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Photoshop Image Size & Resolution

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Myer

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I hope somebody can explain this to me.

I use Photoshop CS6 and ACR to process my RAW images.

When I have an image that's in the range of 5184 x 3456 with a resolution of 288 in Photoshop it does not appear to be very sharp.

Then when I change it to 1024 x 683 with a resolution of 72 it appears very sharp (no PP other than resizing as above).

I asked a friend what he thought. In doing so I emailed him both images and copied them back to me.

When I opened them in my email both images appeared to have the same amount of sharpness.

Why would one in Photoshop appear to be much sharper and not so when opened in my email?
 
Myer said:
I hope somebody can explain this to me.

I use Photoshop CS6 and ACR to process my RAW images.

When I have an image that's in the range of 5184 x 3456 with a resolution of 288 in Photoshop it does not appear to be very sharp.

Then when I change it to 1024 x 683 with a resolution of 72 it appears very sharp (no PP other than resizing as above).

I asked a friend what he thought. In doing so I emailed him both images and copied them back to me.

When I opened them in my email both images appeared to have the same amount of sharpness.

Why would one in Photoshop appear to be much sharper and not so when opened in my email?
Click to expand...
This has nothing to do with the resolution, but with the magnification factor when the image is displayed. I think it also depends on your graphics card, but at magnifications like 50% and 25% the image should look sharp, while at for example 33% it will look a bit fuzzy. That is because you look at a resampled image.

--
Johan
http://www.johanfoto.com
 
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Myer said:
I hope somebody can explain this to me.

I use Photoshop CS6 and ACR to process my RAW images.

When I have an image that's in the range of 5184 x 3456 with a resolution of 288 in Photoshop it does not appear to be very sharp.
Click to expand...
Presumably, this is the size of the raw as it came from the camera?
Myer said:
Then when I change it to 1024 x 683 with a resolution of 72 it appears very sharp (no PP other than resizing as above).
Click to expand...
Is this smaller image also opened in Photoshop?

If you were enlarging the smaller one, I'd say it was pixelation but that won't be the case as you reduce its size.

I'll have to think on this!
Myer said:
I asked a friend what he thought. In doing so I emailed him both images and copied them back to me.

When I opened them in my email both images appeared to have the same amount of sharpness.

Why would one in Photoshop appear to be much sharper and not so when opened in my email?
Click to expand...
The resolution that you type in (288 or 72) makes no difference to an image displayed on your monitor.


"It's good to be . . . . . . . . . Me!"
 
What you need to get a handle on is Interpolation(Resampling) every time you interpolate an image and commit the result you wind up with an entirely new image not a single pixel from the prior image exist and some image quality has been lost. For you ether throw away details you had or create details you don't have.

How much quality you lose depends the change in number of pixels, the interpolation method used and the quality of the pixels you had to start with.

You should not interpolate more than once.

If you feel you may need several size changes create a smart object first. Every time you resize a smart object you start with the original pixels you had for the Smart object pixels do not change.

You can resize a smart object many times using transform. It is like a single interpolation for you always start with the smart object pixels which are not changed in the resize process. The resize has lower image quality then the smart object however you still have the smart object. You still have what you started with. When you resize an actual raster layer with a transform or all raster layers using menu Image>Image Size you no longer have what you had you lost some image quality and you will continue to loose more image quality with each additional resize

-
JJMack
 
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JJMacks said:
What you need to get a handle on is Interpolation(Resampling) every time you interpolate an image and commit the result you wind up with an entirely new image not a single pixel from the prior image exist and some image quality has been lost. For you ether throw away details you had or create derails you don't have.

How much quality you lose depends the change in number of pixels, the interpolation method used and the quality of the pixels you had to start with.

You should not interpolate more than once.

If you feel you may need several size changes create a smart object first. Every time to resize a smart object you start with the original pixels you had for the Smart object pixels do not change.

You can resize a smart object many times using transform. It is like a single interpolation for you always start with the smart object pixels which are not changed in the resize process. The resize has lower image quality then the smart object however you still have the smart object. You still have what to started with. When you resize an actual raster layer with a transform or all raster layers using menu Image>Image Size you no longer have what you had you lost some image quality and you will continue to loose more image quality with each additional resize

-
JJMack
Click to expand...
I understand how interpolation works but the issue here is not that re-sizing is causing the problem; it's quite the opposite.

The originally sized image is the duff one.

I've just had a thought.

Surely you can't re-size a raw in Photoshop (I assume you mean ACR)?

Therefore your sharper, smaller image must be something else, Jpeg. probably, in which case, at least some, processing will have taken place.


"It's good to be . . . . . . . . . Me!"
 
Johanfoto said:
This has nothing to do with the resolution, but with the magnification factor when the image is displayed.
Click to expand...
that's right -- open the original and downsized images in ps and hit ctrl+0 (fit to screen) for both - they will look the same
 
I'll reread all of the posts in the morning.

Thanks.

I take the RAW and do some processing and save it as a jpg.

Then I need a final image that has a resolution of 72 and a horizontal of no more than 1024 and a vertical of no more than 768.

I want to keep the larger image so I end up with two; the larger that is the one from ACR that has been cropped in PS and the smaller that has been shrunk.

I'll reread all the posts and try to figure them out.

Thanks so far.
 
Myer said:
Then I need a final image that has a resolution of 72
Click to expand...
why do you think you need a final image with res 72? i don't think you understand what resolution is

--
sara
 
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Myer said:
When I have an image that's in the range of 5184 x 3456 with a resolution of 288 in Photoshop it does not appear to be very sharp.

Then when I change it to 1024 x 683 with a resolution of 72 it appears very sharp (no PP other than resizing as above).
Click to expand...
There could be many things affecting this. When you reduce it to 1024 x 768, you are downsampling (merging original pixels into new pixels) and that can have an apparent sharpening effect. It's one reason some videographers like to shoot in 4K even though their final output is just 2K; the 4K footage downsampled to 2K looks cleaner and sharper than if it was shot at 2K to start with.

Also, if the resizing was done in Photoshop, then the Resample interpolation set in Image Size will affect sharpness of the resized image. If it is set to Bicubic Sharper (which I think Auto will choose when downsampling), then the downsampled image will have more sharpening applied than for instance if you had chosen Bicubic.
 
I belong to a couple of camera clubs.

Photos submitted for our competitions must be as follows:

Resolution: 72

Maximum width: 1024 (could be less)

Maximum height: 768 (could be less)
 
Myer said:
I belong to a couple of camera clubs.

Photos submitted for our competitions must be as follows:

Resolution: 72

Maximum width: 1024 (could be less)

Maximum height: 768 (could be less)
Click to expand...
A digital image has no resolution. It only has a pixel size.

Yes, there is a resolution metadata field stored in the image, but it doesn’t do anything.
 
Mark S Abeln said:
A digital image has no resolution. It only has a pixel size.
Click to expand...
Digital image have both a number of pixels and a resolution setting. Display do not honor resolution the display images the resolution they are run at not the image set resolution. Display display image the wrong size ,Resolution is actually pixel size. Pixels have no size till a resolution is set. Pisels also have an aspect ratio. Photoshop handle different pixel aspect ration but can only display image using you displays square 1:1 aspect ratio pixels. Most Digital images have square aspect ratio pixels.

100DPI means pixels are 1/100"x1/100" there are 10,000 pixels per square inch.

300DPI means pixels are 1/300"x1/300" there are 90,000 pixels per square inch

So an image with 90,000 pixels would print 1"x1" at 300DPI and 3"x3" at 100DPI The same 90,000 pixel image prints 9 time bigger at 100dpi then at a 300dp resolutioni.

Resolution is pixel size pixel density not the number of pixels
 
I failed to include that the file size shouldn't be more than 1024 KB (1.024 MB).

The resolution affects the file size.
 
graybalanced said:
Myer said:
When I have an image that's in the range of 5184 x 3456 with a resolution of 288 in Photoshop it does not appear to be very sharp.

Then when I change it to 1024 x 683 with a resolution of 72 it appears very sharp (no PP other than resizing as above).
Click to expand...
There could be many things affecting this. When you reduce it to 1024 x 768, you are downsampling (merging original pixels into new pixels) and that can have an apparent sharpening effect. It's one reason some videographers like to shoot in 4K even though their final output is just 2K; the 4K footage downsampled to 2K looks cleaner and sharper than if it was shot at 2K to start with.

Also, if the resizing was done in Photoshop, then the Resample interpolation set in Image Size will affect sharpness of the resized image. If it is set to Bicubic Sharper (which I think Auto will choose when downsampling), then the downsampled image will have more sharpening applied than for instance if you had chosen Bicubic.
Click to expand...
easy to understand explanation. this is one of the reasons I suggest to friends and family not to delete images that aren't perfectly sharp. Often times they can be easily printed or resized for use online and that lack of sharpness will never be noticed. In fact they will look great.
 
graybalanced said:
Myer said:
When I have an image that's in the range of 5184 x 3456 with a resolution of 288 in Photoshop it does not appear to be very sharp.

Then when I change it to 1024 x 683 with a resolution of 72 it appears very sharp (no PP other than resizing as above).
Click to expand...
There could be many things affecting this. When you reduce it to 1024 x 768, you are downsampling (merging original pixels into new pixels) and that can have an apparent sharpening effect. It's one reason some videographers like to shoot in 4K even though their final output is just 2K; the 4K footage downsampled to 2K looks cleaner and sharper than if it was shot at 2K to start with.

Also, if the resizing was done in Photoshop, then the Resample interpolation set in Image Size will affect sharpness of the resized image. If it is set to Bicubic Sharper (which I think Auto will choose when downsampling), then the downsampled image will have more sharpening applied than for instance if you had chosen Bicubic.
Click to expand...
For downsampling, the lanczos algorithm is best. It looks sharp and clean yet very natural better then Photoshop's bicubic interpolation.
 
The Resolution setting in Photoshop is a common cause of questions here, and it is rather confusing.

Displays don’t honor the resolution setting, nor do consumer photo printers.

Digital files are abstract representations of images and have no intrinsic size in inches or centimeters, no matter what the resolution setting might be. Pixel count is all that matters, and pixels have no inherent size, since they are abstract numerical data and not anything physical. Changing the resolution (without resampling) does nothing whatsoever to the pixels: at best it is a hint; answering a question like “Does this image have enough pixels to be nicely printed at 16x20 inches?”

I frequently do work with publications that are printed on commercial web offset presses, and in this work, photos sizes indeed are specified according to inch dimensions and resolution settings (typically they want 300 pixels per inch); but these numbers are always taken together, which gives us — you guessed it — a pixel dimension. But specifying a resolution without also specifying an inch dimension is meaningless, for the image could be any size whatsoever.
 
Toermalijn said:
graybalanced said:
Also, if the resizing was done in Photoshop, then the Resample interpolation set in Image Size will affect sharpness of the resized image. If it is set to Bicubic Sharper (which I think Auto will choose when downsampling), then the downsampled image will have more sharpening applied than for instance if you had chosen Bicubic.
Click to expand...
For downsampling, the lanczos algorithm is best. It looks sharp and clean yet very natural better then Photoshop's bicubic interpolation.
Click to expand...
I use Lanczos myself; resampling images is something of an art, and care needs to be taken for quality work.

If your lens is soft, then just about any resampling algorithm will work OK, and some sort of sharpening afterwards may be needed to make the image look crisp. But if you have really sharp lenses, then resampling can be problematic, and the image may look really rough with some algorithms.
 
Myer said:
I failed to include that the file size shouldn't be more than 1024 KB (1.024 MB).
Click to expand...
What will strongly change the file size is the JPEG compression amount. The quality difference between Photoshop’s 12 and 9 compression is negligible, but the file size difference is quite large.
Myer said:
The resolution affects the file size.
Click to expand...
At the same final pixel dimensions?
 
Myer said:
I failed to include that the file size shouldn't be more than 1024 KB (1.024 MB).

The resolution affects the file size.
Click to expand...
if you keep the image dimensions at 1024 x 768, changing the resolution has no effect on file size
 
JJMacks said:
Mark Scott Abeln said:
A digital image has no resolution. It only has a pixel size.
Click to expand...
Digital image have both a number of pixels and a resolution setting. Display do not honor resolution the display images the resolution they are run at not the image set resolution. Display display image the wrong size ,Resolution is actually pixel size. Pixels have no size till a resolution is set. Pisels also have an aspect ratio. Photoshop handle different pixel aspect ration but can only display image using you displays square 1:1 aspect ratio pixels. Most Digital images have square aspect ratio pixels.

100DPI means pixels are 1/100"x1/100" there are 10,000 pixels per square inch.

300DPI means pixels are 1/300"x1/300" there are 90,000 pixels per square inch
Click to expand...
Nope.

Mark's right.

You need to read the contents of the link in my earlier post.

DPI and PPI, which is what you'e actually referring to here, are two completely different things.

PPI is a measurement of length, viz Pixels Per Inch along one side of the image.

DPI is a measurement used, erroneously, to represent the number of Dots Per (square) Inch, of ink that a printer will place upon the paper.

In reality, the printer works out the density of the dots it applies by using its own algrithms; the results of which will bear no resemblance to the figure that you type into the box in Photoshop, or whatever software you're using.
JJMacks said:
So an image with 90,000 pixels would print 1"x1" at 300DPI and 3"x3" at 100DPI The same 90,000 pixel image prints 9 time bigger at 100dpi then at a 300dp resolutioni.

Resolution is pixel size pixel density not the number of pixels
Click to expand...
Strictly speaking, it's neither.
JJMacks said:
JJMack
Click to expand...
"It's good to be . . . . . . . . . Me!"
 
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