[Digitalis]

An Open letter to major camera manufacturers has been issued on the LL due to the apparent discrepancies of the light loss from certain lenses and manufacturers bumping up the ISO -without the user being aware- to compensate for this loss of speed.

it makes for some interesting reading.

An Open Letter To The Major Camera Manufacturers


My personal thoughts in regards to pentax is that this would become painfully obvious is pentax was doing this behind the scenes ISO push. E.G: If a photographer using a M 50mm f/1.4 lens - with no electronic communication between the lens and body it would be impossible for the sensor's ISO to be increased because the camera has no idea of what aperture is being used. And if said photographer suddenly switched to a DA*55mm f/1.4 and noticed a difference in exposure/noise level then things would be looking fishy. As far as my experience goes I have heard reports of people experiencing differentials in exposure when they take their lenses off the A setting and controlling the aperture manually.For examples sake setting the aperture electronically to f/4 taking an image, and then repeating the process but manually setting the aperture to f/4 yields slightly brighter/darker images on certain lenses. Could this be evidence of this phenomenon?

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Last edited by Digitalis; 10-27-2010 at 04:53 PM.

[bobmaxja]

Another thread is already going on for this
https://www.pentaxforums.com/forums/pentax-news-rumors/120061-open-letter-maj...landscape.html

[Andrew Lang]

very interesting, I wonder if anyone will respond to it?

[Digitalis]

Another thread is already going on for this Open letter to the Major Camera Manufacturers by Lumionus Landscape

I am aware of that though I think the OP is asking the wrong question.

another thing I have noticed with the graph is that the cameras with the higher pixel density are performing the worst.

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Last edited by Digitalis; 10-27-2010 at 09:04 PM.

[alohadave]

I think that this paragraph is far more significant for most photographers:

One might be better off purchasing smaller aperture lenses and increasing the ISO. Since these lenses have much less light loss at the sensor, one may well end up with virtually indistinguishable results. In fact, is not even clear that large aperture lenses will deliver a shallower depth of field as intended. The DxO measurements to date prove that the marginal light rays just don’t hit the sensor. The point regarding depth of field is that these rays are also responsible for a larger blur spot when out of focus. If they are lost, they not only don’t contribute to the light intensity at the sensor, but they also don’t blur the out of focus planes as much as you would expect at wide apertures.

As for the auto adjustment of the ISO, I don't think it's really that big of a deal. For as sophisticated as dSLRs are, there is a fair bit of slop in the mechanical parts, especially with the aperture blades. Adjusting the ISO by less than a stop to compensate for the mechanical tolerances sounds like a pretty good idea. Ideally, the actual ISO value used would be reported in the exif data.