jpg vs. bmp

[Mr-H]

Just out of interest, been doing a lot of scanning of photos lately, and nor sure whether to save them as .jpg or .bmp. It appears as though .bmp files are a lot larger and therefore take up more space. Is this true? Which is the better of the two? You IT experts out there - which one would you choose?

[dr b]

jpg compresses the file (that's why it's smaller) and therefore throws away some information, but that's undetectable for most pictures. bmp (or tiff) does not compress and so saves everything; that's why it's larger. For most applications it does not matter, therefore jpg is "better" because it saves on storage.

If you're going to do a lot of editing of the pictures, or print out big blowups, bmp might be best, but if you're just going to look at them onscreen, jpg is fine.

[Buenchico]

Raw bitmaps (.bmp) are uncompressed files and thus contain every bit of available data.. Jpegs (.jpg)are compressed, so that some data is lost. (The actual level of compression, and thus the subsequent data loss, can - with any decent program - be determined by the user. You might have to go into the 'advanced' settings of your scanner program to find where to change the level of compression).

For the vast majority of uses, jpegs are perfectly good enough. That's why most mobile phones and cheap digital cameras will only save image files as jpegs (and why more expensive cameras will always use 'jpeg' as the default image type - which only a tiny percentage of users ever even consider changing it).

Try a few test scans, saving the results as both jpegs and raw bitmaps. View the results on your screen. Then print the images. I'll be amazed if you can see any difference, either on screen or on paper. Unless you can, you might as well save everything directly into .jpg format.

Chris

[Mr-H]

Thanks guys (both of you). I did notice that a lot of the single pictures are almost 2mb each, and some pages from the original file (containing up to 6 photos) can be 10+ mb. Next question, if I'm going to keep them on the PC (as I suspect) how do I change them from .bmp to .jpg? Individually, or can it be done as a group?

[Buenchico]

How you change them will depend upon which software you use. Irfanview is an excellent (free) image viewing program, which deserves a place on every PC. But it's also useful for basic image manipulation requirements (such as removing 'red-eye' or changing brightness and contrast) and great for file conversions (either individually or in bulk), such as the ones you're considering:
http://www.irfanview.com/

First, create an empty folder (anywhere you like), to hold your converted image files.
In Irfanview, go to File > Batch Conversion/Rename
Check that 'Batch conversion' is selected under 'Work as'
Use the navigation facilities, at the top right, to go to the folder which holds the bmp files you want to change to jpegs. (Thumbnails will be displayed in the pane)
Assuming that you want to convert every file in that folder, click 'Add all'. (Otherwise click on individual files and then click 'Add'. To select a block of files, click on the first one then hold down 'Shift' while clicking on the last one. To select a group of individual files, click on them (one by one) while holding down Ctrl).
Check that the output format is set to JPG
Use the 'Browse' button to navigate to the folder where you want the converted files to go.
Click 'Start batch'

Chris

[Mr-H]

Just done this with one folder containing 143 images. File size overall reduced from 271mb to 9.8mb.What a reduction/increase in available space!! Brilliant - many thanks!

[fo3nix]

But note that in doing that, you may have lost a lot of information that was in the original photos.

I'd personally save your photos as tiffs if possible.

jpegs are, as above, compressed, but they use lossy compression. This means that every time you open them, make a small change (take out red-eye or something), you lose quality.

The same isn't true with tiff or bmp, but tiffs are better than bmps are they can store different types of metadata.