Compressing Jpegs to a specific size

[Fistorey]

Images need to be resized from LARGE Tiffs or Jpegs to a specific web size BUT still keeping the image quality...
Image Size: 1600px long side, 72DPI and each shot compressed and sharpened for web with no file over 130kb.
File size needs to be 130kb or under - then when opened in photoshop - image "expands" to 4MB+
There are hundreds of images so i need to BATCH.

I can't seem to get the images under 130kb without losing quality and without changing the file size... Jpeg opens in Photoshop as is (i.e.. compression is unsuccessful... opens at 130kb and not 4Mb+)

Hope this makes sense!

I need urgent help.
Thanks.

 

[MrToM]

Can you remove the text formatting from your post please?

(Or can a mod do it for them?)

Those of us using the 'Dark' theme cannot read your post...



Thank-you.

Regards.
MrToM.

 

[gedstar]

MrToM

Should be OK now

 

[MrToM]

Top man!

Thanks gedstar

Regards.
MrToM.

 

[MrToM]

Brace yourself for some bad news.

...Images need to be resized from LARGE Tiffs or Jpegs to a specific web size BUT still keeping the image quality...

Not really possible.

The action of re-sampling inherently changes the so called 'quality', its unavoidable.

...File size needs to be 130kb or under - then when opened in photoshop - image "expands" to 4MB+

Not sure what you mean here by 'expands'.

...I can't seem to get the images under 130kb without losing quality...

Sorry but you never will so I'd stop trying.

...Jpeg opens in Photoshop as is (i.e.. compression is unsuccessful... opens at 130kb and not 4Mb+)

This line probably makes the most sense and leads me to think you are interpreting 'compression' in totally the wrong way.

Jpeg isn't an image file format, its a method of image compression but not the kind of compression as in a .zip or .rar file but as in a permanent reduction in the size of a file by removing data from the image.

Without getting too technical about it the image has information removed from the individual pixel data, and pixels themselves if you re-sample the image, (as you've indicated you want to do). this is a PERMANENT operation, irreversible.

reading between the lines, so I may be way off base here, it appears that you want to reduce the filesize in order to display on a web page?

There are systems that can be implemented in the source code of your web page that will take a large image file, create a NEW image file of smaller dimensions for display on the page and create a link to the fullsize image should it needed to be viewed at fullsize.

Photoshop is most definitely not the software you need to be looking at, you are asking the impossible.

Look toward using web software (such as ImageMagick) to handle your display criteria for web images....it's what it was designed to do.

Sorry if that's not what you wanted to hear but honestly, using Photoshop is not the solution to your problem.

Regards.
MrToM.

 

[Fistorey]

H MrToM,

Thank you for your advise.
Apologies as I may have the incorrect terminology... I am still at a bit of a loss though.
I do understand that one can resize images for web to 130kb and click to view larger. I have been asked by a client to supply images as a certain spec - and they sent me the the following image as an example.
See attached.

1. When I view the image size it reads as 130kb.
2. Then when I open it in photoshop and view image size it is 4Mb+

This image sits in an image gallery on the clients website. Thumbnail gallery > click to view larger.

If this cannot be done in Photoshop and I will not be using the web software(you suggested ImageMagick), as the client handles their own website... any other suggestions for software?
I currently process the image from RAW in Capture One Pro.

Thanks again for all your help.

 

[MrToM]

Ah....you didn't mention you use a mac, sorry, I'm a PC guy.

It shouldn't make any difference but It would probably be best for another mac user to guide you through the process.

From what you've [now] said it [now] does seem to be an easier task than I first read, sorry for any confusion on my part.

One thing I can tell you is that you can ignore the filesize PS gives you in that dialog. This refers to the filesize of the PSD file should you save it for later editing, it is not a representation of the output filesize.
(Because PS cannot possibly know how you intend to save the output file.)

Regards.
MrToM.

 

[Jerry D]

1. When I view the image size it reads as 130kb.
2. Then when I open it in photoshop and view image size it is 4Mb+

I think the confusion here is the "pixel dimensions" is not the image size on disk but the number of pixels in the image itself.

 

[thebestcpu]

Hi Fistorey

Two separate topics.

1) If you have an adobe subscription you have Lightroom as well and its export function allows JPEG compression to a specific file size and can be done in batch mode. Photoshop can also do this in Save for Web yet don't think the fixed image size can be batched. I don't see the ability in Capture One Pro to create a specific file size either.

So if you have LR, I recommend using that for batch mode to create JPEGs in a specific files size


2) As far as a 130kb file becoming 4MB. That is just the difference between the external compresed format in JPEG at a certain compression setting vs the internal file size in Photoshop.

Here is what determines the internal file size for an 8 bit RGB image

Internal File Size (in MB) = Pixel Wide x Pixel Height x 3 / 1024 / 1024

Note: For an 8 bit depth file the file size requires 1 byte for each color channel or 3 bytes for RGB (which is why you multiply by 3)

Note: if you have a 16 bit depth file instead of 8 bit depth you mutlitply by 6 instead of 8. Also, the division by the first 1024 turns bytes into kilobytes ( KB) and the second division by 1024 turns it into Megabytes (MB) (1024 is used because of easy binary arithmetic 1024 = 2^10 = 2x2x2x2x2x2x2x2x2x2). Go figure

So in your exmaple Inter files size MB = 1600 x 1065 x 3 /1024 / 1024 = 4.875183 MB = 4.88 MB when rounded

Hope this helps a bit

John Wheeler

 

[Fistorey]

SUCCESS!

I think I may have figured it out.
In Capture One Pro >
Process images as a Tiff at 1600px at 72dpi … THEN… SAVE AGAIN (in Photoshop) as a medium size Jpeg. = 130kb file on disc
BUT… when opened in Photoshop its a 4MB+ file

Yay!!!