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07-12-2009, 06:03 AM   #1
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The K7 and long exposures

I've been reading a lot of messages about the K7 and it seems like a love-in fest.

But I haven't read a single report about the K7's long exposure ability.

Is there anyone in this forum, who owns a K7, and has an interest in long exposures? That is, bulb mode and exposures longer than 1 minute.

As I am sure some of you are aware, I have 'occasionally' complained about how poor the K20D performs when taking long exposures. There is a fair bit of noise but the worst issue is the forced DFS (Dark Frame Subtraction). If only Pentax, at a minimum, would modify the firmware to do delayed DFS. Let me take all my exposures now... then do the DFS later.

Anyhow, I am considering an upgrade to the K7 but only if DFS can be turned off. Besides, software (i.e. Stacker) DFS is almost always better anyway.

Anyone test the K7's long exposure [bulb] mode yet?

Thank you for your input. :-)


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07-12-2009, 06:42 AM   #2
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The K-7's long-exposure NR using DFS can be turned off for exposures less than 30 seconds.
More than 30 seconds it kicks in by itself - you can't turn it off.

I use the K100D for long exposures - its still the best Pentax body I've tried for long exposures.
At this point of technological development, I think you just aren't going to get low noise long exposures > 30 seconds from a 14 MP APS-C sensor.

I might try some moon-light shots using the K-7 on the next full-moon, good weather permitting.
We're just a few days past the full moon, but I've got other priorities for trying out the K-7 right now.
07-12-2009, 07:05 AM   #3
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QuoteOriginally posted by kittykat46 Quote
The K-7's long-exposure NR using DFS can be turned off for exposures less than 30 seconds.
More than 30 seconds it kicks in by itself - you can't turn it off.

This is crazy! So it kicks in by itself just about when you start getting unbearably long waiting times until you can take the next photo! On a semi-pro camera this should really be the photographer's choice...
07-12-2009, 05:52 PM   #4
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QuoteOriginally posted by Jimfear Quote
This is crazy! So it kicks in by itself just about when you start getting unbearably long waiting times until you can take the next photo! On a semi-pro camera this should really be the photographer's choice...
I agree - it's awful, but so is the noise from long exposures on these cmos chips I guess. Now that I'll have a K7 soon, I'm strongly considering selling the K20D and getting a K10D for night photography.

The K200D I used to have kicked the K20d's butt on long exposures - very disappointing . (of course if the k7 30 sec. exposures look ok, I'll probably just look into stacking 'em).

07-12-2009, 07:07 PM   #5
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I may have what you are looking for.

Last thursday I tried to get an image of the space station passing over.

I don't know what went wrong but I never saw it during the 6 minute period it was supposed to be visible in my area.

A little over 6 minutes at ISO 100 with my 28-75 F2,8 at F8

shot was JPEG maximum quality. How much of the image do you want to see and at what resolution
07-12-2009, 07:30 PM   #6
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QuoteOriginally posted by Lowell Goudge Quote
I may have what you are looking for.

Last thursday I tried to get an image of the space station passing over.

I don't know what went wrong but I never saw it during the 6 minute period it was supposed to be visible in my area.

A little over 6 minutes at ISO 100 with my 28-75 F2,8 at F8

shot was JPEG maximum quality. How much of the image do you want to see and at what resolution
You must have missed it.

Apparently, it's visable in the daylight (sometimes) if you know where to look:

ISS tracks over DC - tough to see - was very faint by cameraperson : Weather Underground

ISS tracks over DC - easier to see - NEGATIVE by cameraperson : Weather Underground
07-13-2009, 12:33 AM   #7
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The Dreaded Long Exposure of K7

Hi everybody,
I have just bought the K7 up graded from my trusty K20D on JCPENTAX's recomendation that the ICNR could be turned off completly and He made that point quite strongly. It appears that he is 100% wrong. In the Bulb setting any time exposure will bring in ICNR wheather it is turned off or not.
I've actually bought 2 cameras and they are both the same.
Don't get me wrong the K7 is a top camera and I can't fault the video quality, great balance, good feel but for astrophotography to do your own dark frames
(that's if you need them) it falls in a heep.
Come on Pentax far go.
07-13-2009, 12:57 AM   #8
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some night shots with K7:

I think they looks great:

https://www.pentaxforums.com/forums/post-your-photos/63698-k-7-v1-00-iso-test...age-laden.html

07-13-2009, 06:01 AM   #9
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QuoteOriginally posted by Duck Dodgers Quote
I am wondering, and have not gone back to the schedule for my area since, but I might have gotten the time incorrect, i.e. daylight savings vs standard time. Having said that, in looking at my shot, there is one intermittent trace, about the same length as the 6 minute star trails, but this can;t be the space station. It was supposed to "rise" in the wsw sky at 10 degrees, achieve a peak of 50 degrees and "set" in the nw sky at 10 degrees, all within 6 minutes. I was hoping to capture an arc in the sky from the trrail

Aside from my obvious scheduling error, yes there is a lot of noise in the black it is especially obvoius when you try to boost the background sky (about 5 greyscale in my shot) up to the middle of the exposure range. It just goes to show you can't make something from nothing.

in reality, I believe good low ISO film is the best for these shots, not counting for the lack of instant gratification.

one thing that puzzles me is the comment from the OP, about being stuck with the noise reduction. I believe it is an option on every DSLR to shut this off, certainly on my *istD, K10 and K7 it is.
07-13-2009, 06:38 AM   #10
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QuoteOriginally posted by Lowell Goudge Quote
...

one thing that puzzles me is the comment from the OP, about being stuck with the noise reduction. I believe it is an option on every DSLR to shut this off, certainly on my *istD, K10 and K7 it is.
On the K20D, the dark frame subtraction is mandatory for exposures longer than six seconds or so - you can't turn it off . Now hearing from cyclone that it's mandatory in bulb mode on the k7 is a bit disheartening.
07-13-2009, 06:52 AM   #11
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Wow! I really hope you're wrong about the forced DFS

QuoteOriginally posted by kittykat46 Quote
The K-7's long-exposure NR using DFS can be turned off for exposures less than 30 seconds.
More than 30 seconds it kicks in by itself - you can't turn it off.
I hope you are wrong. If you're not, this is very disappointing news and Pentax did not listen to many complaints and bad reviews they received, in regards to the K20D! This will also mean that I will have to drop Pentax for good. It makes no sense to carry two separate lens formats... or borrow a Canon when I need to do long exposures (not just astrophotography).

The amount of time I have wasted, just waiting for the DFS on my K20D has been ridiculous.

QuoteOriginally posted by kittykat46 Quote
At this point of technological development, I think you just aren't going to get low noise long exposures > 30 seconds from a 14 MP APS-C sensor.
But that's not the point. Every other manufacturer allows their owner the option of doing there own DFS. If what you say is true, Pentax may still have some serious problems with sensor noise and they feel the need to hide it behind a forced DFS. Like I have stated a million times, only Pentax does this!

QuoteOriginally posted by kittykat46 Quote
I might try some moon-light shots using the K-7 on the next full-moon, good weather permitting. We're just a few days past the full moon, but I've got other priorities for trying out the K-7 right now.
Well, I am sure they will be nice but this won't test the long exposure ability of the K7.

Thanks for the bad news.
07-13-2009, 06:57 AM   #12
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QuoteOriginally posted by Jimfear Quote
This is crazy! So it kicks in by itself just about when you start getting unbearably long waiting times until you can take the next photo! On a semi-pro camera this should really be the photographer's choice...
Exactly!

Using the K20D for long exposures is unbearably annoying. It's not just astrophotography that is affected. What if you want to capture the city nightlife, movement of cars on a highway, or how about lightning?

Every exposure is doubled because of the forced DFS!

With any other camera, you take your exposures.... then take a few dark frames later on when you have the time and apply them to the long exposure frames using computer software. That is, only if you find the noise unacceptable. At least, you have the choice on any other camera.
07-13-2009, 07:09 AM   #13
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But I think you are missing the point of this thread. We are discussing long exposures and whether or not the in camera DFS can be disabled. So far, it appears that little has changed with the K7, when compared to the K20D.

Those photos (in your link) also demonstrate that the K7 may actually use the same sensor as the K20D. Because they appear awfully similar to K20D photos.

So, is the K7 just a repackaged K20D with a few new bells and whistles? Wow, it looks like Christmas is over!
07-13-2009, 07:14 AM   #14
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QuoteOriginally posted by Lowell Goudge Quote
one thing that puzzles me is the comment from the OP, about being stuck with the noise reduction. I believe it is an option on every DSLR to shut this off, certainly on my *istD, K10 and K7 it is.
Well, it should be optional on every DSLR. However, this is not the case with the K20D. It is not optional on ANY exposure taken for ANY length of time in bulb mode.

Now, I am surprised about your K7 comment. Everyone else is stating that the K7 also forces DFS on every bulb exposure. Are you sure about this?
07-13-2009, 07:28 AM   #15
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QuoteOriginally posted by pentaxmz Quote
Well, it should be optional on every DSLR. However, this is not the case with the K20D. It is not optional on ANY exposure taken for ANY length of time in bulb mode.

Now, I am surprised about your K7 comment. Everyone else is stating that the K7 also forces DFS on every bulb exposure. Are you sure about this?
what seems interesting is that it is only applied in Bulb, not manual. I could take a 30 second exposure in manual and get the confirmation image immediately, but a 25 second in Bulb took 20 seconds to appear regardless of noise reduction being on or off.

it seems that slow speed shutter noise reduction is not the same as DFS.
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