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iPhoneArt Studio Talk - Exif data loss!!!
 

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Exif data loss!!!

Img_1959

Jahsharn
Member since 05.12.11

Good morning from the UK, this question was posted a year ago by a member called TALSH, I was wondering if anyone had an update on it?
OUESTION:
I'm somewhat new to iPhoneography, and was wondering if there is a preferred way to retain any and all EXIf data even after editing a photo in various apps. Currently, after running a photo through several processing apps all EXIF data is gone. I have noticed, however, that saving a processed and EXIF-less image from the Camera+ light box will add 'iPhone 4' as the camera used. Geo-location, however, is still stripped. Any thoughts or tips on this issue? Do you mind the loss of EXIf data?

Thanks

Paula x

posted about 2 years
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kaphinga
Member since 23.01.11

Thanks @wildaker! I might have to look into the GoPro option on Photogene.

I now see that Photoforge will let you specify the quality and file type. ... If you save to the Documents directory.

posted about 2 years ago
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wildaker
Member since 20.11.12

@kaphinga: might be worth digging a little deeper in the settings of some apps. I don't know all the apps intimately, but PhotoForge2 *does* allow you to save with minimal JPEG compression (or PNG or even—I've now discovered—TIFF) to *some* of the places it can save files. Camera Roll? No. But DropBox? Yes!

Also, Photogene² has the Go-PRO in-app purchase that, among other things, allows for JOEG quality to be set. It's $7.99, but it *is* there as an option...

posted about 2 years ago
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kaphinga
Member since 23.01.11

Huge thanks to @wildaker for taking the time to explain the details of how Jpg compression works!

For whatever it is worth, I just did a little experiment to try to figure out the jpeg quality that apps produce. I took a picture with 645Pro set at high quality, and then I opened and saved the file in some of the big editing apps. My original image from 645 Pro was about 8MB. Most of the apps --- Snapseed, iPhoto, photogene, and photoforge2 --- saved the image at about 2MB. The only exception was Filterstorm, which was able to save the file at 8MB.

The bottom line --- from now on, when I shoot with 645Pro, I am going to edit with Filterstorm.

posted about 2 years ago
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wildaker
Member since 20.11.12

If you're shooting RAW with a Nikon, the odds are that you're using very mature, well-behaved editing software developed by businesses with many years of dealing with the needs of professional and serious amateur photographers; software that preserves EXIF data through the editing process.

The iOS imaging world is less mature, and not all developers of all apps are aware of the importance of doing so—something that I expect to evolve very rapidly, however. After all, the entire industry is only really five years old!

posted about 2 years ago
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Jahsharn
Member since 05.12.11

Wow!! Thank you @Wildaker and everyone else who has contributed to this studio talk. You all have given me a very indepth lesson in exif data and way more. I suppose I'm so use to using my Nikon and shooting in Raw format seeing all metadata available for reference. It was frustrating me that using an IOS device would be so different in that respect. Thank you all once again, Paula x

posted about 2 years ago
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wildaker
Member since 20.11.12

To answer the opening question, there is no way to prevent apps that process your images from modifying (which includes removing) the EXIF data (something I'm using here as a loose, but convenient shorthand for all the metadata—EXIF and other—as many photographers do).

However, there's another issue that is highlighted by Mike's posting. If you open an image in an iOS app (or, indeed, any image editing app on your computer), change something, and then re-save it as a JPEG, the image will be compressed, which means if it was already a JPEG it will be recompressed*.

Each stage of JPEG compression will, due to the nature of that compression, tend to introduce "compression artefacts" and compound those that are already there from any previous compression stages. Furthermore, very few iOS image editing apps—including some very, very good ones—offer any control over the level of JPEG compression that has been applied.

What this means in practice is that, even if you start with a very high quality JPEG such as those delivered by 645 PRO or (more recently) Pro Camera at their maximum JPEG setting, opening it and editing it in another app leads to a high likelihood of the image being saved, automatically, at a much higher level of compression (which means a lower technical quality). Note that this even applies with an app that appears not to modify the pixels in any way, but simply the EXIF data.

If you really care about image quality at a technical level, it's important to seek out those editing tools that allow you to control the JPEG compression level when you save your edit. For maximum image fidelity, shoot in TIFF—there are now several apps that allow for this—and edit with tools that allow you to save images that have no (or, the same thing in practice) non-lossy compression applied. On iOS, that means PNG, as I don't believe any iOS apps yet support a pure TIFF workflow; on the desktop it generally means sticking with TIFF or PSD through the editing process. Only save as JPEG, with minimal compression, for final distribution.

And, just to confirm, the image *dimensions* are the number of pixels it has, the *resolution* is the density of those pixels when they are rendered (on paper or on a display), and *technical quality* (or image integrity) should be used to refer to the closeness or otherwise of the image data to the actual pixels captured by the image sensor.

A final point: many people are extremely happy with the technical quality of images that have been compressed and recompressed multiple times at standard JPEG levels of compression and they're not wrong to be so (how can they be?). However, there are others who care deeply about the changes these processes involve—maybe because they are looking to print their final output at large sizes, where artefacts are far more visible, or simply because they care about the *principle* of the thing!

(Full disclosure: I'm the Founder of Jag.gr, which developed 645 PRO, among other apps.)

* There are a very few simple actions—specifically, rotation—where well-behaved apps won't need to recompress a JPEG, so the recompression is not 100% inevitable, before anyone jumps on me—only 99.9% or so...

posted about 2 years ago
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kaphinga
Member since 23.01.11

I wouldn't sweat it too much, Mike. A lower compression ratio can still look really good in print. Whether the compression is noticeable really depends on the the image. In general, hard edged things will show more artifacts than softer edged things. I suspect that NoImgData is saving at a compression rate similar to most other apps. The difference is that 645Pro can save at *extremely* high quality, which makes for a very big file. If I understand it correctly, there is a huge difference in file size between the highest quality compression and the second highest quality compression.

posted about 2 years ago
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frankensinatra
Member since 08.11.11

Could it be slightly possible yall are wrong? Even a little bit? I've been using it for months and all my photos are fine, print fine, look sharp.

http://lifeinlofi.com/2012/06/29/noimgdata-free-promo-codes-0612/

posted about 2 years ago
Img_6427

kaphinga
Member since 23.01.11

Momentsforzen is right. noImgData is not changing the pixel dimensions, but I will bet it is changing the JPG compression level. It would be especially noticeable on images coming from 645Pro, which can save very high quality jpegs.

posted about 2 years ago
1387707451

frankensinatra
Member since 08.11.11

It does not change resolution. I know better then that ;)

posted about 2 years ago
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Tenorsoul
Member since 12.02.12

I verified the changes after noIMGdata: the size changed of around 200 Ko. It didn't modified the resolution

posted about 2 years ago
Img_1959

Jahsharn
Member since 05.12.11

Thanks Mike & Marie, it is a bit frustrating but I'm going to look at the apps mentioned before. As stated it would so cool if the developers did look into this more. Oh well, hope you all have a wonderful day xx

posted about 2 years ago
Img_6427

kaphinga
Member since 23.01.11

Hey Mike, if you are going from 5mb to 1.5mb, you are losing a lot more than exif data. Exif data is really tiny.

posted about 2 years ago
1387707451

frankensinatra
Member since 08.11.11

I usually remove exif data from my photos with noIMGdata to save memory. For instance taking a photo with 645 pro, mine was 5.40775 MB, after I removed exif data it was 1.53162 MB. That's a big difference! I don't see stuff like that as important. But it seems like you could replace it back on a basic pc with windows, right? Other then that I don't know of a iphone app that can do it. I do know camera+ adds it's own to any photo you process through it.

posted about 2 years ago
Img_1959

Jahsharn
Member since 05.12.11

Thank you all so much, when my wifi is working properly I'm going to try out the ones mentioned. You're all so wonderful in helping and old gal out xxx hope you're having a wonderful weekend.

posted about 2 years ago