which proportion is correct? -- of headshots and pixel aspect ratio

[alisonl0shi]

My question is, if you get a headshot image of a person, that person looks wider if you "view pixel aspect correction" and skinnier if you just look at it the way it's being displayed on screen (opened n PS). Which one is correct? Or does it automatically correct itself when you import it into an ID picture box?

Thanks so much --

[davescm]

Pixel aspect ratio correction is for some video formats which use none square pixels, and would display incorrectly if square pixels were used. It has nothing to do with horizontal and upright images.

For normal photographic images leave pixel aspect as square and pixel aspect ratio correction off.

Dave

[alisonl0shi]

Thank you. I should have been more specific -- since I'm still a little confused though. If the image *comes* with a non-square ratio, (in other words, when you open it up the first time you get the message that the "pixel aspect ratio correction is for preview purposes "  but for a higher quality image you should turn it off ... what do they mean by "preview"? What *isn't* a preview?  Is preview what you see in an ID picture box?  Or is it the icon on the screen when you are looking for the file? But the file you are actually looking at on screen is NOT the preview? In other words, the "preview" will be the fatter one (in this case)? And when you turn off the correction, the preview and the image you see on screen will then match?

Sorry, I guess my confusion s that I really don't know what "preview" means except that it might be what ID puts in your picture box to tell you that the file is there.

[davescm]

OK - I'm not sure where you have got an image with non square pixels (unless it was from a video) but regardless :

In Photoshop we normally check our images at 100% zoom. This means that 1 image pixel maps onto 1 screen pixel and we can check blending and sharpening are applied correctly.

With an image that uses none square pixels then the mapping of image to screen pixels cannot be 1 to 1 unless you turn the pixel aspect ratio correction off. Then it will be mapped 1 to 1 for checking the image at 100% zoom  but will of course be distorted. So for checking the blending and sharpening - switch it off and view at 100%. For all other image use and viewing - leave it on so that the height to width ratio is shown correctly.

Dave

[alisonl0shi]

So ... that means that preview *is* the image that I'm seeing on screen? And that the correct "look" is the skinnier person. OK. Thank you.

Is there a way I could resample the image so that the image was correct-looking (skinnier) when the pixels were square?

[alisonl0shi]

The reason I'm asking is that when I look at the ID file "preview" and compare it with the actual photoshop file with "pixel aspect ratio correction" *checked*, they are of different proportions. The ID file version is fat, and the photoshop file thin. But they are the same file. So, it looks to me as if the "thin" view doesn't translate into ID. Aaargh.

[davescm]

Can you put up a link to the file (e.g. drop box or similar).

Dave

[alisonl0shi]

Yes --- here:

Dropbox - sample file.tif

I blurred and posterized the poor fellow, but the problem should still be apparent.

[davescm]

Hi

The link you sent has a pixel aspect ratio of 0.972 - you can see that by checking Pixel Aspect Ratio Custom

To get rid of that and go back to square pixels do the following.

1. Turn off pixel aspect ratio correction

2. Go to pixel aspect ratio and set it to square.

3 Go to image size and uncheck the lock symbol. then set width to 97.2% and height to 100% . Ensure resample is checked and press OK

You know have a square pixel image to use

Dave

[alisonl0shi]

Now I realize I was confused, in my original post. If you view with "pixel aspect ratio correction" *checked*, then the person looks skinnier. If you uncheck it he looks fatter. So the post should have read ...

"that person looks wider if you turn off "view pixel aspect correction" and skinnier if you just look at it the way it's being displayed on screen (opened n PS).

[Katie Houghton]

You could set the pixel aspect ratio to square. View>Pixel Aspect Ratio>Square

• then transform the layer and make it skinner. CMD T or CTR T
• or Change the width only of the image. OPT CMD I or ALT CTR I (I used 91 % to match the .91 PAR)
• Finally you can always use the filter liquify. SHIFT CMD X or SHIFT CTR X for use of Face Detection.

[alisonl0shi]

I guess that's what I'll do -- I'll scale it down manually. Thank you Dave and Katie. Somehow in muddling through this all I have a better understanding of it all.

[davescm]

You're welcome

Dave