Photoshop: Image Size not proportionate?

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  • Updated 1 year ago
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I might've misunderstood how the 'image size' function is supposed to work, but I feel like I'm going crazy so please bear with me.

I'm getting an image ready for printing.
It's in A3 size on Photoshop (so 29.7 x 42 cm)
What I've been trying to do, is add a 3cm border by increasing the size of both height and width in 'canvas size' by 3cm each.
Cool, I end up with a white 3cm border all around. It's A3 plus 3cm on each side.

Now I want to get it back down to A3 size including the border, so a logical step would be to just go to image size and change one of the values to 29.7 or 42 in cm and that's it right?
Well apparently not, because when I change one value to size it down, the final result is not A3 size e.g. If I change width to 29.7, height gets automatically set to 40.87cm rather than 42... 
Why does that happen if the length I added to both sides is the same??
I know I can change them both manually but then my image becomes skewed.
But I don't understand why considering that I added the same value to both sides...

I'm not sure if I'm just stupid or if there's some fault at play.

Thanks!
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Nick

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Posted 1 year ago

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Joe Creative

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Question one. Are you running g the new CC? If so, the new constrain proportion that everyone hates might be the issue . Everyone has asked Adobe to take that option off. No one likes it. You might need to go down a CC: 2018 to accomplish the resize that you wish to do. Everyone loves and hate the new Photoshop. We are all waiting on the update to turn on Or off constraint proportion.
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Steve Kenny

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I couldn't wrap my 2 brain cells around this same situation the first time I attempted something similar.
But, the problem is that the fact that by adding the same border all around, you do not end up with the proper ratio (A3 in your case) so you cannot resize your image to such.
As for a fix/work-around, we will have to wait for someone else for that, I have yet to find one. :(
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TangCanada

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Like Steve says your ratio will be off if you add 3cm all around and then resize down having the width and height linked.
Just delink the width/height and resize down by 3cm each.



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Yves Crausaz

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Hello,
The ratio 420mm / 297mm = 1.414141414141414
The ratio (420mm + 60mm) / (297mm + 60mm) = 1.34453781512605
a difference between the ratios of -0.069603599015364

The reports are not the same, you can never reduce the image so that the sides decrease in the same proportion using these 2 functions of Photoshop!

It is mathematically impossible the two ratios must be identical to be able to reduce also!






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Johan Elzenga, Champion

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If you don’t want to distort the image, then what you need to do is the following:
1: Resize the image, so that the longest side becomes 6cm smaller
2: The shortest side will become smaller too, but not by 6cm. Crop it (or use Canvas Size) to correct for that.
3: Now both sides are 6cm smaller, so now you can add a 3cm border on all sides.
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TangCanada

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@Johan
Wont you end up with an image that is not scaled to A3?
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Johan Elzenga, Champion

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You need to start with an image that is already scaled to A3 (and that is what the OP does).
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TangCanada

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Sry, but I am sure I am missing something relative to the end result scale.

I am really not sure if the question was answered :
"Wont you end up with an image that is not scaled to A3?"

If 6cm is taken off from both the long side and the short side how can you still retain the same A3 scale? (confused)



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Johan Elzenga, Champion

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You forget something. 6 cm is taken off, but then the same 6 cm is added again (by adding 3 cm borders on all four sides). Adding borders is the whole point of doing this.
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Steve Kenny

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By adjusting the long size down (by any amount), the only way to maintain the original ratio is to crop off (from the short side) some of the original image. I am not sure that the OP really wants this...?
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Johan Elzenga, Champion

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I don’t think the OP has much choice. It is either that, or he will have to distort the image.