Image pixels and sizes...

[DennisL]

So, I'm confused...
Say I take a photo (Large, Fine), download to computer then send directly to a printer. They print off a 4x6 paper photograph, have they cropped it?
Or similar for a 5x7 or 8x10? IF they do crop, how do they decide what and where to crop?

Also....

I have this big file sitting on my monitor in Photoshop, if I zoom in to 100% then select the crop tool and make it 4x6, then click, when I print that, is that crop exactly what I'll get?

Thanks!

[baseballboy828]

All common sizes are cropped. They just center crop within the image. Crop it yourself, and the printer won't do any cropping itself.

[porterd2nz]

The first thing to recognise here is that digital cameras take pictures at a different ratio to traditional film cameras. Digital cameras were originally designed to capture images for computer monitors, and as you probably know, these have dimensions typically like 640 x 480 and 800 x 600. If you divide the height by the width, you will find that the ratio is 4:3.

A traditional camera takes pictures that fit perfectly into a 6x4" photo. If you again divide the height by the width, you find that this is a different ratio, 3:2. So what's the problem you ask? Nothing really, but you have a decision to make when you come to print your photos. The standard photo sizes, and frames were designed for film and the 3:2 ratio.

The table below details which commonly available print sizes are best for your images. If you have a digital camera, most probably you will need to choose a print size from the first two columns.

Exact Digital Near Digital Film & 3:2 ratio Digital
6x4.5" 6x4"
5x7"
6x8" 6x9"
8x10" 8x12"


Of course, since the shape of the photo is completely in the hands of the photographer, you can crop to the papers size ratio and have the image appear exactly as you want it to.

[porterd2nz]

Originally Posted by porterd2nz

Exact Digital    Near Digital    Film & 3:2 ratio Digital
6x4.5" 		                                 6x4"
	                 5x7" 	
6x8" 		                                  6x9"
	                 8x10" 	                 8x12"

That table got screwed up. Hopefully this may fix it!?

[jdepould]

The other thing to consider is resolution. Pixels aren't inches. I like the image > image size tool because I can select my DPI and inches for printing and PS handles the pixels.

[Nicole]

Going to move this to post-processing and printing

[Arvid]

Porterd2nz,
I have seen this before and I am still at a loss as to how a ratio of 4:3 is mathematically arrived at from a screen size of 640x480. Dividing 480 by 640 = 0.75. How do I get from 0.75 to 4:3? Likewise, dividing 4 by 6 = 0.6666. How do I get from 0.6666 to a ratio of 3:2? I am sure this will be a “slap my forehead” kind of answer but, I must ask for help no matter how embarrassed I will become.

Thank you
Arvid

[Nicole]

Originally Posted by Arvid

Porterd2nz,
I have seen this before and I am still at a loss as to how a ratio of 4:3 is mathematically arrived at from a screen size of 640x480. Dividing 480 by 640 = 0.75. How do I get from 0.75 to 4:3? Likewise, dividing 4 by 6 = 0.6666. How do I get from 0.6666 to a ratio of 3:2? I am sure this will be a “slap my forehead” kind of answer but, I must ask for help no matter how embarrassed I will become.

Thank you
Arvid

You're putting your ratios backwards

480:640 = .75
3:4 = .75

Same for 4x6... just reverse your ratios so that the smaller number matches the location of the smaller number in both situations.

So, is your forehead red yet?

[baseballboy828]

I won't even go much into telling you what ratios are. Basically the numbers on the left are proportional to those on the right. Dead simple. 640/480=3/2. Most SLR's shoot at around 4x6, perfect for proofs. 8x10's are the format of evil. Since an 8x10 is 5:4 ratio, you crop out a ton. We should switch standards to 4x6, 6x9, 8x12, etc. It would make life so much easier.

[Arvid]

Nicole, sorry but I am still confused. Again, mathematically, how do I get from a ratio of 3:4 to a fraction of .75. Or, vice versa, how do we get from .75 to a ratio of 3:4? I can see what is happening but, I cannot see the numbers required to make the conversion. There must be some formula this.

For example, if by dividing height/width we came up with a fraction of .72 (not that this is or would be an actual figure), how would we arrive at the correct ratio?

This is probably not the time or place to hijack this thread and I apologize to the OP. Nicole, if you want to split this and move it or just drop it, let me know.

Thank you
Arvid