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11-04-2010, 09:21 AM   #1
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Time exposures with a K-7

Hi, I'm new to the forum. I have been using film cameras for many years and am seriously thinking about changing to digital. I cut my teeth with a Practica LTL and then moved on to a K1000, which is a fabulous camera. I also use a Mamiya RB67 and my main passion is photographing trains. I've always had great success with night photography using time exposures. My preferred method has always been low ISO, stopped down lens and long exposure on daylight slide film.
The camera that most takes my fancy at the moment is the K-7. My question is, can I take long exposures, I'm talking several minutes, and how will it cope with these long exposures?
I've attached a couple of examples, the top one was 6 mins @F16, the second one was 90 seconds @F11.
Any help will be greatly appreciated.

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11-04-2010, 10:02 AM   #2
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While I don't own a K7, I do own a k10 & k20 and I believe this to be an accurate statement. I think you will find that the K7 (and a lot of other DSLRs), have a maximum time setting of 30 seconds. However, as the K7 (and others) have a bulb setting you can use this for much longer time exposures (I've done exposures of 3 to 6 minutes at times). You will need either a remote shutter release which is the best because you can lock it just like a cable release on a film camera or a wireless trigger - not as good because you have to hold it on to keep the shutter open. There are other things to consider too on time exposure such as turning off noise reduction and buffer recovery times but that's another topic. Bottom line answer is yes you can do this.

Nice train photos!
11-04-2010, 10:09 AM   #3
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10 seconds at f8 ISO 100



20 seconds at f8 ISO 100

[IMGTALL]http://farm5.static.flickr.com/4017/4386942158_a4503d2c68_o.jpg[/IMGTALL]


20 seconds at f8 ISO 100




Lens is the DA15mm Limited.

Put your train in any one of them and you be the judge (I like taking pictures of trains too but mine or scaled down a bit )

50 seconds f2.8 ISO 100 Penatax A 50mm f1:1,2



30 Seconds f4.5 ISO 100, Same lens



103 Seconds f2.8 ISO 100, Same lens




Last edited by JeffJS; 11-04-2010 at 10:15 AM.
11-04-2010, 10:19 AM   #4
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QuoteQuote:
You will need either a remote shutter release which is the best because you can lock it just like a cable release on a film camera or a wireless trigger - not as good because you have to hold it on to keep the shutter open.
I know thats true with my K100D but I thought on some models there was a setting that allowed for "one-click shutter up, second-click shutter down"?

11-04-2010, 10:40 AM   #5
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QuoteOriginally posted by Capslock118 Quote
I know thats true with my K100D but I thought on some models there was a setting that allowed for "one-click shutter up, second-click shutter down"?
There is and it exists on the K7 but I've never tried it. I think it will work with a wireless remote though. I've never tried it because I always figured the close shutter click would shake the camera. For me, it's simpler to use a $5 locking wired remote cable.

11-04-2010, 12:03 PM   #6
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Welcome velvia.
As mentioned it is possible with the K-7 though in my opinion the best results for exposures longer than 30secs would come from the K-5 or the old K10D. Whilst I have no experience with the K-5 there is evidence on this forum that it performs very well with long exposures. Between my K20D (which is very similar to the K-7 in results) and my K10D, long exposures come out significantly noisier on the K20D and quite smooth on the K10D. This holds for all ISOs (100-400). Nevertheless it can be done and provided you're not after very long exposures ( >5mins) you should get excellent results from the K-x.
11-04-2010, 04:57 PM   #7
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QuoteOriginally posted by JeffJS Quote
There is and it exists on the K7 but I've never tried it. I think it will work with a wireless remote though. I've never tried it because I always figured the close shutter click would shake the camera. For me, it's simpler to use a $5 locking wired remote cable.

Yes, on the K-7 it works with the wireless remote. One press to open shutter, second one to close. Or in the mirror lock-up mode - one press to focus and lock up, second to open shutter, third to close and finish. A cheap remote - I've got something called 'uWinKa' off eBay - costs less than a locking wire release cable
11-04-2010, 05:21 PM   #8
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I've had good results with my K-7 for up to 10 minutes in cooler weather (read Canada wintertime), the main issue is that a second frame will be "shot" to determine and remove "hot" (or malfunctioning) pixels. The upshot is that a 10 minute exposure becomes 20minutes. this process (which kicks in after 29 seconds exposure time on the K-7) does make images a bit softer.

Another option if you are working off a tripod (which I assume you are, given 7min exposures), and if your subjects aren't moving, is to exposure stack several shorter exposures, and use photoshop to combine the images and remove the noise. This is common for astrophotography, and works quite well.

I bought a timer remote, which has the added benefit of allowing you to go inside and have a wine and let your camera do it's thing outside, at 2am in the morning or whatever. Also good for timelapses.

The one click open and one click close shutter is very useful if you don't have a release with you. I've used it for night shots If I am travelling with only a couple of primes and an ultrapod while camping, and it has been very useful.


Last edited by Clarkey; 11-04-2010 at 05:21 PM. Reason: spelling
11-05-2010, 07:38 AM   #9
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Dark Frame Subtraction

One often-heard complaint about the K-7 and long exposures is that there is no option to disable dark-frame-subtraction. Since the OP says he is new to digital photography, perhaps a bit of explanation is in order.

With any digital camera, the sensor is, of course, electronic. In any electronic device, there is a phenomenon called "noise". This is like static on a radio. It is unwanted electrical signals. In a digital camera, this noise degrades the image, and appears a little like grain in film. It is most prevalent in dark areas of an image and at higher ISO settings. It also shows up more in long exposures.

Dark frame subtraction is a technique that many camera makers use to try to minimize the effect of noise. First you take a picture at, say, 60 seconds. The camera then takes another picture of equal length, but this time, with the shutter closed. The idea is that any pixels that are illuminated in the second image are, by definition, noise. This second image is then used to "subtract" the noise from the first image, theoretically resulting in a better image.

Many users are confused and frustrated by this. It can be annoying, if you're taking very long exposures of several minutes. The camera is not ready to take anouther picture for a length of time equal to the exposure you just did. So, if you take a five minute exposure, the camera is not ready to take another picture for five full minutes after the exposure is complete.

Some Pentax cameras allow you to turn this feature off. The K10D allowed this, but I don't think that any newer Pentax cameras do. I'm almost positive that the K-7 does not, but I've heard that perhaps the brand-new K-5 does allow it to be turned off.
11-05-2010, 07:58 AM   #10
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Many thanks to all posters. I think after, reading them, that I will wait until reviews on the K-5 appear and see which looks like the better option. Hopefully the price will have come down a bit in the meantime.

David Franklin.

Last edited by velvia; 11-05-2010 at 07:59 AM. Reason: Memory loss.
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