Canon's 18mp Sensor

Started Jul 14, 2012 | Discussions thread
KLO82
Contributing MemberPosts: 717
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Re: You're right.
In reply to TrojMacReady, Jul 18, 2012

TrojMacReady wrote:

The difference in lighting would not matter as long as they are determining exposure by their same Sekonic (incident) light meter.

I agree if the illumination of the scene would already be equally spread, but seeing as the top is sometimes darker than the bottom, vice versa, etc., that doesn't seem to be the case either. And overall it can result in differing shutterspeeds, thus making it impossible for us to judge sensitivity differences by just looking at the exposure settings.

As long as they are using same light meter to detemine exposure and shoot accordingly, we do not have to consider the difference in shutter speed or f number. For example, say their light meter showed that exposure needed for ISO 100 was f5.6, 1/250 sec, and they shot accordingly to that. After some time, they have completely changed the lighting during testing of another camera. This time, the meter showed that for ISO 100, the settings needed are f5.6, 1/100 sec (due to decrease in light intensity in this case). In both cases, the exposure should be same [same amount of light per unit area should reach the sensor, not considering difference in t stops and stated and actual shutter speed]. But where they mix up is, when they find some camera does not show 18% gray card as mid gray in sRGB output, they disregard the meter reading and increase/ decrease the shutter speed (or f number) to make the gray card as mid gray in jpeg - and note how much they had to compensate and based on that they announce the camera has "overstated" or "understated" ISO. If they would stick to the shutter speed and f number setting according to the meter reading, the comparisons would be fair.

But you are of course correct about the not equally spread lighting will ruin the tests.

But in case of IR, they just rely on camera's internal light meter. SO we can not even get any idea how much diferrence in exposure is there between two cameras.

With constant light levels and for cameras with exposures that are close or identical, atleast certain comparisons can give us an idea of how they compare. With results usually in line with DXO measurements and vice versa.

IR changes lighting, AFAIK, and does not use light meter - they rely on the cameras built in light meter. Different cameras have differently calibrated meters - just like their ISO speed settings. Some other dpreview forum member previously posted email communication with them - they confirmed that they do not keep the light level constant. So in this case, we do not have any idea what is the difference of exposure between the cameras!

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