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08-21-2009, 06:59 AM - 1 Like   #106
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QuoteOriginally posted by taveren Quote
I too was unimpressed that you couldn't turn off the dark frame noise reduction in the K-7 but I bought one anyways. I do a great deal of long exposure night photography and waiting is a bit annoying, but the results are still amazing. If you can live with it, the K-7 is an excellent camera for night time shoots.

Here's a couple recent examples:



Why not utilise stacking to get around DFS?

Hopefully pentax will fix this with a firmware update.

08-21-2009, 07:11 AM   #107
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QuoteOriginally posted by C.W Tsorotes Quote
Why not utilise stacking to get around DFS?

Hopefully pentax will fix this with a firmware update.
Because that's more work later, and sometimes when following star trails, stacking will show if you miss even a few millseconds between shots. Tripod could move if on an uneven base in the middle of your multiple shots etc etc. Just saying that if you can live with it, it takes amazing long exposures anyways.
08-21-2009, 07:54 AM   #108
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QuoteOriginally posted by taveren Quote
Because that's more work later, and sometimes when following star trails, stacking will show if you miss even a few millseconds between shots. Tripod could move if on an uneven base in the middle of your multiple shots etc etc. Just saying that if you can live with it, it takes amazing long exposures anyways.
True true.

How mucch does it effect the image without DFS?
08-21-2009, 08:25 AM   #109
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Can somebody please do the following experiment:

1. one long exposure at 4:30 min (ISO 1600) in bulb mode
2. a multi exposure, 9 images, auto-EV compensation, 30s each, no bulb mode(consecutive exposures using a remote).

And provide the two respective RAW files.

I am really curious to see how much impact DFS (the only difference between #1 and #2) really has.

Maybe, if the impact is marginal, we can convince Pentax to make DFS optional for at least up to 5 minutes.

08-21-2009, 08:35 AM   #110
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QuoteOriginally posted by C.W Tsorotes Quote
ISO100 and 71mins in pitch black
I pushed your image to ISO 25600 (+8EV) and it is free of artifacts. No banding whatsoever, no magenta edge tint or glow This is stunning even for a 1s exposure, let alone a 4260s exposure ...

(note: I assume the small stripe at the left edge is from a real object, like a door frame).

Last edited by falconeye; 06-15-2011 at 05:29 AM.
08-21-2009, 03:06 PM   #111
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QuoteOriginally posted by falconeye Quote
I pushed your image to ISO 25600 (+8EV) and it is free of artifacts. No banding whatsoever, no magenta edge tint or glow This is stunning even for a 1s exposure, let alone a 4260s exposure ...

(note: I assume the small stripe at the left edge is from a real object, like a door frame).
Yes it's all objects in the room.
08-21-2009, 03:29 PM   #112
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Should say when I brought the original raw into PS it had quite a few hot pixels initially but taken care of by Camera Raw.

I was suprised by how warm the camera got to, but yes very suprised with how good it turned out.

I have a theory maybe the K7 needs a bit of break-in time to perform, because I'm finding it a lot less noisy now after more use than when I first got it.
08-22-2009, 07:36 PM   #113
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Anyone else done any long exposure shots with the K7?

08-23-2009, 06:25 PM   #114
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QuoteOriginally posted by C.W Tsorotes Quote
...
I was surprised by how warm the camera got to, ...
If you search this forum for my updated list of power measurements you will find the K100D draws a lot of power while you expose the sensor.

When exposing it draws 606 ma at 6.5 volts which equals 4.0 watts. That is a lot of heat contained inside the moderately air tight shell. To do long exposures astro cameras provide a means to get heat out of the body either by fans, heat sinks, and/or solid state heat pumps (Peltier cells). Cameras designed for daytime use (short exposures) build up heat which increases noise.

My K110D is dedicated to astronomy (9400 long exposure frames so far!) and I let it cool down a little between frames.
08-24-2009, 08:07 AM   #115
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I've found the best way to do long exposures without heat problems is to shoot in Winter. Camera doesn't get too hot when it's -30C.
08-31-2009, 12:47 PM   #116
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QuoteOriginally posted by Entropy Quote
The K10 does have automatic DFS, and it is on by default.

The problem is that in the K20 and later, it becomes *forced* automatic DFS. For K10, the options are something like "Auto/off" or "On/Auto/Off".

In K20 and K-7, it becomes "On/Auto". The issue people have here is that there is no "Off" any more.
Ok, thanks. Guess I haven't been by the details in the manual.



I was btw, just reading a book about National Geography photographers :
Moonlight is a favorite source of illumination for space photographer Roger H. Ressmeyer, who also works with long exposures at night. “I feel I’m returning to photographers roots. Back in the early 1800s it could take minutes or even hours to take a picture by sunlight“

Ressmeyer’s photographs of science and technology are often grand productions. When possible, he plans everything precisely. He pays attention not only to the timing of an eclipse, for instance, but to the sky positions of galaxies and individual stars. “To cover my bases, I may set up ten or twelve cameras to take pictures simultaneously with different exposures. If I’m doing a two-hour shoot that ends with a moonrise, I can’t do it twice.”






QuoteOriginally posted by C.W Tsorotes Quote
Another experiment.

F20, ISO100 and 71mins in pitch black. Shot in raw, suprisingly quite noise free, camera was very warm.

There was no extra NR applied.

This is a cool looking photo
11-12-2009, 02:47 PM   #117
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Updates on this Issue

Hi everybody,

I've been reading this forum for a while, but just decided to join. I'm currently a K10 user, and have been strongly contemplating upgrading to a K-7.

This mandatory noise reduction issue in (30 seconds+ in Bulb mode) is the one thing that's making me think twice, though. Although I don't do all that much Bulb shooting, I can see it being a huge issue for times that I do use it.

Does anybody know if Pentax plans on changing the firmware? Should I wait until the K-8?

Thanks,
Bryan Scott
11-13-2009, 12:56 PM   #118
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Thanks guys, this thread was very informative. I had been considering the Kx or saving up a little more for the for the K7 and although I dont shoot a huge amount of long exposures, not being able to disable DFS really annoys me. I could just about forgive it in a camera like the Kx, but the K7? I am annoyed now, I just bought another lens to go on my K100D and was planning a new body after Christmas, specifically because I am unhappy with the performance of the K100D with long exposures. I had thought that image stacking with the Kx would be a way to get long exposures without shelling out for the K7, but there is no real interval shooting. The K7 will do interval shooting, but still insists on DFS for bulb exposures (hardly advanced control for the user). The Kx has the DFS issue, but no connectors for interval shooting (expected I guess, as Pentax consider this a beginners camera). If this is the way the cameras have operated since the K20, it is unlikely to be something Pentax will change in firmware and I don't feel like hanging about in the hope that another body might suddenly appear that has a bit of flexibility.
11-14-2009, 08:32 PM   #119
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I agree that I would not plan on Pentax, "fixing the firmware." When the first CMOS sensor Pentax came out many on this Forum thought forced NR for long exposures was an oversight. I suspected it wasn't, the first Canon CMOS sensor cameras had forced NR as well. Many reported it to Pentax assuming it would be fixed quickly. They have ignored the pleas ever since.

I'm happy with my K1x0Ds where I'm in control even though usually I enable internal NR which works better for me then subtracting my own dark frames.
11-16-2009, 05:28 AM   #120
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QuoteOriginally posted by ambienthousewife Quote
not being able to disable DFS really annoys me. I could just about forgive it in a camera like the Kx, but the K7? I am annoyed now
Without the (forced) DFS, you would be very annoyed by the high amount of noise. Circuitry thermal noise is still an issue with CMOS sensors and long exposures.
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