Why oh why oh why ... and what to do about it.

[jerry12953]

I've resized some images (650 pixels) using CS2 and converted them to jpegs to add to my website. File sizes are all about 40 - 60kb so they download nice and quickly.

When I come to sharpen them, it tells me that the file sizes are now about 800 kb and I have to resave them as jpegs which will surely mean losing quality.

Is it something to do with the "document size" which has increased to 22.93 cm?

Any suggestions before I start tearing my hair out?

 

[jpwone]

The document size should make no difference to the file size unless you are changing either the document size and retaining the dpi or changing the dpi and keeping the document size the same. In this case you saved at 72 dpi which converts to approx. 23 cm (650/72 = 9 inches = 23 cm).

The dpi (hence document size) is usually only used for hard copy print. For web display the size in pixels is used.

It is usual to get a small increase in size when sharpening but not of the order you are getting. There has to be something else happening.

I would suggest going back to the original and resize and sharpen and then save. This is a better work flow than resize save sharpen save again.

 

[Chappers]

JPEG compression tries to keep the file as small as possible, within it's parameter and constraints. It's possible that the sharpening is making it expand the file size. Look a a selection of files all initially the same size and saved with the same compression. You'll notice a difference, as the the subject matter affects what the jpeg compression can do.

However an increase from 60Kb to 800 Kb does seem a bit odd. Check the document size that may be the answer

 

[jerry12953]

The document size should make no difference to the file size unless you are changing either the document size and retaining the dpi or changing the dpi and keeping the document size the same. In this case you saved at 72 dpi which converts to approx. 23 cm (650/72 = 9 inches = 23 cm).

The dpi (hence document size) is usually only used for hard copy print. For web display the size in pixels is used.

It is usual to get a small increase in size when sharpening but not of the order you are getting. There has to be something else happening.

I would suggest going back to the original and resize and sharpen and then save. This is a better work flow than resize save sharpen save again.

I see where the document size is coming from - 650 divided by 72.

All the jpegs are sitting nicely in a folder, and I do a mouse-over on them and they come out at 650x433 (ish) with file size varying between 40 and 60 kb. That much I understand.

So I click on one and open it up in Photoshop; file size changes to 824.6 kb!

Perhaps interestingly the new larger file size doesn't vary according to the file size of the jpeg, only the dimensions of the image.

I do a quick smart sharpen; file size stays the same, I try to close it and the "jpeg options" box comes up

I've been led to believe that its best to re-sharpen after saving for the web, though, and I'm sure I've done it before.

Any more ideas while I still have a head of hair?

 

[CT]

I've been led to believe that its best to re-sharpen after saving for the web, though, and I'm sure I've done it before.

Any more ideas while I still have a head of hair?

That's contrary to what I always do Jerry - I always sharpen after downsizing and before saving. I don't do 'Save For Web' though, I resize the image specifying the dimensions I want it, then use the compression slider to get a physical file size suitable for wherever I'm uploading it to.

 

[MisterE]

Personally I would never have considered sharpening after reducing the file size, and have never done so. All my sharpening has been done before any resizing. I would look closely at pictures done both ways and see if you can actually see any difference. But then few people, if any, will be looking so closely anyway.

 

[CT]

Personally I would never have considered sharpening after reducing the file size, and have never done so. All my sharpening has been done before any resizing. I would look closely at pictures done both ways and see if you can actually see any difference. But then few people, if any, will be looking so closely anyway.

You have seriously got to be kidding! Take any pic you like and reduce it to forum size and you will see an obvious reduction in sharpness. The same thing applies if you rotate an image even a degree or two. It leaps out off the screen and I'm sure it's responsible for more soft images we see posted here than anything else. :shrug:

 

[Tyke Tiler]

You have seriously got to be kidding! Take any pic you like and reduce it to forum size and you will see an obvious reduction in sharpness. The same thing applies if you rotate an image even a degree or two. It leaps out off the screen and I'm sure it's responsible for more soft images we see posted here than anything else. :shrug:

CT is 100% Correct.

 

[jerry12953]

That's contrary to what I always do Jerry - I always sharpen after downsizing and before saving. I don't do 'Save For Web' though, I resize the image specifying the dimensions I want it, then use the compression slider to get a physical file size suitable for wherever I'm uploading it to.

I've followed the workflow you suggest here CT, and it works. I get my 40kb image ready to upload, because its been sharpened already. Great!

Interestingly, though, if I then open it up in PS, the file size immediately leaps to 824.6kb. Strange, or what?

"Save for the Web" seems to work OK as well.

 

[CT]

I dunno Jerry tbh, but I like to upload my pics to hosting sites resized to 800 pixels on the longest side and sharpened at that size. With a lot of these web sites if you leave it to their software to resize the image you just don't know how they'll look, so I prefer to take the matter out of their hands.

Strange behaviour there with PS, which I have but rarely use, so I dunno.

 

[jpwone]

Jerry are you talking about the size displayed at the bottom of the editing window in the status bar? I thought you meant the size after saving but if it is the size displayed in the editing window then this is normal.

See http://graphicssoft.about.com/od/photoshop/ig/The-Photoshop-CS2-Workspace/document2.htm

The file size displayed in Photoshop is the non-compressed base image size not the size the image will be when saved or even the size of image that was opened. The file sizes in the 'save' dialogue box take into account any compression and show the approx. size after saving.

HTH

John

 

[jerry12953]

Jerry are you talking about the size displayed at the bottom of the editing window in the status bar? I thought you meant the size after saving but if it is the size displayed in the editing window then this is normal.

See http://graphicssoft.about.com/od/photoshop/ig/The-Photoshop-CS2-Workspace/document2.htm

The file size displayed in Photoshop is the non-compressed base image size not the size the image will be when saved or even the size of image that was opened. The file sizes in the 'save' dialogue box take into account any compression and show the approx. size after saving.

HTH

John

Thanks, John. it looks like you may have come up with the answer, so I'll have a look at it again when I've got a bit more time.