi if your scanner is still in good working order. Every little bit of resolution makes a difference once you start post processing.

Here are some links I put up for opening up scanners. There are lots more on the net and youtube:
http://www.betterscanning.com/scanning/dismantling.html

Doug