[falconeye]

My question is: Why don't manufactures give you a choice in the features to set up your shutter release on a 2 second timer that requires one press to engage the 2 second timer, and another press later when your exposure time has expired thus closing the shutter and completing your exposure?

Carl, the K-7 does it do so.

[pentaxmz]

i find it hard to beleive about the sensor temperature? surely if you do a 30 minute exposure followed by a 30 minute dark frame its no different to doing 2 30 minute exposures? therefore temps will be the same? or am i misunderstanding something here? (wouldnt be unusual!)

The point of the second equal exposure time (but dark) frame is for the camera's computer to do a comparative analysis of both exposures to find similarities (i.e. hot spots caused by sensor errors - usually due to heat).

We are not talking about huge (heat up your coffee) amounts of heat.

i guess the tradeoff for low noise in 'normal' pictures is high noise on long exposures
Thanks

Steve

No, not necessarily. Pentax just didn't have time/money/or inclination to fix the problems... It was ultimately a poorly designed Samsung imager.

[pentaxmz]

Carl, the K-7 does it do so.

How do you know? Where did you find this info?

The K-7 PDF manual doesn't seem to be published yet.

[DAVID564]

Let's face it if you want long exposures digital has a long way to go better to stick
with film.
however for reletively short exposures to 40 sec's "B" mode

I Have an old mechanical 120 Camera which has a "T" mode press once and the shutter opens press again and the shutter closes, perfect.

This mode not possible with 70's- 80's cameras as the move to electronics ment battery power, which could not keep a mirror up and shutter open for extended periods ?

however the recent (last ten years) advances in battery technology fuelled by the mobile
phone has revolutionised this field, perhaps its time to reinstate this long forgotten mode

[falconeye]

How do you know? Where did you find this info?

The K-7 PDF manual doesn't seem to be published yet.

I don't have the time to find it again for you. But I have a pretty good memory for such things. Just wait and see

P.S.
It probably was in any of those screenshots from the custom function section. Where you can set the remote trigger to act as OPEN when pressed first, then CLOSE when pressed again (since this isn't the default).

[5teve]

The point of the second equal exposure time (but dark) frame is for the camera's computer to do a comparative analysis of both exposures to find similarities (i.e. hot spots caused by sensor errors - usually due to heat).

We are not talking about huge (heat up your coffee) amounts of heat.



No, not necessarily. Pentax just didn't have time/money/or inclination to fix the problems... It was ultimately a poorly designed Samsung imager.

Yep my impression of DFS is right then, the point i was trying to make is that to do a 30 minute exposure followed by a 30 minute DFS is no different heat wise to doing a 60 minute exposure (and yes i understand its milliwatts of heat) so i would imagine (and hypothesise) if the DFS is doing a comparison, that the sensor reaches its heat output after 8 seconds and stays at a reasonably constant temp thereafter... hence the enforced DFS after 8 seconds. otherwise after a 30 min exposure the DFS running for another 30 minutes would see more heat caused artifacts..

regardless of the technicalities which im guessing we are all guessing at.. i'd still like the ability to be able to turn it off if i see fit.. so cant we just hassle pentax?

Thanks

Steve

[barondla]

if you shoot the K20D at iso 100 and keep it under 8 seconds, use the multiple exposure feature to get more total time. This will cause the random noise to cancel while stationary objects "build". Seem to remember this also working for longer exposures (DFS and multiexposure working together). Try it. Even the Canons can't do that.

Canon astrophotographers also have to pay big bucks to get focus confirmation with manual focus lenses. Then theres the EOS bugabo of using a manual lens lacking electrical contacts (think telescope), with camera teleconverter having electrical contacts. System won't fire. Unless it has changed recently theres no work around. Ouch. Grass is always greener.
thanks
barondla

Check out POINT & SHOOT CONTEST #19 WINNERS in compact camera forum. Enter #20!

---

Last edited by barondla; 06-02-2009 at 06:44 PM.

[Jodokast96]

I thought in the shots of the menu settings, you can turn it off on the K7.

[pentaxmz]

Let's face it if you want long exposures digital has a long way to go better to stick
with film. however for reletively short exposures to 40 sec's "B" mode

You're kidding right? Tongue in cheek? Right?

Few and certainly fewer pro-astrophotographers use film any more. Digital is the way to go for many reasons. One big reason is instant results, no more gas hypering (re: reciprocity failure reducer), lower magnitude gains, shorter exposures, digital stacking of shorter (sometimes hundreds) exposures, etc. etc...

Film is gone, gone, gone!! And though I have many fond memories of the yesteryears, I am very happy with what can be done with good digital imagers! That is both day time and night time photography!

Sorry and no offence intended but you couldn't be more wrong.

This mode not possible with 70's- 80's cameras as the move to electronics ment battery power, which could not keep a mirror up and shutter open for extended periods ?

Not entirely true, the amount of power required to keep a shutter open was negligible...yes, it did drain them a bit (those little button cells) but I well remember taking many hour long exposures with these cameras. Remember, in normal use, those batteries lasted, at least, a year or so. But I do remember building an external battery pack for long exposures in the winter.

[pentaxmz]

regardless of the technicalities which im guessing we are all guessing at.. i'd still like the ability to be able to turn it off if i see fit.. so cant we just hassle pentax?

Thanks

Steve

I'm willing to bet a million that it will never happen. The output would be completely unacceptable by Pentax standards. They understood this and hence, removed the option. BTW, the K20D is the only DSLR (that I know of) that doesn't allow DFS to be switched off.

Anyhow, unless someone does a hack... don't count on this happening. Like I said, you wouldn't want it anyway. Buy a K10D or wait for the K-7... or go buy a Canon.

[pentaxmz]

Seem to remember this also working for longer exposures (DFS and multiexposure working together). Try it. Even the Canons can't do that.

I'm not too sure how the Pentax K20D deals with 8 second multiple exposures.

Let's be truthful here about Canon. The 50D does allow for multiple exposures. You are correct about their previous models.

Canon astrophotographers also have to pay big bucks to get focus confirmation with manual focus lenses.

I know little to nothing about the older EOS models. But like anything Canon, there are enough owners out that that virtually all limitations have been hacked and corrected.

Then theres the EOS bugabo of using a manual lens lacking electrical contacts (think telescope), with camera teleconverter having electrical contacts. System won't fire. Unless it has changed recently theres no work around. Ouch. Grass is always greener.

It's not about 'grass is greener' is about what using what best meets your requirements. Some cameras really do have clear and obvious advantages, when working with long exposures.

What EOS model? The Canon D60 from 2002?

Your statement is a bit misleading. This is not an issue on many newer models... and where it is, there is many hacks available (ranging from firmware hacks to simple tape). Anyhow, the fact remains, for DSLRs, Canon's xxD series is preferred by astro-photographers for many good reasons.

Check out POINT & SHOOT CONTEST #19 WINNERS in compact camera forum. Enter #20!

I would, except... where do I go? I could only find the monthly photo contests.

[Jewelltrail]

mithrandir
Has anyone tried doing a 9 shot multi-exposure in lieu of a 2 minute timed exposure? Supposedly, the K10D (and I would guess K20D) exhibit less noise in multi-exposure mode.

Yes, I have used multi-exposure to reduce noise and to get an ISO 50 on the K20. Here is a link to some of the work:

https://www.pentaxforums.com/forums/pentax-dslr-discussion/56298-boosting-hig...rformance.html

[5teve]

I'm willing to bet a million that it will never happen. The output would be completely unacceptable by Pentax standards. They understood this and hence, removed the option. BTW, the K20D is the only DSLR (that I know of) that doesn't allow DFS to be switched off.

Anyhow, unless someone does a hack... don't count on this happening. Like I said, you wouldn't want it anyway. Buy a K10D or wait for the K-7... or go buy a Canon.

i was just asking if it was worth it... if i wanted a canon.. i would of bought one.. and i'd be on a canon forum asking about some issue i had found with it instead..

i bought pentax because i wanted the features pentax gives not the ones canikon give .. doesnt mean to say i cannot ask if others can be included surely?

anyways... i'll have to look at altering my methods... just dont get many storms round here to shoot at!

thanks for the idea of multi exposure..

Steve

[falconeye]

https://www.pentaxforums.com/forums/pentax-dslr-discussion/56298-boosting-hig...rformance.html

I missed this thread. So, let me make a comment here, instead:

- You haven't been aware of PhotoAcute. This software is much more capable than just stacking to remove noise. I use it on a regular base, esp. when travelling w/o a tripod. Or for long lens landcsapes.

. Stacking N images reduces effective ISO to ISO/N.

- If you stack MANY images, you start to see low spatial frequency artifacts. The K-7 seems to be much better here than K20D.

[LensScribe]

I have tried very long exposures - a few hours, on my K200D . It didn't fry the sensor. But it ran out of battery :-(
I have yet to try again with the battery grip. I don't know if the K200D it's smart enough to switch over to grip power in the middle of an exposure.

Grip on the way, so will have to try that.

I've also managed to do really long exposures on my K200D. I think the longest to date was 2.5 hours. No problems at all. Didn't melt the sensor, and didn't run out of battery (only because I made sure it was a fully charged set beforehand). Obviously, turned off the NR beforehand so that I didn't have to wait another 2.5 hours for the image to process. I frequently do >5min exposures with it (for sake of ISO 100 and F22 or similar) and haven't had any problems.

Didn't know you couldn't turn it off on K20D... which I suppose should be taken as consolation for not being able to stretch to it when I was buying, and getting the K200D instead.