does Dropbox compressed photo files???

@Bryan R.: Your not getting a comment because they have commented over and over and said the same thing over and over, NO DB DOES NOT CHANGE YOUR FILES.

Now what I would suggest to you is this:

Stop comparing your ORIGINAL files to the online PREVIEWS of them.

Next time download the file you uploaded and compare the two, since they will be exactly the same file I doubt you will find any difference.

Hi Dave,

Have you read the extensive post I wrote, including full details of how to test and reproduce the change to photos using the iOS Dropbox app?

Could you follow the process that I outlined in my post, ie upload via iOS Dropbox "Camera Upload" feature and then compare the files copied from the phone using a different method such as iCloud photo sync.

@Tim F. : see previous reply on test data (this thread)

@Tim F: I read your blog post. To be clear, you are talking about the Dropbox iOS app's Camera Upload feature, correct?

"I have used the Dropbox Camera Upload feature for about 18 months to get photos off my iPhone..."

But then here you wrote:

"First of all I extracted a single photo IMG_7082 directly from my iPhone via USB. I copied the file out of the DCIM folder on the phone, which gave me a 2.8MB file as my “master copy”. Checking my Dropbox folder I found the file with the same name had a different checksum and is over 1 megabyte smaller, the plot thickens!"

If you had used the app's Camera Upload feature, the photo would not be named IMG_7082. Are you sure that's how you got that file into your Dropbox account?

@Kevin you are correct I found the file from the date and timestamp not the file name, I've corrected the post

The file was transferred via Dropbox camera upload, as you can see from the Github repo I tested multiple file transfer methods, and labelled each one.

@Dave nowhere in this thread has anyone actually tested the Camera Upload feature, there are others testing via a normal upload via desktop or web client not via Camera Upload.

@Tim F.

You need to make clear VERY CLEAR what your talking about.

You keep naming the iOS Phone app as the "Camera Upload feature", but the "Camera Upload feature" is part of the "Desktop app" (see preferences/import/camera upload), this I have used and it uploads the files the same.

As I run Android I dont have the iOS app installed, however I contacted someone with a iphone and they assure me the photos went up from it the same as well, he has 20+ years of computer technical experience and would not be making a mistake.

I suspect something else on the phone may be involved. (unproven)

dave232

Dropbox call the feature Camera Upload here: https://help.dropbox.com/syncing-uploads/upload-mobile

So you are telling me that you have not tested this yourself, please rather than poking at other people take the time to test.

I would also suggest asking your computer expect friend to checksum photos uploaded via Dropbox and via other means. Someone with that level of expertise would take only 5 minutes to make these checks.

@Tim F.

Sorry but i think you're being a bit slow as I said, I have an Android phone so CAN'T test it myself, telling me I should go and test it is simply ignoring what I have said or failing to read it.

And anyway, I did have it tested as I said, and he didn't "checksum" the files he didn't need to he performed a binary compare on the data and found it identical. 

The orginal files consisted of 4 camera photos, 4 existing photos, 4 added photos

The original files were compared to (1) web downloads from DB : identical

The original files were compared to (2) desktop synced from DB : identical (data stream)

The only differences detected was the addition of the DB ADS stream attached to the file when downloaded via the desktop client, for most users they would not even know this exists, and its content has no reference to the datastream.

@ Dave

I think you should test it yourself and not just repeat what you have heard from other people.

I also have an Android phone and I'm using the Dropbox automatic upload feature on my phone to sync my pictures with Dropbox.

And I do see a difference in file size when comparing pictures pulled directly of my phone with those that have been stored in Dropbox. The file sizes of the Dropbox pictures are consistently smaller than those pulled directly of my phone. The difference isn't very large but it is definitely there.

To give you an example:

File downloaded from phone -> 5.18 MB (5.438.227 bytes)

Same file downloaded from Dropbox -> 5.04 MB (5.295.779 bytes)

So about 2.5% smaller. And this is about the reduction i see with all my other pictures too.

The resolution of the pictures hasn't changed though and even upon close inspection I can't discern any difference in image quality.

But the fact remains that picture files do get changed when they are automatically uploaded to Dropbox from an Android phone.

And I for one would like to know why and what happens to them exactly.