JPG files changing size on me

mitchell65 said:

Just done a test. I just added a tag to an image that was 6.22Mb. Just the one tag and the file size is down to 5.83Mb. Can only assume that as soon as you hit "Save" further slight compression of the image takes place as it always does when using JPEG's. Also the degree of compression would be the same as the degree used in the first instance. My editor has a range from 1 to 12 so if you chose 9 in the first place this would be the standard for all subsequent "saves". Have just done the same exercise with a PNG image. No change in file size here. Much as I would expect as PNG is not a lossy format. No compression takes place when you save it. So I would conclude that what you are getting is normal for a JPEG! On normal monitors this would make no noticeable difference to the quality, only if you were doing high quality printing to the image maximum size would it notice and then you would probably use a non lossy format anyway.
Answer is, if quality really matters, if you can't shoot the original in a RAW format, use the highest quality JPEG you camera will go to and then save the image to PNG or TIF before anything else and stay in that format until the last minute before you save for the final time, even after adding your titles, tags etc, then save to the highest quality JPEG your editor will go to.

Thanks for the responses.

These were all scanned family pictures from slides or pictures. So while quality was always important it wasn't critical. I had read about the issue with the JPEG losing quality with every edit. So I always did test edits and saves, and you are right, on the monitor I could never notice a difference even at low % saves, but I always saved closed to the original size on the edits. Of course when I reduced a file with a long side of 2500 down to 1600 the file size would change quite a bit.

The editors I mentioned before all used a % for the compression save option. I would do test saves to determine what would give me a comparable size file. It was 85% with Corel and 90% with the Nikon (or vice versa). The Photoscape batch was saved at 95%.

All pictures went through 2 "edits". The first was for quality (dust, color etc.). the second was for size. So about 9,000 pictures went through a save of 85% or 90% on the quality edit and then another 85% or 90% on the size edit. The final 1,000 went through 85% or 90% and then the 95% size edit. Yet the first batch is saving at a large decrease on my title edit, while the second batch is saving at an increase on my title edit.

Doesn't make much sense, but as mentioned I can notice no difference in the quality on the monitor. Just a bit concerned about the arbitrary drop on the one batch when all I'm doing is adding data.

fimble said:

if you renamed the same file half a dozen times and it was compressing to 75% of its original, your final image would be under 20% the size (quality) of the original (first) jpeg image.

It's a good theory. I just did a test of that, and I "re-titled" a file 5 times. The only change in size was on the initial change.

And to be clear, I'm making a distinction between "renaming" and "retitling". I renamed the files a number of times (keep them in numerical order). And have changed or added "titles" this one additional since the initial scans this one time. As you may notice from my later post, some of them are increasing in size with the change.

mitchell65 said:

Try a tes like this:
If one batch you edited and saved to JPEG and chose a low number in the quality then that would give you a reduction in file size. If in the other batch you chose the maximum number, probably 10 or even 12 the there would be practically no extra compression but a filter added or similar would increase the file size. The only real way to check this is to take one image as a "control". Edit it by adding a filter and using an unsharp mask then save it to the max quality number the editor allows. Then take the original control image and do the same editing, using the same editor but save it to say 6 or 7 quality. Then compare!

Will do the suggested tests now. It's too late to fix what I've already done since I'm done scanning and quality editing, but I am curious as heck.

Early in the thread I thought you said you weren't doing any subsequent editing/compression and just adding meta data?

Okie Dokie. I did the test and got the results I would have expected. Virtually no change in the file size with just adding a title as a final step regardless what I did in the prior editing process.

I took an unedited original scan. I then ran 4 copies of the same pic through the Corel editor with a "1 step photo fix" edit. I then saved two of them at the maximum setting and two at the reduced one I was using (I was wrong, Corel doesn't use a %, it's a sliding scale from 1-maximum to 99-minimum. I'm sure the Nikon View editor used a %, and the PhotoScape definitely does.) The settings I used for the test were 1 and 9.

I then took those four results, and reduced the size of the pics, two in Corel and two in PhotoScape. The original size was 2592 X 1680 and both programs reduced it down to 1500 X 972. I then took the 8 pics (original size and reduced size), and added titles to them in Windows Explorer. There was nothing but small changes after that change, and subsequent re-naming produced no change.

Here are the results:

Corel/Corel ............4,521...4,503.....576...578
Corel/Corel ............1,164...1,165.....585...586
Corel/PhotoScape....4,521...4,503...1,181...1,188
Corel/PhotoScape....1,164...1,165.....525...532

The first number is the size after the first photo edit.
The second number is the size after adding the title on only the photo edit.
The third number is the size after the photo and reduction edit.
The last number is the size after adding the title after the photo and reduction edit.

The original file size was 874.

So, it does me no good, it appears that something happened along the way to mess up the bulk of the files. I think I did most of the original size reductions with Nikon NX, so maybe something in that process. A good deal of my editing was done with the Nikon too, but I had earlier done some of the title additions with no adverse effect (that I noticed), so I'm at a loss.

The numbers may look a little confusing, but the one (and only) interesting ones are that when reducing the picture size on Corel, the initial larger pic ended up being smaller than the initial smaller pic after the reduction. 4521 to 576 and 1165 to 585. Makes no sense, but I think I'm giving up. Thanks for the input.

mjf said:

Early in the thread I thought you said you weren't doing any subsequent editing/compression and just adding meta data?

That's correct. Just trying to re-create what has gone wrong. All I have done is added titles and the size is dropping.

mitchell65 said:

Hi Nailgunner
Well we may never know what happened initially. It may become one of "Lifes big mysteries". On a lighter note and with tongue in cheek, I calculated that if you made a continuous slideshow of all of your images and gave each imade a 5 second slot, the slideshow would last for twelve and a half hours. Makes me quite glad that I am not one of you lucky relatives! (Just joking)

No, there is no joking about it. You should be glad. there are actually 11,333 total to be exact, but who's counting.

My initial plan was to get them all on a 2gb flash drive, which was why I had to reduce them. Then I decided to put them all up on SkyDrive with the "original" and "edited" version so if someone didn't like my editing job they could download the original and have at it. Then my mom found another 1666 slides (that number has not escaped my amused attention) and my 2gb plan flew out the window. Which was okay since I hadn't bought the drives yet and then stumbled on a 4gb drive sale for $10 at Office Depot about 2 months ago, but I wouldn't have had to change the picture size.

So if anyone is curious, SkyDrive doesn't have a limit on the number of files you can store on there since I have about 23,000 up there now. They do limit you to a 200 file at a time upload though.

But to REALLY confuse my issue, I overlooked and didn't realize a "slight" part of the equation when I outlined this. As I said above, I have each picture as an original and an edited. After an edit I would just save the new one with the same number in a different folder. 99% of the pictures I was making changes to the description were on original pictures. And the only edit I technically made to them was when I downsized them. Some of them dropped the description altogether so I must not have had the "save exif" box checked on some of them (which doesn't make a lot of sense). It just didn't dawn on me until late last night that the files I was having the issue with were not the full edited ones. And yes, when I've changed a description on an edited picture (none of those were lost, just spelling errors), they increase in size a bit after the change. So my test yesterday was a waste of time.

So my new conclusion is I'm really confused now. I did all of the batch size reductions at basically the same time. And I wasn't in the habit of checking and un-checking the "save exif" box. I did change scanners in the process of all this, and it is a basically a certain batch of files that the description was dropped on. But only on the originals and not the edited. And I would enter in the description on the original scan, and match up the edited file description later. Something must have corrupted a narrow range of the files somehow, or something. So this will remain unsolved.

Anyway, I apologize for the length of the posts and the ensuing confusion. I still can't believe I didn't make the connection that it was un-edited files. Thanks again for the input. And like I told my relatives when I sent them the email about how to get on SkyDrive, they were still going to get the edited pictures so they could have them all on their computers and share in my misery, and I have now passed on some of that misery to you all. (It's not ALL that bad for them, I have it broken down by person/subject. So if a sibling only wants to see their goofy looking kid and not another siblings goofy looking kid, I made it easy for them )