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Forum Discussion
does Dropbox compressed photo files???
I'm sending full resolution photo files to clients instead of burning them on a disc, but I want to make sure they are the full resolution. I had a client that had pictures made at Walgreens, and they were pixely..I told her not to resize them at all o her end, but now I'm wondering if they are compressed at all and no longer full resolution. If so, I need to go back to discs.
Thanks!
I uploaded a 107.5MB TIFF file to Dropbox using a desktop browser, then downloaded the file. I then compared the file in my download folder to the source file.
Both were exact matches down to the byte: 107,525,5436 bytes.
I then checked for JPG. Also an exact match 9,177,764 bytes.
Then I checked CR2 files (Cannon's proprietary file extension)
Drumroll...both files were 23,921,835 bytes.
If you are using some mobile app to upload your photos...switch to desktop if you care about such things, but blame the right party.
Last I checked, I do not work for Dropbox, nor do I own any stock. If you call someone a liar, you better be able to back it up at least as well as dropbox backs up your files.
The idea of compressing or encrypting the files is useful. The downside is it does break workflow and certainly can't be used with something automated like Dropbox's photo uploader.
I just saw this post, and I can confirm to all that dropbox DOES NOT MODIFY photos.
The dropbox app on pc/mac doesnt even know what a photo is!
It syncs FILES it doesnt change your word document fonts, it doesnt change the format of the cells on your spreadsheet, it doesnt remove records from your database file, and it doesnt reimage your .jpg files (or any others)
The dropbox app simply sees files and uploads and syncs them.
It doesnt care what type of file it is,
FYI: dropbox does now additionally add a ads metadata to all files in the dropbox folder, but this is an alternative data stream and does not relate to the original data stream of the file.
That is 100% not the case with the mobile photo uploader, which I have spent some time studying.
https://blog.night-shade.org.uk/2015/06/why-does-dropbox-add-a-unique-id-to-every-photo/
https://blog.night-shade.org.uk/2015/06/dropbox-iphone-camera-upload-changes-photos/
There are files available on github if you want to study them yourself.
https://github.com/TimJDFletcher/IMG_7082
Tim : I just went to your test data, and i didnt find it very helpful,
the AFC.JPG is Image Size : 3264x2448
the dropbox.jpg is Image Size : 2448x3264
So between one and two its been rotated?
I also just uploaded some pics via my phone then compared them to the orginals and they are not different. I even did one on its side where the picture shows upright. Same result same file,
Mine is the android app tho so maybe a difference?
The work flow I have as testing was:
- Take image and on phone
- Transfer image to computer / cloud service using different methods
- Check image for changes using md5 or sha1 checksums
Photos can be the same resolution but a different quality, note the reduction in size in the Dropbox image from 2.8MB to 1.79MB with a loss of quality.
My issue is one of honesty as I explained in the post about this. I understand and accept that cloud services need to compress files but they also need to be clear about this.
@Tim thank you for your tests. I'm wondering, should we take this up on Reddit? Maybe we can get more traction there since Dropbox, inc doesn't want to chime in.
Maybe we "the people" will have more info on there.
- Ed
Dropbox Staff
Hi Tim
I just double checked with one of our engineers and we don't compress photos at all. There might be something else changing the resolution during the upload time. If you want, please write us on www.dropbox.com/support with detailed description of your original file and how you see it on Dropbox, including the methods you're using to upload them, so our team can investigate it further.
Please do not disclose any personal information on the forum.
Thanks!
Hi Ed,
Thanks for looking at this, could you check with your engineering team about the Camera Upload feature please. This is the feature that I have done detailed testing on and which is changing the file size and hash as well as adding the unique ID.
If your engineer could look at the write up that I did and explain the changes that would be great.
Hi.
I've just compare photos i've uploaded with Camera Upload and same photos I've pulled out from iPhone with iExplorer. For comparing I used dupeGuru with content binary compare.
About 300 of 560 photos was changed.
P.S.: no advertising here.
Over the last few days, I've noticed a significant degradation of some images that I've uploaded to DB. Is it possible that there's a new compression algorithm at work? I understand that previously DB has stated that there's no compression at work. Maybe that's true, maybe it's not. I've always noticed some minor loss of clarity. But what I've seen over the last few days crosses be boundary of what's acceptable and what is not. Thoughts anyone?
