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07-08-2016, 03:26 PM   #1
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Selecting the best ISO for night/astro photography

I am moving from a Sony A7S to a K1 for a variety of reasons best discussed elsewhere.

However, one of the things that makes the move practical is the Sony sensor, which seems to provide "ISOLESS" operation based on low shot noise, etc. According to DPR, the K1 sensor is also "ISOLESS."

So, I normally leave the sony at ISO 2000, adjust my exposure settings as desired, and increase BRIGHTNESS as required in my raw images in post. For the A7S, ISO 2000 is the "sweet spot" that maximizes dynamic range while minimizing noise.

The ISO selections available on the K1 seem to be more limited, but, anyways, does anyone have any measurement data or experience that would give me a comparable ISO "sweet spot" on the K1.

Going out tonight to make some comparison test images, so any details much appreciated.

-- Rick.

07-08-2016, 03:59 PM   #2
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1600 and 3200 have been my favorite results when doing a 10-15 second exposure.
07-08-2016, 04:44 PM   #3
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I haven't shot that many star photos with the K-1 yet, but based on my experience with the D800/D810, which essentially use the same sensor, it's best to keep the ISO as low as possible and just lift the shadows. If you can get away with it, shoot at base ISO and bring a fast lens.

The photos in this thread were taken at ISO 800 F2.5, 100 F2.5, 320 F1.6, and 400 F1.6, respectively. Higher ISOs may be necessary for deep space shots, so it all depends on your objectives. But you will start seeing noise at the pixel level if you turn things up too high, and that's when tools like Topaz DeNoise can really give you an edge over the raw converter or Photoshop.
https://www.pentaxforums.com/forums/12-post-your-photos/237862-night-first-sh...cape-pics.html

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07-08-2016, 05:08 PM   #4
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QuoteOriginally posted by rcolman Quote
I am moving from a Sony A7S to a K1 for a variety of reasons best discussed elsewhere.

However, one of the things that makes the move practical is the Sony sensor, which seems to provide "ISOLESS" operation based on low shot noise, etc. According to DPR, the K1 sensor is also "ISOLESS."

So, I normally leave the sony at ISO 2000, adjust my exposure settings as desired, and increase BRIGHTNESS as required in my raw images in post. For the A7S, ISO 2000 is the "sweet spot" that maximizes dynamic range while minimizing noise.

The ISO selections available on the K1 seem to be more limited, but, anyways, does anyone have any measurement data or experience that would give me a comparable ISO "sweet spot" on the K1.

Going out tonight to make some comparison test images, so any details much appreciated.

-- Rick.
I use ISO 1600 on my K-5. Sometimes ISO 3200, but post processing is an important part which is a bit lacking (in terms of dynamic range) at that ISO.

I think ISO 1600 would be very fine in the K-1, especially with the 36 MP "ISOLESS" sensor.

Also, may I ask why you're moving away from the A7S? I've been considering that camera for its low-light performance.

07-08-2016, 07:20 PM   #5
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QuoteOriginally posted by rcolman Quote
The ISO selections available on the K1 seem to be more limited
Pentax bodies have a setting for either half-stop or third-stop exposure increments. It seems to default to half-stops. Change it to third-stops and you get more ISO options.
07-08-2016, 07:30 PM   #6
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Moving from Sony to Pentax

Well, not sure I am moving yet. I will try some comparison shots tonight, I hope.

There is nothing wrong with the A7S, per se. It is my particular circumstances. I specialize in a certain kind of night photography where I MUST-MUST-MUST have built-in GPS, preferably with compass, and have that data punched into the image EXIF. Sony did not provide it, promised they would, have not so far, and may never do it. The market is too small for third-party providers. If you look at some of my recent stuff, you can tell that location is important:

Ritual Landscapes at Night - WesternRockArt

most of which were taken with the A7S and various manual lenses.

Also, I tell you, the ergonomics are not that good. The buttons and controls are poorly placed, and impossible to find in the dark, yada yada yada

The K-1 solves a lot of these problems for me, hopefully the image quality is there. I need really low noise, and, with the A7S I can shoot anywhere from 2000 to 51,000 ISO and the noise levels are about the same.

But, the damn thing is so small, it can be hard to handle, particularly because the FF lenses are about the same size anywhere. On the otherhand, when I pick up the K-1 it seems to weigh about 100 lbs.

We will see.
07-08-2016, 08:52 PM - 1 Like   #7
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For some very interesting ISO and long-exposure sensor noise data for many digital cameras, this is a very revealing site:

The Sensor Noise DB. – Brendan Davey Photography

In short, K-1 (and K-5) offer lower levels of long exposure sensor noise than just about anyone else.



It's also quite surprising how some cameras that rate well for high ISO eg on dxomark.com - like the Nikon D610 and Sony A7S - perform very poorly for long exposures.

Last edited by rawr; 07-08-2016 at 08:57 PM.
07-08-2016, 09:53 PM   #8
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QuoteOriginally posted by rcolman Quote
I am moving from a Sony A7S to a K1 for a variety of reasons best discussed elsewhere.

However, one of the things that makes the move practical is the Sony sensor, which seems to provide "ISOLESS" operation based on low shot noise, etc. According to DPR, the K1 sensor is also "ISOLESS."

So, I normally leave the sony at ISO 2000, adjust my exposure settings as desired, and increase BRIGHTNESS as required in my raw images in post. For the A7S, ISO 2000 is the "sweet spot" that maximizes dynamic range while minimizing noise.

The ISO selections available on the K1 seem to be more limited, but, anyways, does anyone have any measurement data or experience that would give me a comparable ISO "sweet spot" on the K1.

Going out tonight to make some comparison test images, so any details much appreciated.

-- Rick.
I‘not sure whether you will use astrotracer. If yes, then K1 seems to perform really well.
I tested the performance of my new K1 using ISO 800 with astrotracer on and the results have been really well. See the photos below:








Extra images can be found at: https://www.flickr.com/photos/135475528@N04/
I also tested the noise of K1 at different ISO and you may be interested to check this thread: https://www.pentaxforums.com/forums/190-pentax-k-1/324494-pentax-k1-test-nois...erent-iso.html

07-08-2016, 10:43 PM   #9
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Similar to ds7711, I use lower ISO settings 400-800 for any astrotracer shots I take. If I'm not using the astrotracer, then I'll default to either 1600 or 3200 with a 15s+ shutter time at f/2.8 (I use a samyang 10mm, f/2.8 is the widest aperture setting on that lens). But getting back to the astrotracer, I'll normally default to ISO 640, f/3.5, 150s shutter time as my preferred settings for milky way shots. I use a K-3II, so the K-1 should have a several stop advantage for low light.
07-13-2016, 12:48 AM - 1 Like   #10
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Does anyone know if this is correct??

The sensor in the Pentax K-1 is the same one found in the well-regarded Sony a7R, with great dynamic range and color accuracy.

????
07-13-2016, 05:15 AM   #11
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QuoteOriginally posted by rawr Quote

In short, K-1 (and K-5) offer lower levels of long exposure sensor noise than just about anyone else.

It's also quite surprising how some cameras that rate well for high ISO eg on dxomark.com - like the Nikon D610 and Sony A7S - perform very poorly for long exposures.
Those are 300 x 300 pixel crops, which means that cameras with lower pixel density are shown at lower magnification, giving them an unrealistic advantage.
07-13-2016, 02:41 PM   #12
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QuoteOriginally posted by rcolman Quote
Does anyone know if this is correct??
The sensor in the Pentax K-1 is the same one found in the well-regarded Sony a7R
And the D800. And the D810.
With some minor tweaks from each camera maker.

QuoteOriginally posted by audiobomber Quote
Those are 300 x 300 pixel crops, which means that cameras with lower pixel density are shown at lower magnification, giving them an unrealistic advantage.
Perhaps. He himself notes:

QuoteQuote:
A few points to keep in mind when reviewing the results:
- The age of the camera.
- If the camera supports fully disabling NR (some do not, and in some models it can affect the RAW file).
- Additional processing applied to the image regardless of the NR settings.
- The size and pixel density of the sensor.
But the full sensor comparisons he provides do remove the apparent advantage of the smaller sensor/big pixel crops.

If you remove concerns about pixel density and sensor size, by comparing 24MP vs 24MP FF, or 36MP vs 36MP FF (ie same sensor size, same pixel density) you will still see some interesting variation happening, even between relatively similar modern sensors (eg A7 vs A7II vs D610 vs D750, A7R vs D810 vs K-1). So I think his results may be showing something useful, if long-exposures are important to you.
07-13-2016, 05:51 PM   #13
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QuoteOriginally posted by rawr Quote
If you remove concerns about pixel density and sensor size, by comparing 24MP vs 24MP FF, or 36MP vs 36MP FF (ie same sensor size, same pixel density) you will still see some interesting variation happening, even between relatively similar modern sensors (eg A7 vs A7II vs D610 vs D750, A7R vs D810 vs K-1). So I think his results may be showing something useful, if long-exposures are important to you.
I agree with the above, but the 300x300 pixel crops are pointless and misleading, and should be dropped from the comparisons.
07-19-2016, 01:43 PM   #14
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QuoteOriginally posted by rcolman Quote
Does anyone know if this is correct??

The sensor in the Pentax K-1 is the same one found in the well-regarded Sony a7R, with great dynamic range and color accuracy.

????
I don't believe it's the same exact sensor as the K1 has electronic first curtain (only used in Pixel shift currently), Sony had plenty of issues with vibration due to 1st curtain on the A7r and changed this on the A7rII. More than likely the K1 is using the same Sony sensor that is in the Nikon D810.

Paul C
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