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09-23-2010, 12:15 PM   #16
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QuoteOriginally posted by Nass Quote
That's fantastic
Provided it remains as such in the production firmware release. I still think that there need to be an upgrade in the max bulb ISO limit.

09-23-2010, 12:53 PM   #17
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QuoteOriginally posted by Mehlsack Quote
As far as i know the DFS is called" noise reduktion on long exposures"(maybe wrong translation from my german menu)

I switched it off on Photokina and (as i already said) and used "Bulb" for more then 30 secs, the next picture was taken <1sec later...

So it seems that DFS in Firmware 0.1 can be switched off.
Nice! Hopefully that will be an official feature. Also, it would be nice if that feature is eventually integrated into the K-7's firmware as they have done to other firmware "downgrades" into older models in the past.

-----------------------------------------------------------

So for people who have done separate dark frames, do you just take a photo with the lens cap on? It doesn't sound like a perfect solution as some light could leak through...

Also, does it need to be the same exact amount of time, say 2 minutes for the dark frame and only 2 minutes for every picture you plan to use later?
09-23-2010, 07:46 PM   #18
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QuoteOriginally posted by KansasHorizons.com Quote
Provided it remains as such in the production firmware release. I still think that there need to be an upgrade in the max bulb ISO limit.
Long exposure at High ISO puts tremendous stress on the Sensor.
I think I'd stick to what the manufacturer feels is safe to use without damaging the sensor.
09-24-2010, 05:19 AM   #19
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QuoteOriginally posted by sjwaldron Quote
Nice! Hopefully that will be an official feature. Also, it would be nice if that feature is eventually integrated into the K-7's firmware as they have done to other firmware "downgrades" into older models in the past.
*VERY* doubtful. The issue is more the sensor than the firmware. The Samsung sensor is apparently too noisy to switch this off...I think the main issue is that the hot pixels move around (in most sensors, the hot pixels are from photosites that aren't as good as others) in the Samsung sensor...

09-30-2010, 08:42 PM   #20
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QuoteOriginally posted by kittykat46 Quote
Long exposure at High ISO puts tremendous stress on the Sensor.
I think I'd stick to what the manufacturer feels is safe to use without damaging the sensor.
I don't think you are understanding DFS.

If anything, Pentax's decision to force DFS on every exposure puts more 'stress' on the sensor because you are doubling the time of every exposure.

At any rate, the average camera sensor is a lot tougher than you imagine so I would never worry about stressing it out. When the sensor heats up, unless you are in a very hot climate, its temperature is always going to be within specifications; otherwise, it will automatically shut down.
09-30-2010, 08:55 PM - 1 Like   #21
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QuoteOriginally posted by sjwaldron Quote
Nice! Hopefully that will be an official feature. Also, it would be nice if that feature is eventually integrated into the K-7's firmware as they have done to other firmware "downgrades" into older models in the past.

-----------------------------------------------------------

So for people who have done separate dark frames, do you just take a photo with the lens cap on? It doesn't sound like a perfect solution as some light could leak through...

Also, does it need to be the same exact amount of time, say 2 minutes for the dark frame and only 2 minutes for every picture you plan to use later?
Essentially yes! And yes, you must ensure a completely DARK exposure. Don't forget that light may also leak through the viewfinder as well (a fact that many seem unaware of), so your best bet is to cover both sides.

Ideally, you want to take a dark frame at the same temperature as the original long exposure, and for the same amount of time; and with the lens cap on. However, you will only need one dark frame for every exposure time.

For example, if you took 10x 2 minute exposures, 5x 5 minute exposures, and 5x 20 minute exposures. You would need single dark frame of 2, 5, and 20 minutes. If DFS can be disabled on the Pentax K-5, that would be a savings of 1 hour and 58 minutes. What's more? You can run the dark frames when you are done your photo session!

Hopefully this illustrates how important it is to have the ability to turn off DFS!

It was so important to me, I purchased a Canon 50D just for long exposures because my K20D is useless for this type of photography.

So if it is true, the we can disable DFS on the K-5, I will buy it!
09-30-2010, 11:21 PM   #22
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QuoteOriginally posted by pentaxmz Quote
I don't think you are understanding DFS.
I don't think kittykat46 was talking about DFS, the quote was about max bulb ISO limit.
10-01-2010, 04:11 AM   #23
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I have a stupid question, but it is no trolling, really. I'm just curious.
Since digital (in general) has issues with very long exposures, why wouldn't astrophotographers use Film cameras and scan the negative ?
More steps is annoying but apart from that ?

Thank you !

10-01-2010, 04:29 AM   #24
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QuoteOriginally posted by thibs Quote
I have a stupid question, but it is no trolling, really. I'm just curious.
Since digital (in general) has issues with very long exposures, why wouldn't astrophotographers use Film cameras and scan the negative ?
More steps is annoying but apart from that ?

Thank you !
they still do for some very few type of photos (star trails was "easier" to do on film) but honestly, digital pictures are much easier to handle, to process, to make attempts see the results and correct what is needed, take several pics and stack them (to avoid trails effects), etc.. etc...

also films loose their sensibility very fast on a long exposure (reciprocity effect). Sensors dont.

dslr brought a huge step forward for astrophotograhs. Different type of technical problems can be met (noise) but all together, this is more than positive.

edit: thinking about it, only the fact you can process your own images easily makes a huge difference. How many times film labs did not developped my pics because they thought they were completely missed

Last edited by oliver939; 10-01-2010 at 04:35 AM.
10-02-2010, 09:50 AM   #25
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QuoteOriginally posted by thibs Quote
I have a stupid question, but it is no trolling, really. I'm just curious.
Since digital (in general) has issues with very long exposures, why wouldn't astrophotographers use Film cameras and scan the negative ?
More steps is annoying but apart from that ?

Thank you !
You likely have that impression because of Pentax. Astrophotographers have been regularly and successfully taking long exposures with Canon cameras since the D20).

It is all a matter of sensor design and how you mitigate the inevitable noise. Canon is light years ahead of Pentax in this regard (at least up to the K-7 - I don't enough about the K-5).

BTW, film also has 'problems' with long exposures as well. In many ways, the problems or limitations are actually much, much worst with film (the major issue is known as reciprocity failure). For this reason (and others), astrophotographers overwhelmingly prefer digital sensors. The only major issue with digital sensors is noise from dark current but this can be mitigated by cooling the sensor or taking shorter exposures and digitally stacking (combining) them - but shorter exposures have limitations too.

In general, DSLRs are not designed for long exposure photography (partly because there is no practical way to cool the sensor), at least, not in the astrophotography sense. However, Canon employs astronomy enthusiasts, at an executive level, in their organization and I believe that is why Canon goes out of their way to cater to such a small niche market.
10-02-2010, 10:28 AM   #26
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QuoteOriginally posted by pentaxmz Quote
The only major issue with digital sensors is noise from dark current but this can be mitigated by cooling the sensor or taking shorter exposures and digitally stacking (combining) them - but shorter exposures have limitations too.
Well that and amplifier glow. Since I only have my K10D because it was the last CCD sensor I have no idea where we are in the current models pursuant to this, anybody know?

Now according to Falk and others this new Sony sensor has amps on each row or column (can't remember which) will this sensor design totally eliminate amp glow?
10-02-2010, 10:42 AM   #27
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I truly hope Pentax has heard these concerns, and that DFS can truly be shut off completely. This is an extremely important issue to me personally. I have been shooting Pentax since 1985, and the K% looks very, very good to me, but I will not buy one unless I am certain that this is true.
10-02-2010, 12:02 PM   #28
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QuoteOriginally posted by pentaxmz Quote
Essentially yes! And yes, you must ensure a completely DARK exposure. Don't forget that light may also leak through the viewfinder as well (a fact that many seem unaware of), so your best bet is to cover both sides.
Thanks for the tips. What software do you use to take said dark frame and apply it to the actual photos?

QuoteOriginally posted by pentaxmz Quote
You likely have that impression because of Pentax. Astrophotographers have been regularly and successfully taking long exposures with Canon cameras since the D20)
People in the local astronomy club do a lot of stacking as apposed to long exposure stuff. I have not done anything except standard tripod photos of short exposures. I can't seem to justify the cost of a earth rotation tracking mount. :ugh:
10-02-2010, 12:18 PM   #29
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QuoteOriginally posted by sjwaldron Quote
People in the local astronomy club do a lot of stacking as apposed to long exposure stuff. I have not done anything except standard tripod photos of short exposures. I can't seem to justify the cost of a earth rotation tracking mount. :ugh:
I'm going to make up some numbers here but it applies globally. When you hear someone say that the have stacked ten 30 second shots of say Orion's belt that does not mean that they have the equivalent of a single 300 second exposure. It means they have reduced the noise of a 30 second shot by some large factor (I can't remember the formula). It is still only 30 seconds worth of photons for the signal. So your signal-to-noise ratio looks a lot better as does the final image. You still want to expose as long as you can given your equipment and local light pollution issues.
10-03-2010, 11:31 AM   #30
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QuoteOriginally posted by JackBak Quote
Well that and amplifier glow. Since I only have my K10D because it was the last CCD sensor I have no idea where we are in the current models pursuant to this, anybody know?

Now according to Falk and others this new Sony sensor has amps on each row or column (can't remember which) will this sensor design totally eliminate amp glow?
I was simplifying my post but yes, amp glow is an issue but with newer sensors it is much less of a problem with exposures under 10 minutes. The cooler the sensor, the less it is a problem and cool enough, amp glow is non-existent. Canon and Nikon have virtually eliminated amp glow on their newer sensors (I can only speak of the 50D) but my Pentax K20D is horrible for amp glow (5 min or more) and well anything over 8 seconds.

I cannot speak of the new Sony sensor on the K-5. I guess we will all just have to wait for independent long exposure reviews.
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