All Forum Comments
Comment by ChrisA posted on Question for Matt on M/K lens metering at 05/04/2007 - 12:40
Quote:
So, I compared the Green Button (GB) with Optical Preview (OP) and noticed these variances:
When using OP along with small apertures (large f-numbers) and low level lighting the exposure display will flash. If it flashes the exposure will be wrong. The GB doesn't show this.
When I compared GB with OP (all just with the K10D), I found that GB set the shutter speed, whereas OP did not - it just showed you in the display how many stops over or under you were, and left you to manually set the shutter speed.So, I compared the Green Button (GB) with Optical Preview (OP) and noticed these variances:
When using OP along with small apertures (large f-numbers) and low level lighting the exposure display will flash. If it flashes the exposure will be wrong. The GB doesn't show this.
However, once you'd done this, my observation was that the "correct" shutter speed for the set aperture was the same whether metered and set with GB, or metered with OP and set by me.
"Correct" as in "not showing under or over", but still wrong compared with wide open metering with the lens in A mode.
Is this different from your findings?
Comment by ChrisA posted on Question for Matt on M/K lens metering at 05/04/2007 - 11:24
Quote:
because the meter cells are in the pentaprism housing, so the light they look at goes through the screen.
Ok, so how do the meter cells know whether the lens is stopped down, or wide open with lower ambient light levels?because the meter cells are in the pentaprism housing, so the light they look at goes through the screen.
Comment by ChrisA posted on Question for Matt on M/K lens metering at 03/04/2007 - 16:53
Sorry to break in here with what must be a really dumb question...
Why does the screen have anything at all to do with the metering?? :
Why does the screen have anything at all to do with the metering?? :
Comment by ChrisA posted on Question for Matt on M/K lens metering at 03/04/2007 - 16:15
Quote:
Yes, given that it works OK with all lenses when set to A, that suggests it is not a focussing screen problem but a software problem.
Absolutely.Yes, given that it works OK with all lenses when set to A, that suggests it is not a focussing screen problem but a software problem.
Not only does it work with A lenses set to A, it does not work with the same A lenses when not set to A, in other words, when using stop down metering to set the shutter speed.
Comment by ChrisA posted on Question for Matt on M/K lens metering at 03/04/2007 - 14:53
Quote:
Apologies to Chris, incidentally, for suggesting he was doing something wrong.
No problem, George. It was a while before I was convinced that it wasn't finger trouble myself. Apologies to Chris, incidentally, for suggesting he was doing something wrong.
Unlike the software industry, where it's to be expected that new releases will be buggy, I think we kind of expect cameras to work. So I'm not surprised that there was a certain amount of scepticism.
Quote:
My question is, is this something that is likely to be controlled by firmware, and therefore fixable, or is it controlled by a lower level of software which can't be updated?
Very much the question in my mind too.My question is, is this something that is likely to be controlled by firmware, and therefore fixable, or is it controlled by a lower level of software which can't be updated?
There's a tantalising hint in the post from Chris@SRS after he met up with a rep...
https://www.pentaxuser.com/forum/viewtopic.php?t=4185
It would make the K10D even closer to perfect if this could be fixed.
Comment by ChrisA posted on Question for Matt on M/K lens metering at 02/04/2007 - 17:22
All this does beg the question as to why it is that the K10D, and, it would appear, other Pentax AF cameras, seem to be able to use LPs perfectly well.
It seems that many others must not be able to, given that so many references are unequivocal in their insistence that CPs are required for AF cameras.
It seems that many others must not be able to, given that so many references are unequivocal in their insistence that CPs are required for AF cameras.
Comment by ChrisA posted on Polarisers at 31/03/2007 - 15:28
Quote:
"Testing for Linear Polarizer Compatibility
It's easy to test your camera's LP compatibility, at least with regard to metering:
Mount the LP and fill the viewfinder with a large dull light-colored surface like an indoor wall.
Make sure no specular reflections, atmospheric scatter or other polarized light sources reach the camera during the test.
Under constant lighting, turn on the LCD and watch the exposure settings as you rotate the polarizer.
If the exposure settings change significantly over any 180° rotation of the polarizer ring, your camera requires a CP."
Thanks for noting this. And thanks to Galoot for posting the link (at which is also www.dpfwiw.com/polarizer.htm#circular, which has the LP test on it that RF mentions). Very pleased to report that my K10D passes this test. So I'll stick with my linear polarisers "Testing for Linear Polarizer Compatibility
It's easy to test your camera's LP compatibility, at least with regard to metering:
Mount the LP and fill the viewfinder with a large dull light-colored surface like an indoor wall.
Make sure no specular reflections, atmospheric scatter or other polarized light sources reach the camera during the test.
Under constant lighting, turn on the LCD and watch the exposure settings as you rotate the polarizer.
If the exposure settings change significantly over any 180° rotation of the polarizer ring, your camera requires a CP."
Quote:
Also remember that if your lens is not of IF type then as you focus the degree of polarization will change and have to be re-adjusted after focusing. This is due to the front focusing ring rotating.
Ah yes indeed.Also remember that if your lens is not of IF type then as you focus the degree of polarization will change and have to be re-adjusted after focusing. This is due to the front focusing ring rotating.
The Sigma 28-200 I've used for years has a rotating front end, and its a right pain to constantly readjust the polariser. The Pentax one I've just acquired is IF, so another bonus!
Comment by ChrisA posted on Polarisers at 31/03/2007 - 11:09
Quote:
From what I can find out the auto-focus issue is less of a problem than exposure. Linear filters can cause 2-3 stops under exposure in some cases depending on the exact nature of the metering system.
What's happening with your exposures?
Thanks. I'll have a look tomorrow sometime and report back...From what I can find out the auto-focus issue is less of a problem than exposure. Linear filters can cause 2-3 stops under exposure in some cases depending on the exact nature of the metering system.
What's happening with your exposures?
Comment by ChrisA posted on Polarisers at 31/03/2007 - 00:38
Ok, Captain's log, supplemental...
Just to assault received wisdom even further, I've had a rummage in my camera bag, and extracted my old Cokin filters.
Amongst which is one labelled 'P 160 Pola'
On its box it says "Linear Pola".. and to confirm this, a moment on the Cokin web site yields this:
http://www.cokin.com/ico3-p1-7.html
Clearly, the 160 is the linear, and the 164 is the circular.
With the 160 on the front, the AF still works.
So. What is the issue with the two different types, and AF as opposed to MF cameras?
Just to assault received wisdom even further, I've had a rummage in my camera bag, and extracted my old Cokin filters.
Amongst which is one labelled 'P 160 Pola'
On its box it says "Linear Pola".. and to confirm this, a moment on the Cokin web site yields this:
http://www.cokin.com/ico3-p1-7.html
Clearly, the 160 is the linear, and the 164 is the circular.
With the 160 on the front, the AF still works.
So. What is the issue with the two different types, and AF as opposed to MF cameras?
Comment by ChrisA posted on Polarisers at 31/03/2007 - 00:13
Further, it'd be interesting to see how it compares when using, say an fixed f/8 telephoto. I can set up the experiment, but I just don't have the gear anymore...
If you mean compare the fixed (ie wide open) F8 exposure with that, with that obtained with F8 set on a non-A, manually metered lens, I could check that quite easily.