Long write times (?) with K-70 in astrophotography mode.

patrickmb · 05-26-2020, 09:44 PM

Hello everyone,

I recently bought and started using a K-70 and love using the astrophotography function. However, after long exposures I often will have to wait longer than the exposure itself for the camera to be useable again. The orange light is flashing during this down time which I believe to mean the data is writing to the SD card. Is this normal? Is there anyway to reduce this time?

Thanks for your help!

**jatrax** · 05-26-2020, 09:59 PM - **1 Like**

On long exposures the camera will do a dark frame exposure after the first exposure. I'm not familiar with the K-70 so I cannot say if that is fixed or optional.

Here is some additional information: Bulb time setting on K-70 - PentaxForums.com

kypfer · 05-26-2020, 11:29 PM - **1 Like**

Originally posted by patrickmb

Hello everyone,

I recently bought and started using a K-70 and love using the astrophotography function. However, after long exposures I often will have to wait longer than the exposure itself for the camera to be useable again. The orange light is flashing during this down time which I believe to mean the data is writing to the SD card. Is this normal? Is there anyway to reduce this time?

Thanks for your help!

The long "write time" is actually the camera doing it's high ISO or long shutter time noise reduction. Both features can be disabled, but at the expense of noisier images. It is possible to take separate "dark frames" then combine everything in software later ... the same set of dark frames can be used over and over again, so once having taken them once, you'll not need any more that session provided the other parameters such as focal length and exposure time remain the same.

For reference, my brief tests indicate an exposure of 30sec with 400 ISO to be as long as the camera will go before invoking noise reduction. With a wide-aperture lens this is often more than enough in an area where sky-glow is a problem

Good luck

shyrsio · 05-27-2020, 04:01 AM

Same thing happens on my K1 on astrophoto

**MossyRocks** · 05-27-2020, 09:10 AM - **1 Like**

Turn of long exposure (slow shutter speed) noise reduction. Basically the camera is taking a dark frame for each light frame it takes and subtracting that dark frame from the light frame. While this improves results some if you are serious about doing astro take your own dark frames at the end and take a bunch of them (20-30 is usually good). Almost all astro stacking programs will accept these dark frames and create a master dark frame. This master dark frame will have substantially lower random noise so will better show the systematic error which then can be subtracted from each of the light frames. This provides a better result than what is done by the camera when it does it one at a time. This is because there is a lot of random noise in a single dark frame so subtracting that one dark from one light will improve things the random noise is still fairly strong so the result isn't as great as subtracting an averaged master dark made from many dark frames. I think one can even use master darks in RawTherapee but I haven't played around with that feature.

Light frames - This provide a stronger signal and when combined will drive down random noise and some systematic errors if you are dithering images
Dark frames - These are used to remove systematic sensor errors. Hot pixels, dark current, sensor hot spots. If given a choice I will always take more light frames over dark frames and only collect these when tearing down and packing up. These are session dependent as the environment will affect them.
Bias frames - These are used to remove systematic errors in the read, signal amp, and AtoD converter (on modern cameras you need lots of these like over 100 because these errors are really low now). These are the least important but the good news is that they are easy to capture and can be captured any time.
Flat frames - These are used to remove vignetting and also dead or slow pixels. These are the second most important frames if you are doing astropyhotography and can be captured any time.

nite-sky · 03-10-2021, 08:34 AM

Originally posted by patrickmb

Hello everyone,

I recently bought and started using a K-70 and love using the astrophotography function. However, after long exposures I often will have to wait longer than the exposure itself for the camera to be useable again. The orange light is flashing during this down time which I believe to mean the data is writing to the SD card. Is this normal? Is there anyway to reduce this time?

Thanks for your help!

What is the "write" speed of your SD card? If it has a slow write speed then processing the photo will take a considerable amount of time. I would suggest a web search of the different capabilities of SD cards and pick one you're comfortable with. Something over 200 MB/s will really help.

05-26-2020, 09:44 PM	#1
patrickmb New Member Join Date: May 2020 Posts: 1	Long write times (?) with K-70 in astrophotography mode. Hello everyone, I recently bought and started using a K-70 and love using the astrophotography function. However, after long exposures I often will have to wait longer than the exposure itself for the camera to be useable again. The orange light is flashing during this down time which I believe to mean the data is writing to the SD card. Is this normal? Is there anyway to reduce this time? Thanks for your help!

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Black & White Good Times, Bad Times	Bob Harris	Post Your Photos!	7	06-22-2014 01:21 PM
k5 slow write times	malibru	Troubleshooting and Beginner Help	6	09-21-2013 09:59 PM
Mushkin 32gb Class 10 mknsdhcc10-32gb Slow write times	davidreilly3207	Troubleshooting and Beginner Help	2	04-27-2012 03:49 AM
Slow Pentax K-7 buffer and write times	btwalters	Pentax DSLR Discussion	6	12-27-2010 08:34 AM
Time Exposure - Bulb setting - Read write times	Vatis	Pentax DSLR Discussion	7	09-05-2007 07:38 AM

05-26-2020, 09:59 PM - 1 Like	#2
jatrax Site Supporter Join Date: May 2010 Location: Washington Cascades Photos: Gallery \| Albums Posts: 12,992	On long exposures the camera will do a dark frame exposure after the first exposure. I'm not familiar with the K-70 so I cannot say if that is fixed or optional. Here is some additional information: Bulb time setting on K-70 - PentaxForums.com

05-26-2020, 11:29 PM - 1 Like	#3
kypfer Pentaxian Join Date: Jan 2018 Location: Jersey C.I. Posts: 3,600	Originally posted by patrickmb Hello everyone, I recently bought and started using a K-70 and love using the astrophotography function. However, after long exposures I often will have to wait longer than the exposure itself for the camera to be useable again. The orange light is flashing during this down time which I believe to mean the data is writing to the SD card. Is this normal? Is there anyway to reduce this time? Thanks for your help! The long "write time" is actually the camera doing it's high ISO or long shutter time noise reduction. Both features can be disabled, but at the expense of noisier images. It is possible to take separate "dark frames" then combine everything in software later ... the same set of dark frames can be used over and over again, so once having taken them once, you'll not need any more that session provided the other parameters such as focal length and exposure time remain the same. For reference, my brief tests indicate an exposure of 30sec with 400 ISO to be as long as the camera will go before invoking noise reduction. With a wide-aperture lens this is often more than enough in an area where sky-glow is a problem Good luck

05-27-2020, 04:01 AM	#4
shyrsio Pentaxian Join Date: Apr 2016 Location: Tirana Posts: 780	Same thing happens on my K1 on astrophoto

05-27-2020, 09:10 AM - 1 Like	#5
MossyRocks Loyal Site Supporter Join Date: Nov 2017 Location: Minnesota Photos: Gallery \| Albums Posts: 2,982	Turn of long exposure (slow shutter speed) noise reduction. Basically the camera is taking a dark frame for each light frame it takes and subtracting that dark frame from the light frame. While this improves results some if you are serious about doing astro take your own dark frames at the end and take a bunch of them (20-30 is usually good). Almost all astro stacking programs will accept these dark frames and create a master dark frame. This master dark frame will have substantially lower random noise so will better show the systematic error which then can be subtracted from each of the light frames. This provides a better result than what is done by the camera when it does it one at a time. This is because there is a lot of random noise in a single dark frame so subtracting that one dark from one light will improve things the random noise is still fairly strong so the result isn't as great as subtracting an averaged master dark made from many dark frames. I think one can even use master darks in RawTherapee but I haven't played around with that feature. Light frames - This provide a stronger signal and when combined will drive down random noise and some systematic errors if you are dithering images Dark frames - These are used to remove systematic sensor errors. Hot pixels, dark current, sensor hot spots. If given a choice I will always take more light frames over dark frames and only collect these when tearing down and packing up. These are session dependent as the environment will affect them. Bias frames - These are used to remove systematic errors in the read, signal amp, and AtoD converter (on modern cameras you need lots of these like over 100 because these errors are really low now). These are the least important but the good news is that they are easy to capture and can be captured any time. Flat frames - These are used to remove vignetting and also dead or slow pixels. These are the second most important frames if you are doing astropyhotography and can be captured any time.

03-10-2021, 08:34 AM	#6
nite-sky New Member Join Date: Oct 2020 Posts: 5	Originally posted by patrickmb Hello everyone, I recently bought and started using a K-70 and love using the astrophotography function. However, after long exposures I often will have to wait longer than the exposure itself for the camera to be useable again. The orange light is flashing during this down time which I believe to mean the data is writing to the SD card. Is this normal? Is there anyway to reduce this time? Thanks for your help! What is the "write" speed of your SD card? If it has a slow write speed then processing the photo will take a considerable amount of time. I would suggest a web search of the different capabilities of SD cards and pick one you're comfortable with. Something over 200 MB/s will really help.