Skip to main content
R
rivalg
Known Participant
June 9, 2020
Question

Resizing functionality in PS (2020)

  • June 9, 2020
  • 3 replies
  • 1230 views

I’ve two questions regarding resizing images in PS. 


I need to recover a number of pictures that I deleted in LightRoom; I have the thumbnails of these, created when I imported them into LR. 

If I resize these in PS, what image quality would I get? 

Some sources inform me, a thumbnail does not have enough information, and resizing it will not bring back the original image quality. I that is the case, how much quality could I recover by resizing them.

 

I resized in PS several images already; I noticed when I uploaded in PS, the image resize function revealed the image was 3.4MB in size. Apple’s Finder info revealed it was only 72Kb. 

 

In PS, I only changed the resolution to 300 ppi; automatically, the width and height were changed. At that point, the dialog informed me the size of the image was now 64MB. I saved the image. Finder informed the resized image was 3.4MB. 

I wonder why is the reported size so different in PS and Apple. 


I appreciate any comments you might have on these questions. 

FYI: Adobe CC subscriber; PS, LR CC, and MAC OS all updated to their latest versions. 

 

This topic has been closed for replies.

3 replies

R
rivalgAuthor
Known Participant
June 14, 2020

Conrad,

 

My belated thanks for your reply. 

 

Your answer helped me understand the diference. 

 

r.

Conrad_C
Community Expert
Conrad_CCommunity Expert
Community Expert
June 9, 2020

rivalg wrote:

I wonder why is the reported size so different in PS and Apple. 

 

Photoshop reports the true uncompressed file size of an image; in other words, the data size that results from doing the math on, for example, bits per pixel * the number of pixels * the number of channels. That is usually a much larger number than what you see on the desktop, because…

 

The Mac Finder (or Windows Explorer) desktop reports the size of the file resulting from both the file format and the amount of compression. This is the reason we don’t compare “quality” using file size: The same 300 x 200 pixel image could have several very different file sizes on the desktop depending on which file format they were saved in (JPEG? PSD? TIFF?), the bits per channel of the file (8? 16? 32?), whether high or low compression was used, etc. So file size is an extremely unreliable way to compare image quality. Much better to compare using pixel dimensions (e.g., 300 x 200 px vs 3000 x 2000 px).

 

If you want more details about that, you can read the following article (disclaimer: I wrote it):

Know Your Photoshop File Sizes

    D Fosse
    Community Expert
    D FosseCommunity Expert
    Community Expert
    June 9, 2020

    This is all about pixels. Watch the pixels. Forget ppi or file size on disk.

     

    An image is measured in how many pixels. Increasing pixel size will bloat file size, but do nothing for quality. On the contrary, the result will usually look a whole lot worse. Don't do it, don't even think about it.

     

    The jpeg file format uses very aggressive data compression to reduce storage size on disk. It's just packaging on disk. When the file is reopened, the data are decompressed and the file size returns. Hence the apparent difference (which isn't real).

     

    Lots of people misunderstand ppi. It's not a native property of the file. It's an instruction about pixel density in print, determining how big the available pixels will print on paper. It's still just pixels. To help understand, read it absolutely literally, word for word: pixels per inch. It means exactly what it says, no more, no less.

    R
    rivalgAuthor
    Known Participant
    June 9, 2020

    Thank you for your reply.

     

    I am still one of those people who misunderstands ppi.

     

    Maybe I should have asked: when using the resizing function in PS to enlarge an image, what does the user accomplish? Does the user gets just a bloated image? 

    Conrad_C
    Community Expert
    Conrad_CCommunity Expert
    Community Expert
    June 9, 2020

    Bojan, 

     

    You helped me in my understanding of what PS does with its image size function. 

     

    I have several LightRoom standard preview thumbnails about the 300x200 px size - Would it be a cause of further frustration to me in trying upscale these by, say,  between 150 - 250%. How do I know what percentage is best? My eyesight is not a good judge for that.

     

    I do not necessarily wish to have all of these, but a few, printed;  I am more interested all my photos display in a screen computer as the originals would.

     

    Thank you.


    rivalg — When you use the Image > Image Size command to try and upscale the 300 x 200 px images, you probably want to set the Resample Image option to Preserve Details 2.0 because it is significantly better than the other methods for upscaling.

     

     

    But even then, realistically it may be difficult to maintain quality at more than 200% enlargement. So don’t be surprised if it’s hard to preserve quality when you try to enlarge beyond 600 to 800 px on the long side. That only gives you a good quality print at a few inches long. A big part of the problem is that 300 x 200 px is just not that much to start with. It would have been much easier to upscale to a print-quality image if there were more than 1000 pixels on a side.

     

    The percentage you should try depends on the quality of what you have to start with, so it’s hard to recommend a specific number. You are probably going to have to run a few tests and see how far you can push it.

    Terms & ConditionsAccessibility statement
    Using the community Terms of use Privacy Cookie preferences Do not sell or share my personal information ad choicesAdChoices