Regaring photo size VS. pixel size

[emillu]

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Hello Pros,

 

After taking thousands of shots, sometimes i am thinking about printing them out in small/ large size photo just to feel the moment. I wonder what would be the best pixel size to save the file to product the best quality?

 

What would be the BEST pixel size to produce: (dimensions in inch)

 

4x6

5x7

10x12 photos?

 

I know that these dimensions are landscape photo dimensions, what about the dimensions for portrait and the equivalent pixel size?

 

Also, what type of PS CS5 settings has to be done in order to produce the best jpeg output image quality?

 

 

Thanks for the help!

All the best!

[wparsonsgisnet]

Would you specify how you are printing? That is, are you printing from Photoshop?

 

You never have a problem if you have more than enough pixels to print. In Photoshop, if you specify the image size and the PPI, Photoshop will show you if you have a problem by changing one of these parameters.

 

If you don't have enough pixels, just uprez the image so you can print the desired size.

 

With regard to "Best number of pixels," I shoot raw, thereby getting the maximum number of pixels to begin with. This only causes storage problems. Then, cropping gives whatever pixels remain. If it's not enough, uprez. Again, PS will tell you when there is a conflict in the image size dialog.

[ho_co]

Just putting into other words the same thing as Wilson said: If you're in Photoshop, don't worry about the pixel count.

 

Whatever size you want to print at, the print module in Photoshop will handle the pixel count itself automatically.

 

That is, if I've got a 3968 x 2232 image, I can simply pick "Page Setup..." and tell the program what size paper is loaded in the printer (4 x 6, 8.5 x 11, etc).

 

Then when I choose "Print...," Photoshop illustrates how it will print the image. It'll probably overhang the paper edges, in which case I can click "Scale to fit media" to let PS downsize automatically while printing.

 

That way you don't make any changes to your original and can still use it later for larger or smaller prints. Remember, each time you modify a file, you run the risk of losing information.

 

 

You're probably already aware of that, in which case I'll now bow out, because you're asking a question at a higher level than I can respond to.

[emillu]

Hi Bill,

 

Thanks for the quick response!

Yes, in terms of printing, i will be printing photos either straight from photoshop or work out my printing size from photoshop then save a file to print later on.

 

I understand that there is a minimum pixel required to print a photo in certain size. If the pixel is lower than the minimum pixel, it reduces the clarity of the image.

 

for example,

 

To print a size 5x7 photo, we need a minimum pixel of 1500 x 2100 (5x300dp, 7x300dpi) to produce good quality print.

 

I guess my question really comes to the point that if we have our pixels greater than 1500 x 2100 to print out. Can we really see the quality difference in our naked eyes?

[emillu]

Thanks Howard,

 

At the end I guess there is no BEST pixel size to print 4x6, 5x7, 10x12...etc. photos.

Only minimum/suggested pixel size to print without seeing large pixels on the image!

 

Large pixel size are only for retouching.........3600x5400 pixels probably won't give us a better image quality compare to 1500x2100 if to print 5x7 inch size photos?

[ho_co]

Ayyy! You've gone beyond my competence, as I was afraid. But why should that stop me?

 

There are a number of printing threads on the forum. One group of people (with Epson printers) will tell you there's an optimum number of DPI to use to match the printer's native capability; the other group (maybe with other brands and/or later Epsons?) say that's hogwash. So does a recent Ctein article on TOP. However, people who understand the argument tell me when I say that, I don't understand the issue, and on this one I'm happy to agree with them.

 

Possibly on topic: I think what you may be wanting to ask about is the number of Dots Per Inch for a given size print rather than actual number of pixels.

 

To which question my understanding is that ca 300-600 dpi is good for big prints, 200-240 dpi for, say, 5x7 to 11x14, and fewer, maybe 150-200, for 4x6 etc.

 

 

I know how upsetting it can be for someone to run on answering a question that hasn't been asked, and I hope my responses fit somewhat what you're asking.

 

 

I think you're on track, except that the computer will do the computation once you choose dpi. That is, there's generally no need to reduce the number of pixels just to print smaller. If I understand correctly: If I print my 3968 x 2232 image on 4x6 inch paper at 500 dpi, I'll be using a lot of ink that I didn't need for that small a print. But instead of changing my image's pixel count, I can just reduce the printer's dpi to 100 to 180 for the small paper. I don't need to change pixel count, just dots per inch.

 

Someone else can say this better than I. Have you checked out http://www.l-camera-forum.com/leica-forum/digital-post-processing-forum/115989-digital-printing-pixels-resolution-resampling.html? It may address what you're asking.

[adan]

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Let me toss a few monkey wrenches into this discussion.

 

First - forget "300 ppi" times the image size. The recommendation for 300 pixels per inch was developed for magazine reproduction, on the theory that high-end magazines that print with 150-line halftone screens need 2 pixels per line to avoid possible aliasing, and to provide suitable tonal data. Thanks to the internet's tendency to spread and replicate half-truths, it has been applied to inkjet printing, where it is really not appropriate.

 

I'll avoid the messy details unless someone wants them, but inkjet printers just use a very different method of creating tonality from dots of solid ink colors than printing presses.

 

Realistically, their linear resolution is about 240 lines per inch, and the printing software automatically resamples the image to that resolution. So it doesn't matter if you send it 300 ppi or 600 ppi or 180 ppi - it will PRINT 240 ppi.

 

There are, in fact, downsides to sending a printer more pixels than its native resolution.

 

First, details you can see on your screen in the full-sized image at 100% zoom will simply - disappear - when the file is printed at substantially more than 240 ppi. Downsampled out of existence. I just made a A2 print (20" x 14") from a file that, at that size, was about 267 ppi native resolution. And some of the pixel-level details visible on-screen were already being downsampled out of existence with just that small change from "native" 267 to the printer's 240.

 

(Yes, manual downsampling wil also make those details vanish - but at least I know what I'm going to get before spending cash on ink and paper. And can maybe adjust my sharpening ahead of printing to restore some detail)

 

Secondly, things like sharpening filters are applied to your original pixels as a function of pixel size, and that sharpening may also be wiped out if the image is being downsampled after the fact (i.e. on the way down the cable to the printer).

 

Again, I ran a series of tests with an M9 image printed on letter-size paper - full resolution, and also downsampled a priori to various resolutions, with varying levels of sharpening. The sharpest-LOOKING print was from an image downsampled by me to 240 ppi, and then USM'd at .5-pixel radius and 200%. The prints made at the M9's native resolution, which worked out to about 470 ppi, actually looked LESS crisp and sharp printed at that size.

 

I'm finding the same is true, by analogy, producing the .pdf files for my online magazine. The "auto" downsampling done to images in the pdf-export process does not include appropriate sharpening, so I get more "apparent" sharpness by doing my own downsampling BEFORE doing the sharpening, and then using the image "tuned" for on-screen viewing. Which is kind of a headache, since I don't know the "final" image size until I have finished the design - but has to be done or the results are too soft.

 

Now, for rough-and-ready printing of family snapshots at 4 x 6, the differences may be pretty small and not worth the extra steps. But for exhibition prints, I've done the tests and seen the results - and I do my own downsampling rather than leave it to the printer software.

[wparsonsgisnet]

The "thank you" is not enuf for me. Andy's post is the reason I lurk here.

 

Thanks for that lucid explanation.

[rob_x2004]

Let me toss a few monkey wrenches into this discussion.

Whats your coment on upsampling simply using modern printer softwares?

Ive sent 250 to 450kb files off that raised all the alarms yet came back crisper clearer and definition leagues ahead of 5Mb files that werent edited properly.

I often see poorly exposed images with blown highlights and out of focus area blobs that have colour layed down by printer algorithms that cover a multitude of sins and save the day.

Why not work in an image file size you can edit properly and where you can adequately assess 100%, allow the printer to uprez, and if that isnt good enough, run to QImage or genuine fractals?

Dont get me wrong, I 'think' in print I can see a slighty better print in 5400ppi 16x scan, but I know what it is, no one else can pick it.