scanning dpi

[cheewai_m6]

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i've only recently bought myself a film scanner. epson v500. i haven't printed any of my scans yet, but i'm wondering what dpi during scanning is good enough for 5x7 prints? i really only ever print 6x4 but if say i do go to 5x7, what's the dpi you use have scanned at that works fine?

 

i've been scanning some at 3200 dpi and they take quite a while. i've scanned 2400dpi and they are SO much faster to scan, and if that is perfectly fine for up to 5x7, i might just continue to scan at that dpi.

 

also, if it looks perfectly sharp on the monitor at a size which is physically larger than 5x7, does that mean if it's printed out at that size on the monitor, it'd be just as sharp? so i guess i'm saying is, if it's sharp on the monitor, will it be sharp at the same physical size on a print?

[xrogers]

i've only recently bought myself a film scanner. epson v500. i haven't printed any of my scans yet, but i'm wondering what dpi during scanning is good enough for 5x7 prints? i really only ever print 6x4 but if say i do go to 5x7, what's the dpi you use have scanned at that works fine?

 

If you're not too picky, 180dpi of scan per inch of print. Moderately picky, 240, and picky 360 and up. These numbers change a bit depending on your printer, but they're good enough as rules of thumb. Expect your epson to max out around 1800 to 2400 dpi of real resolution (you may have to scan at a higher resolution to get there).

 

i've been scanning some at 3200 dpi and they take quite a while. i've scanned 2400dpi and they are SO much faster to scan, and if that is perfectly fine for up to 5x7, i might just continue to scan at that dpi.

 

I don't expect you'll see a difference to speak of between 2400 and 3200 dpi in a 5x7 print. It's easy to find out, run a quick test. I never scan over 2400 on an epson (but I know some do and claim it's worth it).

 

also, if it looks perfectly sharp on the monitor at a size which is physically larger than 5x7, does that mean if it's printed out at that size on the monitor, it'd be just as sharp? so i guess i'm saying is, if it's sharp on the monitor, will it be sharp at the same physical size on a print?

 

No, it won't be. You need more resolution (at least 2x, some like 4x or more) for a good print than a good display. View at %50 resolution for a reasonable impression of final print look and quality. Don't obsess about sharpness, and keep a steady hand on the unsharp mask---epsons like a lot of it, so you need to use enough, but too much makes ugly, fake looking edges and bad grain.

 

Keep the prints small, and the epson should work just fine.

 

Until later,

 

Clyde

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[adan]

A 35mm frame scanned at 2400 ppi (pixels per inch) is about 8 megapixels. Enlarged to 10" x 15" you'll be able to print at 240 ppi - for 5 x 7 you'll be at about 480 ppi, which is plenty.

 

(There's a fudge factor there, because a 35mm frame is actually a bit smaller than 1" x 1.5" - but close enough)

 

The real question will be if you decide 6 months from now you really want a bigger print - you may have to go back and rescan at 3200. But realistically, as Clyde says, the Epson's lens doesn't resolve much more than 1800 to 2400 lines anyway, no matter how high you set the pixel resolution.

[cheewai_m6]

thanks for the info. helps a lot! i'm not professional, i just really love shooting the m6 and it's a lot more cost effective to scan and process myself. i haven't printed anything bigger than 5x7 ever, cause they're really only for my albums or for a few friends. i purposely didn't buy a higher level scanner knowing i won't need it. but your responses have helped enormously. cause i know now for speed of scanning and quality needed for printing.

[jpattison]

To be correct, don't forget Printer resolution is in DPI (dots per inch), not PPI (pixels per inch)

 

John

[Guest johann_wolfgang]

cheewai_m6,

 

I use the same scanner. A 35 mm frame, scanned at 2400 dpi is good enough for prints up to your expected size. More than 2400 dpi will only make bigger files. You won`t see increasing quality.

 

http://www.l-camera-forum.com/leica-forum/digitale-nachbearbeitung/113742-kannste-mir-mal-einige-dias-scannen.html

 

Just my 5 cents ...

 

Regards

Johann

[too old to care]

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To be correct, don't forget Printer resolution is in DPI (dots per inch), not PPI (pixels per inch)

 

John

 

John, please educate me more on this. My scanner (Canon) does say DPI in its menu, but I always assumed that it was PPI until I read your posting. Now you have me thinking that I may know why my scans are not very good unless I really go up there in DPI, usually 4800 or more. Less than 3200 DPI, even for a 4x6 print, looks bad. My Canon printer uses 8 inks, so I assume that is 8 dots per pixel, right? What does my scanner do? When I scan at 4800 DPI it tells me my file size will be close to 90meg, but when it saves the file it is never more than about 10 meg. However, the photos printed look good but the scan takes 10 minutes or more to do.

 

Thanks, Wayne

[adan]

Basic distinction: "Dots" are the spots of ink a printer or printing press puts on a piece of paper. They are not the same thing as "pixels", which are what make up a digital image file. Take a magnifying glass to a newspaper photo and you will see "ink dots," not pixels - and inkjet dots are just the same, only smaller, and with a more random pattern instead of a halftone grid.

 

Dots per inch (dpi) settings are pretty much hardwired into the printer - there may be a few steps available, from 300 dpi for letters and reports and such, to over 1000 dpi for continuous-tone photographs.

 

Pixels per inch can be anything you set - 247.12 ppi, for example. Pixel resolution has nothing directly to do with printer dot resolution - nor should it.

 

Dots are a solid color of ink. If your printer has 7 inks, each dot can only be one of those 7 colors. Pixels can be any one of 16 million colors. Therefore, to even come close to rendering all of the colors in a photograph, a printer needs a lot of dots for each pixel.

 

E.G. an Epson 3800 lays down 1440 dpi - dots per linear inch - (or about 2 million per square inch). If you print an image at 240 pixels per inch (NOT dots!) the printer will have an array of 6 ink dots x 6 ink dots = 36 possible ink levels (times the number of inks) to render each pixel.

 

Generally, printer software will resample images to a pixel resolution that allows for decent tonalities - substantially below the "dot" resolution. You can send the printer an image at 1440 or 3200 pixels per inch final print resolution if you want - what you will get is more like 240 to 300 pixels per inch on the paper.

 

If you could actually force a printer to print pixels at the same resolution as the ink dots (say, 1440), you'd end up with a very limited color range, because you'd be forcing it to print at a bit depth of one - for each ink you'd get a choice of dot, or no dot - nothing in between. For a 4-ink printer (CMYK), you could have, black, white, cyan, magenta, yellow, red, green and blue. No shades, no hues.

 

(BTW, 1-bit color is how my original Apple IIc drew color on a monitor - and those eight colors were all I could ever see.)

 

That goes up a bit for 6 or 8-ink printers - but still less than 30 reproducable colors. Compared to the 16 million colors available in an 8-bit RGB image. So don't confuse printer dots (dpi) and pixels per inch (ppi) - and pray your printer does not, either.

Edited February 16, 2010 by adan

[jpattison]

Wayne, Andy has explained better than I could, but I'd like to add that printers have their own "native" print resolution, for instance HP is different to Epson..

 

I output from Lightroom at 240dpi ( the program confusingly shows ppi at the Print resolution option!!!) to an HP B9180, and get superb A3+ prints from massive DNG files.

 

Here are some interesting links

 

Inkjet Resolution

 

http://www.mattspinelli.com/ppidpi.html

 

John

Edited February 16, 2010 by jpattison
extra link

[too old to care]

Thanks Andy and John, it makes sense now. I have an M9 on order because I have not been happy with the prints I get with my M6 from local sources, even professional labs. My scans of negatives are not very good, but my slides scan well and look like the original. Even my prints from my 7.5 meg 4/3rds Panasonic look better than either the lab prints or their scans from the negatives of the M6. However, when I do my own printing from my B&W negatives (wet) the prints are great, so I know my lens or camera does not have a problem.

 

Thanks again for the info.

 

Wayne

[Jeff S]

Here's another reference...Basics of Digital Camera Pixels

 

There are many other useful tutorials on this site...for folks like me, who don't know as much as Andy or others.

 

Jeff

[too old to care]

Here's another reference...Basics of Digital Camera Pixels

 

There are many other useful tutorials on this site...for folks like me, who don't know as much as Andy or others.

 

Jeff

 

Although I do use a digital camera some, I am a film buff using mostly 2-1/4s as my standard and my M6 for travel and play, this will be a valuable website to educate myself before my M9 gets here. Thanks for the link Jeff. I just started looking at the other tutorials and they look good.

 

Wayne

[Jeff S]

Wayne, I learned about that site on this forum, too, when I made the transition last year after several decades using film cameras (M6s and M7s as well as slrs, medium and large format).

 

Lots of new things to learn, but I found that my film background using manual cameras (and 4 darkrooms along the way) comes in handy when translating old theory into new. Helps to know, for instance, about bit depth and that the highest "zone" includes half the available information, not evenly spaced. In film, a lot of quality was determined by square inches. Now, it's things like sensor size, bit depth and tonal "smoothness" (no gaps in histogram). Your M9 has all it needs...with your guidance, of course:).

 

The smart folks on these forums (fora), and a few friends, have helped this old dog learn a few new tricks. Be sure to browse the other forums here, e.g., Digital Post Processing Forum, etc. to follow discussions on a multitude of interesting subjects. And, you can always use the search box on the top right to dig up old threads on many subjects.

 

Finally, I highly recommend Sean's site...small fee, but endorsed by many here...not just for equipment reviews and comparisons, but for many insightful essays on a variety of photographic topics, written from the eyes of a practicing photographer...Welcome to ReidReviews

 

Happy shooting, and printing.

 

Jeff

[too old to care]

Thanks Jeff again for the links..

[Jeff S]

Especially for the OP, here's a "sticky" post in the DPP Forum that might be useful...http://www.l-camera-forum.com/leica-forum/digital-post-processing-forum/115989-digital-printing-pixels-resolution-resampling.html

 

Jeff