JPEG File Sizes - What's Going On?


petebfrance 6 2.7k France
12 Oct 2017 12:01PM
I've been doing some processing on various raw (DNG) files, and notice the huge difference between JPEGs produced from tifs compared to the original in-camera version. Interesting, but I wonder if the large size is really necessary / contains more information etc. The resulting image does look better to me, but.....

Example from 16mp (12 bit) photo:
DNG 11.9mb
JPEG from camera 6.07mb
JPEG from tif 21.4mb (at 100 'quality')
The tif was about 44mb, but I deleted that....
all done in Faststone, btw.

I know I could (and probably will) go ferreting around the internet and find an answer but thought it maybe would make an interesting discussion....





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Tianshi_angie 3 2.1k England
12 Oct 2017 12:14PM
Jpegs have been a hobby horse of mine for some time and although folk say they have improved they still throw a tremendous amount of information away which cannot be restored. As I understand it most of the information that they do discard is colour information which I think is critical to an image looking its best, even if it will be processed into a B&W. When I first had a digital camera I did my processing with PhotoImpact (long since absorbed into Corel's Photo? ) but when you saved an image the size of the original and the resulting Jpeg were shown alongside thumbnails of each image. It wasn't until I had ruined several hundreds of images that I realised what a difference it made. But Jpegs are better now - I still don't use them except for email and the net!
petebfrance 6 2.7k France
12 Oct 2017 12:37PM
Tianshi_angie thanks. So do you keep the tifs or is there another format that you use? I'm already running out of space on my hard drive - could of course 'archive' things, or convert as needed etc., but even the processed JPEGs (as opposed to in-camera ones) take up an awful lot of space.
ChrisV Plus
11 2.3k 26 United Kingdom
12 Oct 2017 2:23PM
Don't know about 'Fastone' peter, but have you checked the bit depth of your post-TIFF jpeg? The most likely culprit for the size increase is if it's saving as a 16bit [as opposed to 8bit] file.

JPEG is now probably on its way out - the more modern alternatives just needed a major player to champion them. Apple has just switched to HEIF.
Dave_Canon 12 1.4k United Kingdom
12 Oct 2017 3:15PM
The most important issue is that some formats like Raw, TIFF, PSD are lossless but other format notably JPEG use lossy compression. For example if you save an image in TIFF, when you next open that image you will get exactly the same image pixel for pixel. However, JPEG uses a compression format which reduces the size by approximating. So large areas of a similar colour may be recorded as a single colour. Rather than recoding each pixel, the information is stored as say 12 pixels @ colour X which takes up much less space than recording the colours individually. The net result is that when you open a JPEG file, you are only seeing an approximation of your original image file. If you set a High Quality setting the image is recorded more accurately but at the expense of a large file. Conversely if you choose Low Quality, you can have a small file size.

In many situations, if you choose a medium to High quality and do not edit then you will notice little difference for most requirements. However, there is a particular problem if you edit and re-edit. Each time you edit, save, re-open a JPEG file you obtain an approximation of an approximation and the quality deteriorates with visible artefacts appearing in the image. Many, use Raw and during the editing process save as a TIFF or PSD until all editing is complete which avoids these effects. You can then save a final version in JPEG. I personally only capture Raw and Save my final edited versions as TIFF files; I also save the original Raw file. I sometimes produce JPEG versions for competitions, ePhotozine etc. but these are temporary which I then delete. I can always produce later JPEGs from the TIFF files and the JPEG requirements vary anyway.

Dave
petebfrance 6 2.7k France
12 Oct 2017 3:28PM
No idea, Chris, can't really tell but it is saved as 'uncompressed.'
The options it gives are UNCOMPRESSED, LZW, JPEG (when saving as tif - seems odd), PACKBITS G3FAX1D, G3FAX2D, G4FAX.
Actually, it's an old version so I must update it, but I thought the whole idea of converting to tifs was so that there was a file with all the information to work from. I gather than if adjustments are made against the raw (dng) in Faststone they are being applied purely to the JPEG stored in the raw file and not to the raw file itself.
I think I'm confused (to put it mildly!)
petebfrance 6 2.7k France
12 Oct 2017 3:35PM
Thanks Dave_Canon. Yes, that's the reason why I'm using the original raws. I'm assuming that the in-camera JPEGs have a higher level of compression than the ones from the tif (is it capital letters?) at 100 quality and that's why they are smaller - but that suggests that in-camera JPEGs (at least from my camera) are less than optimal to start out with.
Interesting stuff, really......
petebfrance 6 2.7k France
12 Oct 2017 4:13PM
Back to Chris' question, it looks like the tif was 8 bit. I loaded up Silkypix (which came with the camera) and saved an 8 bit tiff which gave me a 46mb file and a 16 bit tif which gave 92mb. I think I've already broken Silkypix, by the way - not fatally, but I deleted a file it produced while the program was still open and it now gives bizarre filenames when I convert.
Philh04 Plus
13 1.9k United Kingdom
12 Oct 2017 5:03PM
JPEG files are only of any use for posting onto the internet or for sending a proof image to a client etc, yes they have the advantage of smaller file size which maximises your storage but should really only be considered if you are not going to do any further editing etc., it does take a large number of saves for any degradation to become evident and they also have the disadvantage of only being able to work in 8bits.

The size of a JPEG file will vary according to the level of compression and the amount of detail, a high ISO file will often be larger due to the amount of 'noise'

Workflows are currently heading towards the non-destructive raw route, i.e. adjustments are made to the file in an application like Lightroom and files, either JPEG or TIFF (yes it does have caps as it is an acronym Smile ) are output as and when needed for purpose, for example sending to an outside printer etc.

At the end of the day it comes down to you being happy with the way you work... I would prefer to save out as a TIFF file (Layers can be saved too) and spend a little on external HD's for storage.

Hope that makes sense... (just realised, I don't think I answered your question or did I, busy day)
Chris_L Plus
4 4.8k United Kingdom
12 Oct 2017 5:03PM
The in camera jpegs probably compress at much less than a quality of 100. They are possibly at 70 or 80 quality. You can shave a lot off file sizes when you start lowering the quality without noticing too much visual difference depending on the type of scene and the colours.

The Photoshop preset for High Quality JPEG is set at a mere 60, Medium Quality JPEG is 30
petebfrance 6 2.7k France
12 Oct 2017 5:22PM
Interesting, thanks Chris (L this time) an Philh. So I'm left wondering if people save uncompressed or compressed TIFFs, but happy with the JPEG conundrum!

Thanks all!
Tianshi_angie 3 2.1k England
12 Oct 2017 5:26PM
I do have several external hard drives which I use to save all my Tiffs and Raws. Different drives for different cameras with current images on the computers own drive but copied to an external drive - so that is 4 external drives all attached to the computer and a further external drive which is used to do a complete back up of all working files but not attached except when the back-up is done. Don't back up programmes as I reckon they can be re-downloaded if the worst happens - and it has in the past.
12 Oct 2017 6:07PM
I scan film negatives as DNG and then after processing save as a TIFF with a JPEG as a small file for quick viewing - it's not hard to get a gigabyte medium format scan. On digital, I always shoot both raw and JPEG, the raw file is the "negative" as it were, and the JPEG is the pound-store 6x4 print.

JPEG is more than good enough for viewing on a computer screen, but as others have noted it is a "lossy" compression system & in these days of multi-terabyte drives for a hundred quid or so it's probably not much good as a primary storage format. I fondly recall my old S602Zoom camera which came with a 16Mb card - on maximum resolution, you could fit just one image on the card. That was in the days when tens of images were being upload to the Interweb every hour.
banehawi Plus
14 1.9k 3926 Canada
12 Oct 2017 6:54PM
I think one of the answers is that most people, - cant speak for everyone, wont save enormous TIFF files. You can save the original DNG which is efficient for space, and produce a jpeg form the DNG when you need to
saltireblue Plus
8 8.4k 33 Norway
12 Oct 2017 7:28PM

Quote:Many, use Raw and during the editing process save as a TIFF or PSD until all editing is complete which avoids these effects. You can then save a final version in JPEG. I personally only capture Raw and Save my final edited versions as TIFF files; I also save the original Raw file. I sometimes produce JPEG versions for competitions, ePhotozine etc. but these are temporary which I then delete. I can always produce later JPEGs from the TIFF files and the JPEG requirements vary anyway.

That's my preferred workflow, too.


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