G-CIVP
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Resizing Question

Sun Mar 26, 2017 11:38 pm

I hope someone can shed some light on this. When I resize in PS, I get 1024 by 687 pixels rather than 1024 by 683. Can anyone tell me why the 4 pixel difference? It is becoming annoying! Thanks in advance.
 
vikkyvik
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Re: Resizing Question

Mon Mar 27, 2017 12:47 am

G-CIVP wrote:
When I resize in PS, I get 1024 by 687 pixels rather than 1024 by 683. Can anyone tell me why the 4 pixel difference? It is becoming annoying!


What's the full (un-resized) resolution of your photos?
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DM
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Re: Resizing Question

Mon Mar 27, 2017 9:29 am

If you have the crop tool set to 3:2 and you're getting 1024 x 687 after resizing you should try resizing in steps. For example when I resize a 3:2 crop and the photo's width exceeds 3000px but not 4000px I'll resize 3000 x 2000 -> 2000 x 1333 -> 1000 x 667. I noticed that when I was resizing a 16:9 crop straight down to 1000 x 563 from a 3000px+ width it would resize to 1000 x 562 but after resizing in steps it always resizes to 1000 x 563. If you use a width of 1024px I would resize like 3072 x 2048 -> 2048 x 1365 -> 1024 x 683 or if you have photo widths greater than 4100px but less than 5000px for example then 4096 x 2731 -> 3072 x 2048 -> 2048 x 1365 -> 1024 x 683. Also I think resizing in steps may give you a slightly better looking photo than resizing all in one go but it's very minor like 1 or 2%.
 
G-CIVP
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Re: Resizing Question

Mon Mar 27, 2017 10:11 am

DM - It shouldn't be that complex! I think I probably need to reset my crop size. I'm actually working in cm as ultimately, I want to edit my photos for prints and have a smart key set up to measure the width left between the edge of the image and front nose/tailend after cropping to avoid bits being chopped off.

Vikkyvik - Will need to check but straight out the can.
 
vikkyvik
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Re: Resizing Question

Mon Mar 27, 2017 2:38 pm

G-CIVP wrote:
Vikkyvik - Will need to check but straight out the can.


What camera?
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G-CIVP
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Re: Resizing Question

Mon Mar 27, 2017 8:58 pm

Canon 60D. Switching to working mm rather than cm has seemingly resolved the issue. My next question is adjusting the dpi.
 
vikkyvik
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Re: Resizing Question

Tue Mar 28, 2017 4:38 am

G-CIVP wrote:
Switching to working mm rather than cm has seemingly resolved the issue.


Weird, not sure why that makes a difference.

Why not just work in pixels?

G-CIVP wrote:
My next question is adjusting the dpi.


Doesn't matter for digital files. Unless you're making prints.
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G-CIVP
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Re: Resizing Question

Tue Mar 28, 2017 4:48 pm

Vikkyvik - I was using cm for cropping but to two decimel places which I suspect was causing the slight anomaly. When I changed the rulers to mm, the issue resolved itself. As for DPI, I'm interested to know whether there is a quick way to reduce to 1024 x 683 and reduce the DPI at the same time for internet images.
 
vikkyvik
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Re: Resizing Question

Wed Mar 29, 2017 5:24 pm

G-CIVP wrote:
As for DPI, I'm interested to know whether there is a quick way to reduce to 1024 x 683 and reduce the DPI at the same time for internet images.


As noted, DPI doesn't matter for digital display of images. A 1024x683 image is a 1024x683 image, whether it's displayed on a high-res monitor or low-res monitor, or high pixel-per-inch monitor or low pixel-per-inch monitor.
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G-CIVP
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Re: Resizing Question

Wed Mar 29, 2017 11:12 pm

But the DPI does vary. Anet photographers who display their images on Flickr manage to reduce their DPI to 72dpi whereas mine come out at 500 dpi plus.
 
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Kaphias
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Re: Resizing Question

Thu Mar 30, 2017 12:26 am

G-CIVP wrote:
But the DPI does vary. Anet photographers who display their images on Flickr manage to reduce their DPI to 72dpi whereas mine come out at 500 dpi plus.

...which doesn't matter at all, since the images are displayed on Flickr, rather than being printed.

Dpi only needs to be considered when you are printing an image. It has absolutely no effect on images displayed digitally.
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vikkyvik
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Re: Resizing Question

Thu Mar 30, 2017 1:48 am

G-CIVP wrote:
But the DPI does vary. Anet photographers who display their images on Flickr manage to reduce their DPI to 72dpi whereas mine come out at 500 dpi plus.


72 dpi is pretty typical for computer monitors (or it used to be, not sure if it still is), though it's more accurately stated as 72 ppi (pixels per inch).

No matter what the image dpi is set to, you're going to see it on your screen at your screen's ppi.

Again, dpi doesn't matter for digitally viewed images.
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dvincent
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Re: Resizing Question

Thu Mar 30, 2017 1:44 pm

Some cameras have a slight vertical resolution difference, and this can be affected by RAW converters as well (they might expose a few more vertical lines).

The 60D is specified as 5184x3456, which should downsample to 1024x673. However, that may not be the actual source res you're sampling from. Mathematically, it should end up at 683 vertical lines, so I would look at other things. Are the photos cropped at all, and what program are you using to crop? If you're using LR, for example, you might want to specifically choose 3:2 as the crop ratio, versus "original" and then try re-exporting again.

There are also some sensors that are slightly taller despite being 3:2, but the 60D's is not one of them.
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scbriml
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Re: Resizing Question

Fri Mar 31, 2017 6:07 pm

G-CIVP wrote:
I hope someone can shed some light on this. When I resize in PS, I get 1024 by 687 pixels rather than 1024 by 683. Can anyone tell me why the 4 pixel difference? It is becoming annoying! Thanks in advance.


Are you cropping to 3:2 ratio before resizing?

I always crop to 3:2 before resizing and always get the correct number of pixels. However, my straight-out-of-the-camera (Nikon) RAW size is very slightly less than true 3:2, if I resize without cropping, I get an 'incorrect' vertical size.

G-CIVP wrote:
DM - It shouldn't be that complex!


It certainly shouldn't be. I have to admit I've never understood why some people insist images need to be resized in stages.
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dvincent
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Re: Resizing Question

Sun Apr 02, 2017 3:51 am

In the bad old days downsampling algorithms weren't that good, so people downsampled in stages to avoid blurriness.

Nowadays they're a ton better and resampling in stages is not necessary.
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