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12-21-2010, 02:05 PM   #1
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I want digital neutral filter in my k-5, so ...

neutral filter can sometimes be usefull function in the camera. You can set long time exposure without changing aperture. I think it costs nothing to add this function to camera's software. how do you think, who should i contact to present idea like this? is there any feedback unit in Pentax? I just want my camera to be better.

12-21-2010, 02:31 PM   #2
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you can't reproduce that with software since it is directly related to exposure and CMOS sensitivity.
you need to buy ND filter or camera with minimum ISO rating lets say 6
12-21-2010, 02:41 PM   #3
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I have used Hoya PRO 1 Digital filters ND8 and ND4 with good results.
12-21-2010, 02:56 PM   #4
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QuoteOriginally posted by acheron Quote
you can't reproduce that with software since it is directly related to exposure and cmos sensitivity.
You need to buy nd filter or camera with minimum iso rating lets say 6
+1

2345678

12-21-2010, 03:22 PM   #5
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QuoteOriginally posted by Acheron Quote
you can't reproduce that with software since it is directly related to exposure and CMOS sensitivity.
you need to buy ND filter or camera with minimum ISO rating lets say 6
Well, you can, actually.
At least with my K20d, but I'd be surprised if it wasn't the same with a K5.

Just select an exposure, then set multi-exposure on and select the number of shots to be taken (2 to 9 on the K20d), then select also the "Auto EV adjust" check box.

What did you meter? 1 sec @ f/2.8?
At f/16 it'd be 30". Make it so.

If you selected 9 multiple shots the camera will shoot nine 30-seconds (270" or 4 minutes and a half) shots and average out the exposure as well, giving you basically a 9X ND filter.

Try it.
12-21-2010, 03:26 PM   #6
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Implementing this in software would not work, I think, because after a pixel has reached its maximum capacity to register light it will not continue to register any more; in this sense the sensor is exactly like film, with too much light there is overexposure. Of course, the software could automatically adjust ISO downward (lower amplifier gain) and after hitting the limit with that maybe use a multiple short exposures during the nominal long exposure for an effect almost but not quite totally unlike an NDF :-)
12-21-2010, 09:48 PM   #7
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at 80iso the camera is probably using near zero amplification (or some minimum operating amount), merely reading out what is produced by the sensor itself. This is where the problem is.
12-22-2010, 02:08 AM   #8
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QuoteOriginally posted by jolepp Quote
...and after hitting the limit with that maybe use a multiple short exposures during the nominal long exposure for an effect almost but not quite totally unlike an NDF :-)
That's not what I was suggesting. I'm not saying to divide a 10 seconds exposure in 5 2 seconds ones. I'm saying that if you tick the "Auto EV adjust" check box the camera will average out the images, therefore obtaining the same result of an exposure as long as the sum of all the exposures made.

BTW this will also have a good effect on any digital noise you may have in dark areas, since the noise is randomly scattered and it will be smoothed over by the multiple exposure.

Actually this works better than a physical ND filter, since this kind of filters (at least the darker ones) often induce color dominants in the picture. To have a truly neutral ND filter you have by a quality, expensive filter.

12-22-2010, 03:37 AM   #9
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What I meant was really using a duty cycle in the exposure corresponding to to the degree of the filter, say for -2 stops 25% shutter open 75% shutter closed like so:

@0.000s : open shutter
@0.125s : close shutter
@0.500s : open shutter
@0.625s : close shutter
@1.000s : open shutter
@1.125s : close shutter
...
@9.625s : done
12-22-2010, 03:48 AM   #10
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QuoteOriginally posted by jolepp Quote
What I meant was really using a duty cycle in the exposure corresponding to to the degree of the filter, say for -2 stops 25% shutter open 75% shutter closed like so:

@0.000s : open shutter
@0.125s : close shutter
@0.500s : open shutter
@0.625s : close shutter
@1.000s : open shutter
@1.125s : close shutter
...
@9.625s : done
In fact that's simply a 2.5 seconds exposure diluted in 10 seconds. My solutions instead creates a real long exposure through the fusion of up to 9 shorter ones.

You've got to try it.
12-22-2010, 03:49 AM   #11
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QuoteOriginally posted by Huck Finn Quote
Well, you can, actually.
At least with my K20d, but I'd be surprised if it wasn't the same with a K5.

Just select an exposure, then set multi-exposure on and select the number of shots to be taken (2 to 9 on the K20d), then select also the "Auto EV adjust" check box.

What did you meter? 1 sec @ f/2.8?
At f/16 it'd be 30". Make it so.

If you selected 9 multiple shots the camera will shoot nine 30-seconds (270" or 4 minutes and a half) shots and average out the exposure as well, giving you basically a 9X ND filter.

Try it.
great, will try today when I get home from work
thanks
12-22-2010, 10:51 AM   #12
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Great trick! (the multiexposure) I'm going to use it for waterfall shots next summer! Makes it a lot easier to compose/focus without an ND on.
12-22-2010, 11:06 AM   #13
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QuoteOriginally posted by Huck Finn Quote
...
You've got to try it.
I have no particular application for an ND filter in mind at this time, but try to keep it in mind in case one turns up :-) Anyway, that multi-exposure-with-duty-cycle-variation idea popped up when I was trying to convince myself that an ND filter cannot be implemented in software; I suppose it kind of could like that, but wouldn't be quite the same, nor terribly useful.
12-22-2010, 12:46 PM   #14
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QuoteOriginally posted by Huck Finn Quote
Well, you can, actually.
At least with my K20d, but I'd be surprised if it wasn't the same with a K5.

Just select an exposure, then set multi-exposure on and select the number of shots to be taken (2 to 9 on the K20d), then select also the "Auto EV adjust" check box.

What did you meter? 1 sec @ f/2.8?
At f/16 it'd be 30". Make it so.

If you selected 9 multiple shots the camera will shoot nine 30-seconds (270" or 4 minutes and a half) shots and average out the exposure as well, giving you basically a 9X ND filter.

Try it.
Thanks.
Will try it soon. One query though. Is the multiple exposure photo RAW or Jpeg?
12-22-2010, 12:55 PM   #15
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QuoteOriginally posted by shadmanaj Quote
Thanks.
Will try it soon. One query though. Is the multiple exposure photo RAW or Jpeg?
I guess whatever you chose in your in-camera settings.
Personally I use RAW+.
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