Image Size Question

[Goody13]

I am puzzled and am wondering whether someone can help to "unpuzzle" me. I have been scanning some old prints to send to someone to publish in a book they are compiling. When I scan them, they are typically around the 700Kb size. As they are over 20 years old, I am taking the opportunity to sharpen them up and do some lighting correction where needed using DPP, which I find is particulalrly good for sharpening.

I am then batch processing, but cannot understand why, when the new image is saved, it is larger than the original image by some 20%.

Within DPP, I have the image quality for conversion set to 8, which I presume is OK, it is being saved as an Exif-JPEG with an output resolution of 300dpi, which is the same resolution I am scanning at.

Does this sound correct? I am e-mailing the photos for publication so want to do them at a decent quality.

I am just curious, as it does not seem logical to me that if I am not saving at the maximum quality of 10 when converting, that the converted file size is larger than the original. :shrug:

 

[TheBigYin]

if you've created any additional detail (or enhanced any noise!) by sharpening the file, it'll make the file larger. To illustrate this, create a file in your editor the same size as your image file. Make this empty file all white, and save it at the same image quality setting you're using. Then compare the file sizes. The all white block will be much, much smaller than a normal picture. The more often the colour changes from one pixel to the other, the less compression you'll get.

Also, are you embedding a preview image in the edited/saved file... this will obviously make the saved file bigger.

 

[Goody13]

Thanks. That seems to make sense; changes made to the picture increase file size. I am sharpening most of them. I suppose that it would be even bigger if I used a quality size of 10 instead of 8.

As to embedding a preview image, I do not know how to do that or how it works, so am unsure. I am fairly new to editing and learning the benfits as I go along. I cannot believe how my old pictures are so much better after firstly using the colour correction on the scanner and then sharpening in DPP, although I also cannot help but feel it is cheating a bit!

 

[TheBigYin]

If you were working with print's from back in the day, they may have been printed "sub optimal", and may indeed have faded with time. I've been ploughing my way through a couple of tea chests full of photo's going back to shots of my grandad in his Uniform before going off to WWI. The worst of the shots have been the 70's colour photos which had been processed by cheap mail order processing companies.

Amazingly, whilst the photo's were absoloute dreck, the negatives were in pretty good order, and after pushing them through my scanner, I've recovered some lovely looking shots of my parents. Hard to believe that the prints were so awful in comparison.

Very, very few colour prints were processed and printed on properly colour corrected machines back in the day. All you're doing in applying a tweak or two, and sharpening them up is what you'd have been able to do in a proper wet darkroom, had you had the kit and training to do so. All the computer is doing, is making it more accessible to everyone.