Is Pentax cheating at high ISO? DPReview tests suggest this is the case...

[996GT2]

http://www.dpreview.com/reviews/canoneos60d/page17.asp

If you go here and look at EXIF data for the D7000 and K5 samples images at the same ISO, you'll see an interesting phenomenon. I've copied the EXIF data for ISO 6400 and 12800 below:

It seems like Pentax is "cheating" their ISO sensitivities by a whole stop. The D7000 has the same sensor but is using a shutter speed that is twice as fast when the aperture and ISO are held constant. DPReview is supposed to have a very consistent testing setup, so I don't think the lighting would have changed between shots. The only explanation left is that the K5's ISO sensitivities are off by as much as a whole stop.

What do you guys think?


ISO 6400:
Camera Maker: NIKON CORPORATION
Camera Model: NIKON D7000
Lens: 50.0 mm f/1.4
Image Date: 2010-11-12
Focal Length: 50mm (35mm equivalent: 75mm)
Focus Distance: 1.19m
Aperture: f/9.0
Exposure Time: 0.0006 s (1/1600)
ISO equiv: 6400
Exposure Bias: none
Metering Mode: Matrix
Exposure: Manual
Exposure Mode: Manual
White Balance: Manual
Flash Fired: No
Color Space: Adobe RGB (1998)

Camera Maker: PENTAX
Camera Model: PENTAX K-5
Lens: smc PENTAX-FA 50mm F1.4
Image Date: 2010-11-11
Focal Length: 50mm (35mm equivalent: 75mm)
Aperture: f/9.0
Exposure Time: 0.0013 s (1/800)
ISO equiv: 6400
Exposure Bias: none
Metering Mode: Matrix
Exposure: Manual
Exposure Mode: Manual
White Balance: Manual
Flash Fired: No
Color Space: sRGB


ISO 12800:
Camera Maker: PENTAX
Camera Model: PENTAX K-5
Lens: smc PENTAX-FA 50mm F1.4
Image Date: 2010-11-11
Focal Length: 50mm (35mm equivalent: 75mm)
Aperture: f/9.0
Exposure Time: 0.0005 s (1/2000)
ISO equiv: 12800
Exposure Bias: none
Metering Mode: Matrix
Exposure: Manual
Exposure Mode: Manual
White Balance: Manual
Flash Fired: No
Color Space: sRGB

Camera Maker: NIKON CORPORATION
Camera Model: NIKON D7000
Lens: 50.0 mm f/1.4
Image Date: 2010-11-12
Focal Length: 50mm (35mm equivalent: 75mm)
Focus Distance: 1.19m
Aperture: f/9.0
Exposure Time: 0.0003 s (1/3200)
ISO equiv: 12800
Exposure Bias: none
Metering Mode: Matrix
Exposure: Manual
Exposure Mode: Manual
White Balance: Manual
Flash Fired: No
Color Space: Adobe RGB (1998)

 

[speedy2]

Interesting. Stick a high ISO number out there and hope no one notices? Who cares. You bump the ISO and you have to use a slower shutter. I haven't seen any Pentax ads, but I wonder if they boast about their ISO.

 

[Cattykit]

Interesting find but I'm not sure what's going on there. Notice how manual exposure setting was used on both cameras. The shooter intentionally chose different shutter speed and I wonder why. If it was to compensate difference in exposure, he should have made a note yet he did not. I find that strange.

Go to http://www.dxomark.com/index.php/en/Camera-Sensor/Compare-sensors/%28appareil1%29/675|0/%28appareil2%29/680|0/%28appareil3%29/676|0/%28onglet%29/0/%28brand%29/Sony/%28brand2%29/Nikon/%28brand3%29/Pentax , and check out ISO sensivity ratings there. Of all those cameras that use same sensor, Pentax is acutally the most accurate one.

 

[ElFenix]

Interesting find but I'm not sure what's going on there. Notice how manual exposure setting was used on both cameras. The shooter intentionally chose different shutter speed and I wonder why. If it was to compensate difference in exposure, he should have made a note yet he did not. I find that strange.

according to dpreview they set the cameras so they get the same exposure on middle gray. which makes no sense for a noise test.