The X-Factor of Fudging ISO

Started Jan 24, 2013 | Discussions thread
BillyInya Senior Member • Posts: 1,453
Re: My ISO precision test (3 cameras compared)

Bernie Ess wrote:

So this has been on my mind since I got my X-E1 2-3 weeks ago. Today in a lazyafternoon hour I set up a tripod and decided to compare 3 cameras I own (Fuji X-E1, Fuji S3pro and Canon 5dII) in terms of ISO precision.

I tried to rule out as many variables as possible, by using one and the same lens (a Nikon 105mm f2,5 Ai-S fully open @2,5) on all 3 cameras (on the Fuji and the Canon 5d II via Adapter, obviously, and at different ISOs.

I then shot all 3 cameras at 3 ISOs, 200, 400, 800. I started with ISO200, f2,5 at 1/125s, then ISO 400 at 1/250s, and ISO800 at 1/500s.

Then of course I compared the samples and ordered the 3 samples for 2 different ISO settings (ISO200 and 400) side to side in Photoshop and made a screen shot.

The part that is not 100% precise is that the files are somehow developped differently in camera or by the converter, they apply a brightness curve. But comparing in camera JPEG output and the RAW conversions offered by Lightroom, the order of how the 3 cameras came out stayed the same.All cameras were set to standard picture style with standard settings.

For the 5d II I had to move the tripod closer to the door, in order to get the same framing, more or less.

My montage of 2x3 = 6 photos is not particulary beautifully made, and the photo is plain boring, it shows the outside (sky) through my balcony door. But it allows to judge brightness easily.

In both rows, the X-E1 is left, S3pro in the middle and 5dII on the right.

As can be seen easily, the S3pro results are the brightest (plus different WB), the X-E1 comes second and the 5dII is darkest. In other words, with the same ISO setting the S3pro is the most sensitive, the Canon 5dII the least sensitive.

If you look on, where Fuji S3pro and 5d II have been tested my captures confirm their measurings for both cameras, more or less: The S3pro on measures as one of probably very few cameras who's ISO settings are very, very precise, almost a reference, whereas Canon's 5dII does cheat quite a bit, actually 2/3 of a stop. So, my overview suggests that Fuji's X-E1 should lie somewhere in the middle between the Canon and the S3pro, around 1/3 of a stop too optimistic maybe even a bit less.

Quite ok in my opinion, I would have thought it is much worse.

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'All the technique in the world doesn’t compensate for the inability to notice.' (Elliot Erwitt)

Excellent post Bernie and very interesting.

I agree, 1/3 of a stop is perfectly fine, no big deal at all.


 BillyInya's gear list:BillyInya's gear list
Nikon D7000 Fujifilm X-E1 Nikon AF-S DX Nikkor 18-135mm f/3.5-5.6G ED-IF Nikon AF-S DX Nikkor 17-55mm f/2.8G ED-IF Nikon AF-S Nikkor 70-200mm f/2.8G ED VR II +8 more
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