Explaining Low Res and High Res Photos and Prints

[rockstarsmasher]

I'm very confused about what the whole converting a high res image to a low res such has from 300pp to 72ppi or reversed from 240ppi to 300ppi?

I shot an image with my 5d Mark2 in RAW and opened it with Adobe Camera Raw.

Can someone explain the process of making it into a high resolution image?

Does it matter when you go to 'image size' in Photoshop and change the resolution to 300pp?

Or does only the amount of pixels (Length and Width) that the image has matter that determines if its high resolution or not?

How big can I print an image at the suggested 300 megapixels?

Can someone explain step by step?

Thanks!

 

[iDad]

If your Document is a certain size 300 that's great you can print it no problem but once you start increasing the size of the document and spreading out the pixels to accommodate the increased area detail is going to start to lose shrapness so if you plan on printing larger you're better off creating the document larger(higher res) then needed at the moment. illustrator will not have that problem you can resize Till the cows come home

 

[Tom Mann]

There are two very different and equally valid meanings to the term, "resolution", as applied to digital images:

#1) "Resolution" is the dimensions of the image in pixels.

#2) "Resolution" is the number of pixels per inch (on a display) or dots per inch (when printed).

The amount of confusion caused by having two meanings for the same term is unbelievable.

Resolution #1 tells you the amount of information contained in an image, no matter whether it is on a tiny screen or spread out over a poster-sized print. #1 can't be increased without asking your software to guess at the new information (RGB values of pixels) that didn't formerly exist. This is what happens when you check the "resample" box in the "image size" command in PS.

Increasing the number of pixels is commonly called, "up-rez'ing" and decreasing the number of pixels, "down-rez'ing".

Resolution #2 simply tells you how far apart the pixels are going to be when you display them, or how far apart the dots are going to be when you print them. Changing Resolution #2 (ppi / dpi) without changing Resolution #1 (pixel dimensions) means that the final image is going to change its real-world, physical size, but no new information (new pixels) is created. This is what happens if you don't check the "resample" box in the "image size"command of PS.

The minimum acceptable value of Resolution #2 (ie, ppi/dpi) depends on how closely you are going to examine the image. Specifically, you can get away with much lower dpi/ppi for a billboard (always viewed fro more than 100 feet away) compared to a small print in a gallery where everyone's nose is going to be a couple of inches away from the print.

The pixel dimensions, ppi and size are related by a simple formula: #pixels = (#pixels per inch) * (# of inches). Photoshop conveniently takes care of these conversions in it's "image size" dialog box, constraining you to manipulate numbers only in the correct fields depending on whether or not you have the "resample" option checked.

HTH,

Tom M

 

[iDad]

Couldn't have said it better myself.......DOHyouBthesplainmachine mon! Are you related to Webster by chance? :mrgreen:

 

[ALB68]

I am going to try and add something to this without inserting my foot into my mouth in the presence of these two graphics policemen. i.e. Chief Tom and Captain iDad.
Since your opening your images in Adobe Camera Raw to begin with and you know your going to print them, set ACR (click the info text at the bottom and it will open the work flow options window) to 300. You can also set your color space, which for print I set Adobe 1998 and your sharpening type (screen, glossy paper etc.).

Now, my camera is little puny 6 Megapixels compared to the 21 MP Canon you have, so what you begin with is going to depend on what size you set in the camera to shoot the photo. My max is going to be 3008 x 2000 ppi, which at 300 ppi is a shade over 10" wide and 6.67 " high. So, I have no problem with the image fitting my paper printed in landscape orientation as is. Your output could be 3 or 4 times my size, so it's going to depend on how you go about planning your end use. Keeping in mind of course that you can resize the photo in PS will dictate what you do. You may want to make a big huge print and then size it down to hand out for wallet size, so I always go bigger than I need and size down. You can size down without degradation of your image in most cases. Trouble usually starts with trying to upsize. All of this manipulation takes place in the Image/Image Size window in PS. Best to just open the image and experiment by changing your pixel dimensions or in inches and see how your ppi changes accordingly. You'll get the hang of it by working with it. Good luck.