Cropping to specific Aspect Ratio in PS CS2

04/07/2007 11:33:29 PM · #1

Hi there--

I'm trying to crop a bunch of photos to a specific aspect ratio in Photoshop CS2. I'm using the marquee tool and entering in the fixed aspect ratio. However, about 70% of the time, when I drag a rectangle around the part of the image I wish to keep and then select image - crop, the measurememnts are just slightly off what they should be for the selected aspect ratio.

For example-- I'll open a file and put my aspect ratio as Width 1.5 to Height 1. I'll drag over my image and select crop. However, when I go to resize the image to a format that should work in a 1.5 to 1 aspect ration (like 36in X 24in), I end up with an image that's 36.015in X 24in or something similar.

So then I have to back track, drag the marquee again and, eventually, it does crop correctly and I can get the 36in X 24in photo I need.

It's very frustrating as I have a lot of photos to crop and I need the aspect ratio to be spot on.

Any thoughts out there?

Message edited by author 2007-04-07 23:36:53.

Nikon AF Nikkor 50mm f/1.8D

04/07/2007 11:48:26 PM · #2

Well to follow your words your doing it correctly. But the question is are you actually doing what your saying?

Its a bit odd but yeah 36 x 24 is 1.5:1

David.C

04/07/2007 11:51:43 PM · #3

If you need accuracy, crop in pixels instead of inches. There may be some approximation error from rounding or such that you are running into. Just tell it to make the final image such and such pixels and it will.

David

04/07/2007 11:53:33 PM · #4

Originally posted by David.C:

David is right to the certain extent that Photoshop's math might just be off to a certain degree and its just displaying that side wrong. DO it in pixels then divide the large number by the small.

If it comes out to 1.5 your okay!

04/08/2007 12:01:35 AM · #5

Thanks for the ideas.

I am definitely doing what I said in the first post-- I'm fairly adept at PS.

I'm not cropping in inches or pixels. I'm using the marquee tool and just entering the generic ratio (for example width 1.5 and height 1). I really don't have the time (or math skills, honestly) to take all of my images and figure out what the exact measurements must be for me to get the proper aspect ratio.

When ever I use the marquee tool and crop to a fixed aspect ratio and then try to enlarge to a size that should work, it is definitely off. I did what you suggested and, using pixels, divided the larger size into the smaller. The result was 1.50017636111111111111111111111111111.

Argh!

Nikon AF Nikkor 50mm f/1.8D

04/08/2007 12:04:12 AM · #6

Originally posted by voxpop78:

Well if your comfortable you can email me the file and ill take a look, or atleats give the original dimensions and final dimensions and ill make a test image to work with.

David.C

04/08/2007 12:04:19 AM · #7

Your division goes along with an additional thought I had. It may be the specifying the ratio as 1.5:1 that is causing the trouble. Photoshop uses integer math (no decimals) whenever possible to speed things up, even though it is a bit less accurate.

If you don't want to use pixels, try specifying the ratio as 3:2 instead and see what happens.

David

04/08/2007 12:06:21 AM · #8

Good thought.

04/08/2007 12:14:14 AM · #9

You know I don't think it's the decimal in 1.5.

I just tried a 3:1 aspect ratio. After cropping I should be able to reize to 18in X 6in. Alas, I end up with 18 X 6.002.

Here's an example of a size I'm cropping:

Width = 16.133 in (3872 pixels)
Height = 10.8 in (2592 pixels)
Resolution = 240

The odd thing is that evenually, I can get it to work properly. But it usually takes five or six attempts. I've tried all kinds of different mouse positions when I let up on the drag, thinking that maybe I'm someone moving the selection off just slightly but I can't ever re-create the success or failure. I just keep trying until I get it right.

Odd, huh?

04/08/2007 12:18:09 AM · #10

...

Message edited by author 2007-04-08 00:20:04.

04/08/2007 12:22:10 AM · #11

I made a new image 3872 x 2592

The used the selection tool to crop it to a 1.5:1 or 3:2. Either way my the image was a bit tall.

3872 x 2581

but i checked it and its still not coming out correct.

04/08/2007 12:23:46 AM · #12

Well, at least I have some comfort in knowing that I'm not insane.

;-)

04/08/2007 12:25:00 AM · #13

Originally posted by voxpop78:

Well, at least I have some comfort in knowing that I'm not insane.

;-)

Yeah well this is an odd one.

04/08/2007 12:26:48 AM · #14

Originally posted by voxpop78:

Here's an example of a size I'm cropping:

Width = 16.133 in (3872 pixels)
Height = 10.8 in (2592 pixels)
Resolution = 240

However you said u were trying a 10 x 16?

10 x 16 is 1.6:1

There is a HUGE difference! You can crop by the aspect ratio of the final print size your trying if u want to make it easier.

Message edited by author 2007-04-08 00:28:56.

04/08/2007 12:29:53 AM · #15

I know -- I'm really just trying to crop it to the correct aspect ratio and keep as close to my original dimentions as possible. My lab will do the resizing.

I've only been going to Image- Image Size to double check and make sure that I achieved the correct aspect ratio.

04/08/2007 12:30:23 AM · #16

This is a bit weird though, i took an image croped it to 1.6:1 = work 10 x 16, recropped that to 8x12 worked.

By then weve cut off a couple inches of the photo

04/08/2007 12:31:27 AM · #17

Originally posted by voxpop78:

I have a couple of ideas, if your comfortable id like to try my hand at it but other then that not sure what to tell you.

04/08/2007 12:33:06 AM · #18

Well, what are your ideas?

04/08/2007 12:38:41 AM · #19

Originally posted by voxpop78:

Well, what are your ideas?

well with the odd way i was able to get it perfect by cropping it to 1.6:1 then 1.5:1. We could add some blank area to the canvas just enough to make this possible.

Reason this wont work.... It could be that over a certain resolution Photoshop is actually saying its this size by this size which looks wrong but in reality it isnt.

If your cars gas guage says you have half a tank and you know you filled it up, you would blame the Gas Guage.. its broken. But what if the gas pump didnt actually fill the tank.

What im trying to say is just because photoshop says its 36.015 doesnt mean its that length it might actually be 36 inches. Dont blame the crop, blame the software.

One other thought
Pixel wise the numbers arent even.

your never gonna get an even number by dividing 12 by 10. Hard to explain but your looking for an even number inthe end maybe its not mathmaticly possible.

Let the print lab print it .015 of an inch of the image isnt printed... you wont even notice the loss. Its less then a mm.

Idea 3
Edit it send it to the lab tell them to fix it.

Message edited by author 2007-04-08 00:43:18.

04/08/2007 12:43:06 AM · #20

Given the number of photos I need to crop, adding canvas isn't practical. I'm probably better off using the marquee tool until it works properly.

Thanks for your thoughts. Maybe someone else will read this and have an idea...

04/08/2007 12:45:45 AM · #21

Originally posted by voxpop78:

Well mathmaticly 3872 x2592 pixels is not 1.5:1 so its not photoshop. what side can loss 1 2 or say a few pixels and it be 1.5:1 so how many and which side.

If a picture didnt quite fit in a frame ud just shave the one side not both!

Its still not quite workign though 3872 x 2582 is still short and 3872 x 2581 is a bit over....

Message edited by author 2007-04-08 00:47:29.

04/08/2007 12:45:46 AM · #22

Originally posted by RainMotorsports:

One other thought
Pixel wise the numbers arent even.

your never gonna get an even number by dividing 12 by 10. Hard to explain but your looking for an even number inthe end maybe its not mathmaticly possible.

Let the print lab print it .015 of an inch of the image isnt printed... you wont even notice the loss. Its less then a mm.

Idea 3
Edit it send it to the lab tell them to fix it.

If the image has been cropped to a 1.5:1 aspect ratio, no matter what the image size is, it should be able to be rezied to 36 x 24 or 26x 16 or 6 x 4.

The lab isn't going to print it if it's not at the correct aspect ratio. They won't crop.

Message edited by author 2007-04-08 00:52:23.

04/08/2007 12:48:14 AM · #23

3872 x 2592 is not 1.5:1 we have figured that out already.

04/08/2007 12:49:00 AM · #24

Originally posted by RainMotorsports: