book related question re ppi etc

[back alley]

my lab offers 3 resolutions for scanning-
250 ppi
500ppi
754ppi

i normally get the low res, 250 scans because i use them for posting here and was told that was fine for web use.

now-
for the book...what scan resolution should i have my negs re-scanned at or is the 250 close enough to the required 300ppi?

if i get them scanned at the 500 ppi res, do i then lower the ppi in photo shop after i 'work' on them? (and then save at 300ppi?)

i gotta read a book...soon

joe

 

[Kris]

Joe, if you scan at 300ppi and print at 300dpi, then you get a photo with the size exactly the same as the negative: 24x36mm.

I don't know where this lab get this scanning resolution figures but 250/500/754ppi scan is very low in resolution.

250ppi : 355x236 pixel digital photo
500ppi : 710x472 pixel digital photo
754ppi : 1069x712 pixel digital photo

They are all for web display only!

If you want to make prints, say 4x6 inches, you need 300*4 x 300*6 = 1200x1800 pixel digital photo. That makes scanning resolution 1200/(24/25.4) = 1270 ppi.

24 is the short side of film frame and 25.4 is one inch in mm.

 

[Peter]

If you are using PS, you could push your lower resolution and smaller size picture file by using bicubic interpolation. After enlargement, apply the USM and the result is rather pleasing.

 

[back alley]

hhhmm...maybe i misunderstood them.
they call the levels consumer, pro and expert so they must be better than just low res scans.

i better check with them again tomorrow.

thanks kris,
joe

 

[Kris]

Joe, when you get your film scanned at 250ppi (according to this lab), what's the size of file you get? Not in terms of kilobyte, but in pixel.

 

[back alley]

kris,

if i open the pic in ps and click on image size it looks like this -

pixel dimension 4.56 m

width 1536
height 1038

document size
width 21.333 in.
height 14.417 in.
resolution 72 p/i

 

[Kris]

Looking at pixel dimensions, your film was scanned at around 1100ppi.

1536/(36/25.4) = 1084
1038/(24/25.4) = 1098

Take into account some cropping so the scan doesn't actually cover 36x24mm.

That document size does not have anything to do with scanning resolution. It's to define the ouput. Setting it to 72ppi does not make sense because your monitor resolution isn't 72ppi. You measure the width of your monitor and work out the monitor resolution using the screen resolution setting (800x600, 1024x768, etc).

Example: my monitor width is 11inch (14inch diagonal) and I use 1024x768 setting. That makes my monitor resolution 1024/11=93ppi.

If I have a digital photo with 1024x768, then it will fit perfectly on my screen and I do not have to scroll to view the entire photo.

If I set now to 800x600, my monitor will have 800/11=72ppi resolution. To view 1024x768 photo, I will now need to scroll up/down and sideways to see the entire photo as it won't fit on the monitor.

I hope I made some sense.

 

[Biber]

I think they mean 250/500/754ppi for a 6x4" / 15x10cm print.

 

[back alley]

kinda makes some sense but...

back to my original worry...are my scans, as is, good enough for the book or do they need to be rescanned?

thanks again,
joe

 

[Peter]

Joe, I think they are good enough already. Just use your PS to enhance it as I suggested earlier. 🙂

 

[back alley]

just went to their website and found this, i get the low res called conumer.

Consumer resolution is 1025 x 1536 pixels,
Professional resolution is 2048 x 3072 pixels
Expert resolution is 3023 x 4523 pixels.

 

[Peter]

The photo that is to be published should not be more than 7 inch on the long side.

 

[Kris]

Consumer resolution is 1025 x 1536 pixels,
Professional resolution is 2048 x 3072 pixels
Expert resolution is 3023 x 4523 pixels.

So those Experts are more demanding than the Pros who earn their bread from the photos eh? 🙂

I think it is a good idea to have very high quality scans in case you get your negs scratched later on, or you accidently pour your morning coffee on them, etc IF your wallet can afford it. Depending on how many films you think worth to be archived, it might be cheaper to get a decent film scanner. Something like Scan Dual III or LS-40 maybe? Second hand?

PS: I've never get any of my scans printed. Peter's idea to use PS to upscale your images for 5x7" sounds good to me.

 

[GeneW]

Joe, if we go with 7" @ 300di on the long side of a horizonal image, that's 2100 pixels. Your 1536 pixels should interpolate up without much image degradation. The pro level would be a titch better because you'd be interpolating down.

Joe, can you send me one of your images at the Consumer size?

Send to cdnphoto AT gmail.com

I'll bring it up in Photoshop and check out the details for you and we'll see how it looks.

Gene

 

[rover]

I am going to go through this nightmare next week. I hope you guys can stay patient with us PS challenged folks.

 

[back alley]

gene, the pic has just been emailed to you.

thanks,
joe

 

[GeneW]

gene, the pic has just been emailed to you.

The interpolated image has just been emailed back for you to look at. It required a small sizing up but I think it looks good.

If anyone else needs help with this, email me at cdnfolk AT gmail.com

Gene

 

[back alley]

gene,

got it back and it looks good to me. i trust that going from monitor to page will be an ok journey and it will still look good?

not to get too cocky about all this resolution/pixel stuff but i did what you did while you were doing your thing. i pulled up the pic on ps and changed the res size and long side numbers.

should i be frightened that i'm STARTING (finally) to understand some of this stuff?
of course, i did ask some of the most basic questions here so maybe i'll just go back to humble ignorance.

thanks gene, i appreciate your help, truly.

joe