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01-19-2012, 11:11 PM   #1
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Card reading

Does anyone have any answers to the long agonizing length of time it take to write onto the SD card? For lightning or long exposures the reading takes as long as the exposure which means I often miss on the next few shots. I have spoken to the Pentax people here and all I get is the Pentax cameras read the 'black' whatever that means. All I know is several of us were shooting lightning the other night and while all the blasted cannon folk were getting instant feedback, and exposing the next shot, I was still waiting for mine to read. I have gone off RAW and just on JPG in case that speeds things up but it does not. I am using Sandisk 8gb Extreme Pro. If this can't be solved I might have to buy a little second hand cannon just for slow mo, and lightning. I did a four minute moonlight shot last week and it took just that: four minutes to read!

01-19-2012, 11:18 PM   #2
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It isn't about "writing to the card". It is the noise reduction routines. Turn off all in-camera noise reduction and there will be no delay, but I think some models actually don't let you turn it off for long exposures. But that's the reason. What it is doing is taking an exposure of "black" -- shutter closed but with other camera settings the same as your shot -- including shutter speed which is why it takes exactly as long as your shot did. This is supposed to create a noise pattern the same as on your shot which is then mathematically "subtracted" -- that's how in-camera NR works. You can actually do the same thing yourself in Photoshop if take a "black" picture with the same settings.
01-19-2012, 11:26 PM   #3
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+1
Switch off all in-camera psot-processing incl. NR, lens distortion correction, ... In fact the pictures are first stored in the camera buffer before being stored/written on the card.
01-19-2012, 11:45 PM   #4
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Oops. can you slow all that down a little. I have the K7 which I should have mentioned. I am not sure about all these in-camera settings you are telling me about. So, could you pretend I am quite stupid. (Hmmm) Where is 'in camera noise reduction' and lens distortion correction. Love that you are trying to help me.

01-20-2012, 12:15 AM   #5
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QuoteOriginally posted by vonBaloney Quote
You can actually do the same thing yourself in Photoshop if take a "black" picture with the same settings.
Unsure of meaning of this one.

Think I am nearly there. Have found noise reduction and turned it off, plus slow shutter speed noise reduction. My lens correction thingy is in grey and does nothing. Do I just do this for slow shots or leave them off all together. Plus what ISO do you think best for lightning. One I did get is very 'noisy" Will post it tomorrow as now have to go to work. Thanks will look forward to replies.
01-20-2012, 02:20 AM   #6
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QuoteOriginally posted by trishytee Quote
Oops. can you slow all that down a little. I have the K7 which I should have mentioned. I am not sure about all these in-camera settings you are telling me about. So, could you pretend I am quite stupid. (Hmmm) Where is 'in camera noise reduction' and lens distortion correction. Love that you are trying to help me.
I have also a K-7. Go to camera settings. (I assume that you read the instructions and you can go to the camera settings.) Switch off Lens distortion correction, High ISO Noise Reduction and any other function which woudl require the camera CPU to process the photograph immediately after the shot was taken (and before the file is written to the card.)

Last edited by hcc; 01-20-2012 at 03:04 AM.
01-20-2012, 06:39 AM   #7
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What the speed of your SD card. I use Class 10's and would like the new 90ms SD cards, but the are too expencive at the moment. If you shoot in JPEG the turning of High ISO NR will help.
01-20-2012, 08:30 AM   #8
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The problem is the NR -- NR doubles the amount of time to take any shot, so just turn it off. (I think other brands do the same thing for long exposure in-camera NR -- it isn't just a Pentax thing.) Now then, your long-exposure shots will now be very noisy because you turned off the NR and long shutters create noise on digital sensors. So any noise-reduction will have to be done in post-processing. That's a whole other subject.

My mention of photoshop was just an aside to point out that you can actually apply "in-camera" noise reduction later in photoshop using the same method (more or less) as what the camera is doing -- but you still have to take that "black" shot. Any other noise reduction method has to decide (i.e. guess) what is noise and what isn't whereas the in-camera version just creates an equivalent noise pattern -- that's the theory anyway, but some noise is always just random -- your sensor will be hotter or whatever. Anyway, it takes this noise pattern and uses it subtract noise from the original image. (Noise reduction of any method should always be the *first* thing you do to an image if you're going to do it.) So the only way to mimic in-camera noise reduction is to have that equivalent noise pattern to work with. It is too much trouble to do when constantly changing camera settings, but let's say you are going to take a bunch of long exposures all for exactly the same shutter speed (EXACTLY), same iso. Now you could leave the lens cap on for ONE shot to create your own black noise pattern and use for noise reduction in Photoshop later. (Which involves making an alpha channel of the black and blah blah blah -- something else to learn about.) In practice no one actually does this (anymore) because the NR routines in Lightroom and other programs are very good. (Is the one in the Pentax utility any good?)

Bottom-line, long exposures are noisy, and you'll probably want to deal with it one way or another. So that means either waiting double-time for each shot or post-processing. Note that all third-party NR programs (Lightroom, Noise Ninja, etc) all advise turning off ALL in-camera NR off so their programs will have an easier time determining what is noise, and applying their NR first-thing (before adjusting ANYTHING else -- exposure, etc).


Last edited by vonBaloney; 01-20-2012 at 10:21 AM.
01-20-2012, 09:12 AM   #9
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QuoteOriginally posted by trishytee Quote
Unsure of meaning of this one.

Think I am nearly there. Have found noise reduction and turned it off, plus slow shutter speed noise reduction. My lens correction thingy is in grey and does nothing. Do I just do this for slow shots or leave them off all together. Plus what ISO o you think best for lightning. One I did get is very 'noisy" Will post it tomorrow as now have to go to work. Thanks will look forward to replies.
The K7 uses dark frame subtraction (DFS) and you can't turn it off i believe.
It works by making a black photo after the exposure and it uses the same settings for that, so if you use ISO200 30 seconds, then it takes another photo also at ISO200 and 30 seconds but with the shutters up.
So it gets a black photo but it shows the "fix" noise the sensor makes.

You can hack your way into it and turn it off with a script and if you've debug menu enabled.

turn off DFS with your K20D and K7


DFS is only turned on with long exposers
01-20-2012, 01:22 PM   #10
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QuoteOriginally posted by trishytee Quote
Think I am nearly there. Have found noise reduction and turned it off, plus slow shutter speed noise reduction. My lens correction thingy is in grey and does nothing. Do I just do this for slow shots or leave them off all together. Plus what ISO do you think best for lightning. One I did get is very 'noisy" Will post it tomorrow as now have to go to work. Thanks will look forward to replies.
Well, you did just turn off noise reduction, so no surprise the result is noisy. That feature is there for a reason.

But as for what ISO to shoot, that depends on what aperture you wish to shoot at and what shutter speed you wish. If you don't mind 30-second or longer exposures at a large aperture, you can use lower ISO. If you wanted faster shutter speeds or a smaller aperture, you'll need ISO. That's for you to decide. Shooting lightning is subject to the exact same basic tenets of exposure as shooting any other type of scene.
01-20-2012, 01:45 PM   #11
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You could get a lightning trigger to keep exposures short if you're not going for those shots that combine multiple strikes over time.
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