What ho one and all,

I normally shoot for stock and my MO is shoot RAW, open with ACR, fiddle around and save as the largest pixel offering in 16 bit tif. Then I have plenty of leeway for PS editing.

However, I have been doing a bit of pro bono work for my local parish council; pretty much reportage of local events, so lots of images have been created. If I go my normal processing route, it will take forever and at the end of the day, they only want jpg, not tif files.

In the past, I have found that using my normal MO, I can get an A4, 8 bit tif, save it as a jpg, and it is around (for example, 10mb.) Given that I know the pixel measurements, if I open the RAW reportage images in ACR, correct and set the defaults to the same pixel measurement, then hit the Save button, the saved file, although more or less A4 overall, is around half the mb size (or less) than a similar saved from an 8 bit tif.

So my question is, what is the difference between converting from an A4 tif and saving as a jpg, or saving straight from ACR. Both files are overall, A4, but the mb count is significantly different. What data is being lost? What difference does that 'lost' data make to image quality?

Toodle pip and thanks

Rex