Re: Canon Response to 5D Dark Corners

Kennedy McEwen <rkm@xxxxxxxxxxxxxxxxxxxx> wrote:

But you didn't simulate the light that falls on the sensor from a lens.

Exactly, because the argument that you have made is that it isn't the
lens that causes the problem, but that the *sensor* somehow has a
different response to angle of incidence than film has.

It's not the argument I have made; it's the argument I have thus far
accepted. There is a distinction. I cannot prove it. I go on the
statements of people who know more about it than I do, mixed in with
simple observation.

So the test attempted to measure how different that response actually
is in a real sensor. Whether the light comes from a lens, the sun or
a point source is irrelevant.

Why? The light is falling on the sensor entirely differently in your
test than it does in actual usage. Yes, your test eliminates the effect
of falloff from the lens, but it does so by changing too many variables
for me to accept it as valid, when observation shows something else.

Eliminate lens falloff by comparing a shot on film using the same lens.
We *know* there is falloff in wide-angle lenses (especially), and we know
why it happens, so its effect can be subtracted from a test by changing
only the variable we're trying to test -- the sensor.

The light hitting a pixel on the sensor is not all coming from the same
angle, in actual usage. The angle varies; you know this. So, in order
to accept your results I'd like either an explanation, from a sensor
design perspective, of why this doesn't matter with regard to the problem
at hand (angle of incidence), or I'd like a test that doesn't change that
fact, done using a lens.

Your, and others, argument has been that there is a fundamental angular
response variation in the sensor. The test proved that if there is it
is irrelevant and that essentially *all* of the light fall off at the
edges and corners of the field *MUST* be due to the lens and therefore
no worse on full frame dSLRs than it was in full frame film dSLRs.

Except that simple observation says otherwise -- the problem appears to
be more pronounced with digital than with film. And everyone has been
saying that the angle of incidence has more effect with digital than
with film, which nicely matches up with real-world observation. Your
test has not convinced me otherwise.

Yes it is - a point source placed a significant distance from the focal
plane ensures that ALL of the light is incident at every pixel on the
focal plane at almost the same angle.

But that's exactly my point. This doesn't happen in real-world usage
with a lens, and thus we have another change between the test and the
real world, which has not been accounted for in the test.

However the question is how much of that is due to the lens (and
therefore common to the format, whether film or digital) and how much
is due to the angular sensitivity of the sensor (and therefore possibly
different between film and digital on the same format).

So why not compare film with digital on the same format?

Since you have consistently argued that the sensor is somehow defective,
it is clear that you don't understand the problem or its cause!

Not defective, but simply different.

If the contention is that the difference between film and digital causes
the visible effect, the valid test is film versus digital, not something
else entirely; you've tested something else entirely, with no justification
to discount the additional variables.

--
Jeremy | jeremy@xxxxxxxxxxx
.

Relevant Pages

  • Re: Light fall off on dSLRs - an experiment
    ... Interesting results and they seem to differ considerably from mine which I have just repeated over a range of angles to get more of a response map with azimuth and elevation angle of the light source relative to the pixels. ... I managed to do this by temporarily fitting a lens to the camera body and then just aligning it so that the light source was exactly on the central focus marker. ... I wonder if this is just due to a different sensor - it is dramatically different from my results which have a much flatter response. ...
    (rec.photo.digital.slr-systems)
  • Re: Nikon D40 with 300mm lens AND teleconverter (Nikkor AF-S Teleconverter TC-20E II)
    ... 24mm lens. ... But it does if you specify the sensor size as well. ... think I could figure out the angle of view given a focal length, ... In the simple standard case of a lens producing a rectilinear image ...
    (rec.photo.digital.slr-systems)
  • Re: Canon Response to 5D Dark Corners
    ... as extreme an angle of incidence as the Canon lens mount permits. ... There was essentially no difference in sensor sensitivity between these ... But you didn't simulate the light that falls on the sensor from a lens. ... Exactly, because the argument that you have made is that it isn't the lens that causes the problem, but that the *sensor* somehow has a different response to angle of incidence than film has. ...
    (rec.photo.digital.slr-systems)
  • Re: Light fall off on dSLRs - an experiment
    ... incidence on a dSLR then propose it. ... element closest to the sensor.. ... and suitable wide angle, I can't do that. ... from various areas of the lens will actually *hit* the sensor from ...
    (rec.photo.digital.slr-systems)
  • Re: Which digital SLR system?
    ... I recommend you get the camera you like, decent lenses, and learn the zen of ... If you enter digital photography the quality of the lens, ... is not as absolute a value as with film based ... sensor as much or more than what the lens produces on the sensor. ...
    (rec.photo.digital.slr-systems)
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