Scan Resolution?

[Scott --]

Hey, everyone -

I actually managed (somehow, despite my usual ineptitude) to make a possible sale today. Client's requesting a "high resolution scan", which he defines as 300 dpi at 8-1/2 x 11".

Ok, so if I go into VueScan, select "Scan Resolution: 300 dpi" and go to "Output Size: 8.5 x 11", am I getting what's being asked for? I generally scan at the scanner's max (1200 dpi for my crap-cheapo flatbed) and resize in PhotoShop. And, clearly, I should/will clarify with the client what exactly he needs (and, should my scanner not generate what's needed, they'll scan the slide, anyway), but I'd like to get a handle on this tonight before I make a fool of myself tomorrow. Which is inevitable, anyway, but still...

Any advice?

Thanks,
Scott

[Eric James]

I would scan at max res and then resize in PS using the crop tool set to the client's desired dimensions and resolution. The "scan once" or "master scan" workflow philosophy is a big time saver and saves wear and tear on your equipment and slides/negs. Some scanners don't provide equivalent output quality at all resolution settings; it's a good bet that your scanner performs well at it's maximum scanning resolution.

Congratulations on your sale.

[Gene McCluney]

I will second the above recommendations. The ONLY time I scan at less than maximum resolution of my scanners is when scanning a 4x5 or 8x10 negative, when full optical resolution of the scanner is overkill, and time consuming.

[Ted Harris]

Scott, is it a 35mm slide that you are being asked to scan, if so does your potential client understand that even the best of the current generation of consumer flatbed scanners doesn't do much of a job on a 35mm slide? You can save both of you a lot of grief if he understands that.

Having said that, the earlier advice is correct. Scan at the maximum real resolution of the scanner and then down rez in PS. The technique to use in PS is to go to Image>Image Size. Next uncheck the "Resample Image" box to maintain the size of the file. Then set the image size.

[JW Dewdney]

I will second the above recommendations. The ONLY time I scan at less than maximum resolution of my scanners is when scanning a 4x5 or 8x10 negative, when full optical resolution of the scanner is overkill, and time consuming.

Okay - sorry Gene - not that it's relevant to the conversation - but that just didn't make ANY sense to me. You use FULL optical res when scanning printed materials (which generally don't need any more than 300ppi) - yet when it comes to scanning FILM - which has alot more than 300ppi to OFFER - that's when you DON'T??

Could you have had them reversed?

[Gene McCluney]

Okay - sorry Gene - not that it's relevant to the conversation - but that just didn't make ANY sense to me. You use FULL optical res when scanning printed materials (which generally don't need any more than 300ppi) - yet when it comes to scanning FILM - which has alot more than 300ppi to OFFER - that's when you DON'T??

Could you have had them reversed?

I didn't put printed materials in my equation. What I meant to say was any film below 4x5 in size, I use full optical resolution of my scanners, which is 4000ppi. For 4x5 I often use 1250ppi, out of 2500ppi available to me. For 8x10, for convenience I use 600ppi frequently, as even that makes a 16x20 300ppi print. There, is that clear? Now, for reflected (print) material, I scan at whatever resolution will result in the final reproduction size requested by my clients.

[Ted Harris]

Gene, what you ar doing may or may not make sense depending on th scanner you are using. Point being that the full advertised optical resolution of all of the consumer flatbed scanners is total marketing hype and th real optical resolution is in the range of 2000 to 2400 spi for all of the current models, much lower if we are talking older scanners. If you are using a high end scanner then it might make sense.

[Scott --]

Thanks for the input, guys.

Specifically, I'm scanning a 4x5 Provia transparency on an old HP 5370C Scanjet flatbed with transparency adapter and VueScan. It's not the best, and I don't know if I can coax something worthwhile out of it; like I said, I'll get the best I can together, forward it on, and if it's not going to cut it, they can drum scan the slide. Which is what'll likely happen, but if there's a way to expidite handling on this (which a digital file would obviously do), then I want to give it a shot.

Looks like I'll scan it at the max optical, maybe a little higher, then downsample it in PS to the requested 300 dpi. Sound right? And I'm guessing I should be working at 48 bit color instead of 24...

So much easier just scanning for web use, I tell ya.

[JavaDuke]

Scott,

Don't scan higher, just use the native optical resolution of the scanner. Resampling algorithms of Photoshop are way better than any scanner firmware or scanning software. For example, if your native scanner res is 2500 dpi, scan at this resolution, then open the file in Photoshop, open the Image Size dialog and resample your image to the required size and resolution. Some people recommend downsampling the image with lots of fine details gradually, while some are ok with doing it in one step. I think in your case it's ok to do it in one step, since your print will be only 8.5 x 11".
Hope this helps.

P.S. Oh, and yes, 48 bit color (i.e. 16-bit) Adobe RGB. You can convert it to 8 bit sRGB last step before you send it to the printer.

[Scott --]

Ok, got a decent scan at the max native resolution (1200 ppi), sized to a bit more than 8-1/2 x 11 to cover the aspect ratio. Downsampled it in PhotoShop, and the image looks nice. Have run off a slew of format and USM questions to the publisher (essentially confirming that they'll want the raw scan film at their requested resolution, vs. me doing any USM or anything). We'll see what happens.

Thanks for all the input.
Scott