Chart for print size

Photo-gear · Jan 5, 2014

Hi,
I mainly do film photography. I either get prints from my darkroom or from JPEG files. For the last option, I usually get prints with a 800 ppi resolution. In this last case, though, I get results out of trail and error.
What I am looking for is a chart that says what I could get from resolution and prints. In other words, what do I get from 800 ppi and so on.
BTW, could somebody explains to me the difference between PPI and DPI ?

RalphLambrecht · Jan 5, 2014

photo-film said:
Hi,
I mainly do film photography. I either get prints from my darkroom or from JPEG files. For the last option, I usually get prints with a 800 ppi resolution. In this last case, though, I get results out of trail and error.
What I am looking for is a chart that says what I could get from resolution and prints. In other words, what do I get from 800 ppi and so on.
BTW, could somebody explains to me the difference between PPI and DPI ?

PPI ARE ON your monitor or what your scanner and camera does
DPIare what a printer turns them into.

Doyle Thomas · Jan 5, 2014

pixels per inch and dots per inch are interchangeable terms

Alan Klein · Jan 5, 2014

800 ppi seems like a large amount required for print paper. Is that correct?

kintatsu · Jan 6, 2014

photo-film said:
Hi,
I mainly do film photography. I either get prints from my darkroom or from JPEG files. For the last option, I usually get prints with a 800 ppi resolution. In this last case, though, I get results out of trail and error.
What I am looking for is a chart that says what I could get from resolution and prints. In other words, what do I get from 800 ppi and so on.
BTW, could somebody explains to me the difference between PPI and DPI ?

I've found that setting my images to 350dpi, 2048x3072 I get good print quality from my local lab at 8x12. Even with those settings, I can get good quality from MPIX up to 20x30. Remember, viewing distance is part of the calculation for print quality, so 20x30 at 2048x3072 gives you about 100dpi, which is reasonable for about 6 foot viewing distance, although I see good quality at even 2 feet. For 12 inches, 300dpi is reasonable for a 12 inch long side. Anything over that is wasted.

When scanning, 800dpi will give you about about 1800xabout 2400 for MF film scan, which should be ok for about 6x8.

Alan Klein · Jan 6, 2014

The issue is thst most print papers won't provide greater than 300-360 differentiation. So 800 is just wasted. Anyway, it's the overal pixels that you creating. Setting the dpi doesn't mean anything.

kintatsu · Jan 6, 2014

Alan Klein said:
The issue is thst most print papers won't provide greater than 300-360 differentiation. So 800 is just wasted. Anyway, it's the overal pixels that you creating. Setting the dpi doesn't mean anything.

Forgive me disagreeing on the last part. Setting the DPI determines your output size to some degree. For instance, a desired viewing distance of 12 inches would require 300 dpi. If you wish to view a 4x6 at 12 inches, it should be 1200x1800. A 10x15 inches at the same distance requires 3000x4500, or about 13.5 megapixels. a 10x15 usually doesn't get viewed that closely, so 150-200 dpi is usually sufficient. The 300 dpi is the benchmark for the 12 inch viewing distance to be clear, sharp, and properly viewed from that distance. anything less loses detail, sharpness, and even contrast at that distance.

Alan Klein · Mar 8, 2014

Ok I;m confused. If the benchmark is to lay down 300dpi onto the paper, why do printers provide 1200dpi and up?

xtolsniffer · Mar 8, 2014

I made myself a little excel spreadsheet to do this. Just feed in your required output print size and the print ppi and it's easy to calculate the required scan resolution (in pixels per inch) to get the output. The pro lab I use has Fuji Frontier printers that print at 254 dpi, so I scan negatives and slides at the right resolution to fit into the size of print I want. So for example if I have a 35mm slide, which is 1.42x0.94 inches, and I want a 7.5x5" print, I know the output resolution on the Fuji frontier (for this lab) is 254 dpi, so I need to scan at around (7.5x254)/1.42 = 1344 ppi and (5.5x254)/0.94 = 1344 ppi.

The differences between dpi and ppi are easy to get mixed up with, inkjets may have very high dpi settings, but that's just the number of dots they lay down her inch. If you have a 100 ppi image, and a 600 dpi printer, it will just lay down six dots per pixel on the paper.

Alan Klein · Mar 8, 2014

I scan at 2400dpi regardless of the final print size. That way I only have to edit once. What advantages are there in canning at smaller resolution sizes?

xtolsniffer · Mar 8, 2014

Only that I get smaller file sizes that I upload to their server. They do ask for 254 ppi at the final print size which is what I do as per their instructions:

Photos from Digital Media

I could obviously scan at higher res and then let them do the downsampling, or I could scan at higher res and do the downsampling myself, but it's a habit I've just got into. Their results are great so I just stick to a formula that works for me

ctscanner · Mar 8, 2014

Xtolsniffer.

Regarding your posting today. I would suggest another alternative - that being don't throw away information which is what you're doing by reducing your scan size to agree with what the printer wants. Why not scan at the maximum PPI (or DPI - it doesn't make any difference), do whatever corrections you need to the image and save it as a Master. When it comes time to print, save the Master under another name - make whatever changes you might including resizing the image, and you're good to go - and your original scan is still available for whatever you might want to do in the future.

Just a thought,

Ctscanner

lenny · Mar 12, 2014

ppi and dpi can be deceptive. Look at the Image size dialog. it will tell you how many total pixels you have. Generally, it comes up with the image sized at whatever the original neg was. Just change the print size to 10, or 20 inches and you will see what your result is...

If you have 10,000 total pixels an you want to make a 10 inch print, then the resulting dpi will be 1,000. If you have a total of 800 pixels then a 10 inch print will be at 80 dpi (pretty lousy). If it really is 800 ppi and its a 2.25 inch neg, then it would be (800 x 2.25), or 1800 total pixels. a 10 inch print would be 180 dpi. A 20 inch print would be 90 dpi, very lousy, artifacts, etc.

This is why I don't do prices by megabyte, I just give everyone the whole shootin' match.... 800 sounds like a lot, but it isn't... especially given that most people want to be able to make a 16x20, of not now, then later, if they choose to.

Lenny

Prof_Pixel · Aug 16, 2014

photo-film said:
BTW, could somebody explains to me the difference between PPI and DPI ?

PPI equals pixels per inch and that's pretty clear. It's DPI that causes the confusion (and has since the first days of digital imaging). DPI means DOTS per inch and was used both for pixels and dots of ink (that varied by size) used in printing (for example, some early Epson printers were listed as 300 DPI, but the 'dots' were not pixels; many dots were printed to produce each pixel) When I traveled making presentations on digital imaging for Kodak in the late '80s and early '90s, I used to always try and get people to use ppi and not dpi for digital images, but realized I was fighting a loosing battle. FWIW, I always try to use ppi when talking about digital images.

Chart for print size

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