PPI settings in RAW conversion for printing

[Ade H]

I'm a little bit confused by the Pixels Per Inch option in Capture One and how it relates to printing. :confused:

Should I aim to meet the actual dimensions of an A4 print, or leave it at the default 300PPI (which gives 12.96in x 8.64in from my 10.1MP files), or match the PPI to the printer's maximum DPI and let the printer driver enlarge it? How much of a relationship is there between the PPI of a file and a printer's output in DPI?

[Damo77]

At this stage, the resolution you choose is arbitrary and irrelevant. You can set it to your usual output resolution, if that makes things smoother for you.

But of course you can change it later, when you actually come to output. For example, images for web will be 72ppi, and if you're printing on canvas, it might be 150ppi.

I certainly wouldn't worry about trying to achieve perfect A4 at this stage. You can crop/resize later if that's what you need.

[EOS_JD]

For the web, this is not considered "output" and again the ppi is also irrelevant. Web images should be sized in pixels so that they fit on the average screen and are not large enough to allow prints at any decvent quality. Generally 600pixels on the longest edge is a good starting point. ppi can be 1 or 300 or 3000 it won't matter when posing so long as the image is a fixed size in pixels.

Resolution only matters when printing. If you want an A4 image then you should be looking for an image 3508 x 2480 pixels in size. This would give an 11.693" x 8.267" image at 300ppi.

You could instead just resize your image (resample off - 3888 x 2592 pixels image)

This would give an 11.693" x 8.267" image at ppi 313ppi (slight crop involved)

You would not notice any difference.

[Ade H]

So as a general rule, it's better to aim for a physical size that is close to A4, rather than try to make use of the printer's maximum DPI and upscaling abilities.... OK. It's just that the stated dimensions that Capture One and other software provides seem to be somewhat arbitrary in light of printer DPI ratings (the software doesn't know at what DPI you will print; or does it?), so I can't quite see how the two relate or why printers have such high DPI ratings when even professional printing companies have requested only 600DPI images from me in the past. Headline figures I guess!

I'm used to generating images for the web and until recently, printing my own photos has not been on the horizon at all, so I have never given it any thought.

[EOS_JD]

Not at all. Best to size the image a copy of the original) at the size you need to print. If your printer is fairly new, it is likely to have a much higher dpi than your image resolution.

The software will print at the resolution you set it at. Resolution, Print Size and the number of pixels are all inter related. Change one and the other must change (unless you resample - that is add or delete pixels).

Images are measured in Pixels so the resolution of your image is measured in Pixels Per Inch although it does not help that Capture1 and DPP call it DPI (this is WRONG). Photoshop has it right by stating image resolution as ppi (pixels per inch).

DPI however is an output resolution generally a printer.

Your printer lays dots down on paper. The number of dots depends on printer resolution - not image resolution. the two are VERY different - do not confuse them :)

SendGenerally you send your image to the printer at a maximum 300ppi. This is about the highest res you would want to print at. You can in fact send a 150ppi image and get a very acceptable print.

Now you need to set your printer to either highest (or close to highest) quality. My Epson R2400 prints at very high resolutions. I usually set it second top res because there is little difference in using the higher resolution - Highest is 5760 x 1440. Next highest is 2880 x 1440 and this is fine for most images.

Remember you can print your 72ppi 6x4 image at 5760x1440dpi (note the differences) and it'll still look crap. The printer quality will be fine but the printed image will look poor because the image is not a high enough resolution.

Does any of this make sense?

[EOS_JD]

When determining size/resolution I use a simple formula

PS (print Size)
R (Resolution)
Px (Pixels)

PS = R x Px

R = Px/PS

Px = PS x R

Slot in your numbers for any image and you can work out any size/pixel number or resolution.....

OK Your camera gives you images that are 12.96in x 8.64in @ 300ppi

Look at the number of pixels it should be easily calculated....

Px = PS x R (you need to do the calculation for each axis)

Px = 12.96 x 300 = 3888
Px = 8.64 x 300 = 2592

So the image size is 3888 x 2592 (40D size)

Say you want to make a 10 x 8 print at 240 ppi you will therefore know you'll need an image that is 2400px x 1920px.

If you want to find out the resolution you can print out at a 19x13 image at you take the number of Pixels and divide by the PS. Take a 10.1Mp 40D image.

R = Px/PS

R = 3888 / 19 = 204.63
R = 2592 / 13 = 199.38.

In order to print the max print res (without resampling (adding pixels)) would be 199.38ppi.

Let me know if this helps any. It's the same for any image you look at.

[Ade H]

...for the expanded and detailed replies. Very helpful!

My Canon printer is four years old (high-end in its day, but very average now) and it doesn't have DPI settings (just quality settings with no mention of the DPI used).

[EOS_JD]

Your printer WILL have dpi settings. My R2400 has a "best Photo" setting (2880 x 1440) and this isn't actually the best! There's an RPM setting that probvides the top res.

Read the manual of your printer or go to the canon web site for details.

[Ade H]

No, it definitely doesn't have specific control of DPI. I know the printer settings thoroughly and there is only a set of quality stages (draft, standard, high, etc.) The manual fails to mention the DPI settings that are produced by these choices. When doing DTP work, I usually opt for "high" as it's the best available setting. I'll do the same for images, as there isn't much else to change apart from noise reduction and auto-levelling.

[EOS_JD]

i appreciate that it may not mention it but your printer must lay down a certain number of dots to make the print. So that value (not sure where you'll find it) will be an indication of the dpi for the printer. Which one do you have?

I actually have an old Canon printer i850 which was released some 6 years ago and the resolution was 4800 x 1200 dpi. So I'm sure if you dig around you will find the resolution of your current printer.

If your printer is 4 years old it may be around the time the i990 was released? The i990 also has a 4800 x 2400 dpi resolution using 2pl drops of ink, firing through a high density head with 5,376 nozzles.

This info was gained using google so have a search and I'm sure you'll find out more info.

Cheers
JD

[Ade H]

You're not far off! It's an i865, so the max DPI is probably 4800 x 2400, as you say. I just wish that the printer would be more open about what it is using with each setting!

Thanks again for your advice, JD. You have helped two people out with this because a mate of mine had the same question today so I showed him this thread.

[EOS_JD]

Told you so :) Honestly glad to have helped

Check this out

http://www.photo-i.co.uk/Reviews/interactive/Canon%20i865/page_1.htm

Above is a great review of the printer. It is old technology now though and you could do far better with even a cheap canon/epson printer.

The i865 was the replacement to my own model (still in my spare room working) the i850.

Here's the important specification
http://www.photo-i.co.uk/Reviews/interactive/Canon%20i865/page_7.htm

4800 x 1200dpi top resolution - I believe it has a 600 x 600dpi when printing in black though.

Can't seem to find any more info on lesser resolutions when printing colour but I'd take a guess at 2400 x 1200 and 1200 x 600 lowest.