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Welcome to Michael's blog. Michael Andrew, (aka Michael The Maven) is a freelance producer, photography instructor, tech innovator, and when needed, disaster aid specialist. Disclaimer: Michael is a participant in Bhphoto & Amazon affiliate programs that provides an advertising commission if you purchase through links on this website.


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04.16.12         photography  

Why Canon 5Diii Owners Should Save JPEGs if Shooting with ISOs over 500


If you own a 5Diii you can do these tests at home, just make absolutely sure that your subject matter is identical between shots.

The short answer on this is:

If you own a 5Diii and are shooting at ISOs between 640-3200, you should seriously consider at least using Standard ISO noise reduction and saving a JPEG copy.

The longer answer:

I have done many, many tests now on the 5Diii and have learned some very interesting things, and most of it has to do with the file size of the image in higher ISOs with the 5D iii. For the most part, whenever photographers compare ISO noise ranges, it is a visual comparison of images themselves. Subject matter has a huge role in how "clean" an image looks, so I decided to take a different look at what happens to the file size with higher ISOs.

In most cameras, file sizes increase with increasing ISO. For example, if you were to put your 5Diii on a tripod and take an image in AV mode, of a completely still subject 10 times, the file size will stay pretty much the same.

Assuming your ISO noise reduction is turned off, as you increase your ISO, the file size will also increase, because ISO noise must be considered as part of the interpolation of the image. A single noisy pixel has to be calculated which increases the file size, the more noise, the larger the file. I have a great video on Youtube explaining how a pixel gets its color here: How a Pixel Gets Its Color

The idea of the ISO noise reduction, is a processing feature of JPEGs which is meant to reduce visual grain. We can also safely assume, that the less noise there is in one image, the smaller the file size, all other things being equal.

WIth the 7D and 5Dii, the file sizes generally increase with an increase in ISO. More so with the 7D than the 5Dii, as the 5Dii seems to maintain about the same between 640-1200.

BUT… and this is the kicker: The file size of the Canon 5Diii actually gets SMALLER from an ISO of 500-640, its typically 5-20% between those two settings, depending on subject matter. This is significant. In fact when I plotted it out on a graph that first night, it looks like this:
This was something I noticed the first day I got the camera, and you can see my initial results and images here: Michael's Canon 5Diii High ISO Tests

I thought this was an error on my part at first, but it turns out to be completely reproducible.

After more testing, I have also learned:

- This does not happen when you are shooting RAW
- This does not happen when you are shooting video (there is some very slight changes between 500-640, but nothing huge). Video is a completely different ball game.
- This does not happen when you have ISO noise reduction turned off. Nearly all of my tests were done with Standard ISO noise reduction.

I do not pretend to know how this file size shrinking is happening, but I do know that the most common way for a JPEG image of equal resolution to decrease in file size is compression. My gut feeling is that the phenomena we are seeing here is not traditional compression, but rather an algorithm specific to the 5Diii.

There is a way to test to see if it is classical compression, but its a little involved, if I get a chance I will try to do it. Again remember, we do not see these file size changes in RAW images. If you must shoot RAW, yes, you can clean up the image using various software, but how well it cleans up depends on 1- The software itself, 2- the skill & knowledge of the person operating it, and it is 3- going to take some time, and yes the results will vary from person to person.

Canon knows it's sensors better than anyone and I believe what we are seeing is some type of new ISO noise clean up strategy that is being done in camera by the 5Diii. My personal take is that the 5Diii ISO noise starts to fall apart around 3200, but I know many other sources who think its closer to 6400.

So again, the take home message is this: If you own a 5Diii and are shooting in the range of 640-3200, take advantage of this ISO noise reduction feature and save a copy in JPEG. In most cases, as far as ISO noise, it is going to look better and work faster than cleaning it up in post production. This is especially true if you are a wedding photographer, and you are shooting a couple thousand images in these ranges, say... at a reception, this is a good piece of information to have. Your images should look cleaner, and without the high ISO clean up hassle.

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