Compressing photos to less than 30K

IN PS use Image size to reduce the size of the image in pixels - ensure that the ratio is maintained

Typical web size is less than 600 pixels on the horizontal axis.

Then is save as select a middle to low quality - remember to save to a different file name to avoid overwriting your original image file

Or get hold of a copy of PMView if you are on 'doze it has an easy to use size process.

I've just tried doing it with Windows photo editor, reducing a pic from 4 meg down to 29k at 115x85, but it's flippin' awful!

Tony

Cheers for that Derek

I resize in XP My Pictures first then compress using this:

xat.com JPEG Optimizer

It was a time-limited download but the compression still works after expiry.

In the next few posts, I'll upload two photos (of exactly the same pixel dimensions -- 500x335) to illustrate what JPEG compression looks like. As you'll see, the amount of compression possible before artifact uglies rear their head depends on the amount of detail in the image and, of course, how much the image is compressed.

Here are some examples of JPEG compression of a low-detail 500x335 pixel image.

Bay at dusk -- 40k (looks OK to me)

Bay at dusk -- 25k (almost as good)

Bay at dusk -- 15k (starting to lose smoothness in sky and water)

Bay at dusk -- 10k (uggh)

Bay at dusk -- 7k (Blah! the smallest size I could make this file)

Here are some examples of JPEG compression of a moderately high detail 500x335 pixel image.

D&J -- 40k (barely acceptable)

(same pixel dimensions and file size as the bay picture, but the added detail in the couple shot required more JPEG compression to reach the target 40k file size)

D&J -- 25k (yuk!)

D&J -- 15k (truly crap; the smallest size I could make this file)

Tried last night and not had much success with this. The results were appallingly pixellated

Basically the originals were 6 Mb RAW files I had manipulated and converted to 12 compression (ie least) approx 2Mb 8 bit JPegs

The only way I could get them to below 30K was to use full (0) Jpeg compression and drop the pixel dimension to about 170 width (in landscape)

Comparatively, your lowest resolution ones Joe are superb!! How did you go so low? Are my original Raw/Jpeg files just too large?

Bosh,
I'm no expert but I think the answer is as follows:

1) Taking low resolution pics in the first place is likely to be detrimental, if anything.

2) Converting to jpeg should be the last stage of the process.

3) A degree of processing that might seem appropriate for the original pic - especially sharpening - can harm the quality of any reduced-pixel pic made from the processed pic. So, I would recommend re-sizing (pixels) before most types of processing. [Some processing is probably best done first but the results tend not to be significantly worse when done after resizing].

With the free program that I use, Photoimpact 5, sharpening is the last thing I do before converting to jpeg, and I sharpen only as much as is absolutely necessary. Incidentally, Photoimpact 5 has a "Compress by Size" option, which does its best to compress to the size you specify.

Perhaps someone else could confirm/correct this, as appropriate?

Bosh,

quote:

Comparatively, your lowest resolution ones Joe are superb!! How did you go so low? Are my original Raw/Jpeg files just too large?

I opened a RAW file (actually, a Nikon NEF, their version of RAW) in Photoshop CS, did a few quick colour and tone adjustments, resized the image to 500 x 335 pixels (a reasonable size for Web use or for e-mailing to friends), applied unsharp masking, then did "Save for Web" under the File menu.

When you do "Save for Web," a box comes up that lets you choose file type (JPEG, GIF, PNG, etc.) and its quality. With JPEGs, you can choose between 100 (best quality) and 0 (worst quality). I just slid the slider back and forth until I got a JPEG of the desired file sizes -- 40kb, 25kb, 15kb, etc.

If you look at the two examples, the bay picture suffers much less from JPEG compression than the couple shot, so this is very much subject dependent. In other words, high-detail images suffer much more from JPEG compression than low-detail ones.

Joe

P.S. All the pix I uploaded are the same resolution (500x335). What varies is the amount of JPEG compression applied to those images. You can, of course, make files smaller by reducing their resolution.

The JPEG optimiser in Paint Shop Pro does a great job, shows before and after & is very easy to use. Just resize the photo first then go file-export-jpeg optimiser.

Jobs a good'un. Thanks Joe

No one using "semantic compression" first mooted, I think by Nicholas Negroponte of MIT's Media Lab, or "fractal compression" used by microsofts 'Encarta' ?

/dl