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05-02-2014, 11:11 AM   #1
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Quick question about K-30 read noise and ISO-lessness

I plan to go on an outing with friends to do some night sky photography (along with some other objects that will likely be light painted).

The "usual" advice for this is to fix the shutter speed such that the stars don't become trails, and then use the highest ISO available.

But I've been hearing that the K-5 is more or less an "ISO-less" camera, which means that for the same exposure time, whether you use ISO 200 and use software to increase the exposure, or shoot ISO1600, it won't make a difference - the noise in the two cases will be roughly the same. The benefit is that you won't risk blown highlights anywhere. The reason is that the "read noise" is constant across ISOs in the K-5 sensor.

Now people say the K-30 is almost, but not quite, the same as the K-5 sensor. Has anyone actually tested it in this regard? Meaning take the same shot at ISO 200, 400, 800, 1600 (same shutter speed in all cases). Will increasing the exposure in PP for 200 or 400 to the same level as the ISO1600 result in similar noise?

For most cameras that are not ISO-less, the ISO1600 photo will have less noise than an ISO 200 that is boosted in SW.

If anyone has actually checked this in the K-30, I'd really appreciate the results. I don't have time before the trip to do this experiment myself.

Thanks!

05-02-2014, 11:36 AM   #2
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I never had a K-5 but do have the K-30 and have never thought of it as being ISO-less. That being said, you can have clean shots on the K-30 up to the 3200/6400 levels that look very good especially with PP noise reduction but ISO 200 will always have less noise than ISO 1600. As for exposure levels, you are increasing a stop on each ISO increase so if you keep the same shutter speed, you will get increase in light and also increase in noise accordingly. You also need to factor in both your pictures you are taking and also if you will be shooting RAW or JPEG. RAW will have noise reduction added when you save a pic to your card and JPEG can be adjusted within the camera settings that can be set globally or on an ISO by ISO basis.
05-02-2014, 01:32 PM   #3
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http://www.sensorgen.info/PentaxK-5.html

With the dynamic range capability of the K5 you can pull up to I believe around 5 stops in post processing but still to me this method would not render as good of a quality photo then using a correct exposure triangle for the shot.

http://www.astropix.com/BGDA/SAMPLE3/SAMPLE3.HTM

Last edited by Oldbayrunner; 05-02-2014 at 02:02 PM.
05-02-2014, 02:11 PM   #4
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OK, Let's make some things clear:

1. I'm asking about RAW.
2. The exposure time and aperture are fixed.
3 This isn't about noise reduction through software.

QuoteOriginally posted by JimC1101 Quote
but ISO 200 will always have less noise than ISO 1600.
That's not true given my point 2 above. If your shutter/aperture are fixed, in most cameras, higher ISO is less noisy and desired (assuming no blown highlights). This link explains it in the simplest way:

noise - Is it better to shoot with a higher ISO, or use lower ISO and raise the exposure in post-processing? - Photography Stack Exchange

Now the issue is that with some cameras, the read noise he refers to is almost nonexistent, and K-5 is considered to be in that category. In that case, it makes almost no difference whether you shoot at ISO1600 or shoot underexposed in ISO200 and increase the brightness in software. So one might as well always shoot in ISO200 and never risk blown highlights.

My question: Has someone done the analysis with K-30?

05-02-2014, 02:29 PM   #5
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"Quick Question"
05-02-2014, 02:53 PM   #6
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QuoteOriginally posted by dadipentak Quote
"Quick Question"
Quick question. Not quick answer
05-02-2014, 03:06 PM   #7
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QuoteOriginally posted by Beetle B. Quote
OK, Let's make some things clear:

1. I'm asking about RAW.
Hmmmm....I dont see your mention of raw ...but it does have some bearing on ISO-less as with Jpeg two factors fall into consideration In camera noise reduction and loss of dynamic range whereas that is not a factor with raw

2. The exposure time and aperture are fixed.
To my knowledge of 55 years photography all exposure times and apertures are fixed for the shot.

3 This isn't about noise reduction through software.
Nor has any reply mentioned noise reduction through software only being able to lift the exposure approx imately up to 5 stops....Not the same.

My question: Has someone done the analysis with K-30?
The K5's, K30 & K50 all share the same sensor only the K30 & K50 have slighty less dynamic range

I am quite familiar with ISO-Less and Read Noise but given your response I will only advise you do further search and research into the subject.... good luck.

http://www.luminous-landscape.com/forum/index.php?topic=52178.0
http://www.luminous-landscape.com/forum/index.php?action=printpage;topic=60031.0
http://www.dpreview.com/forums/post/51792017

Last edited by Oldbayrunner; 05-02-2014 at 03:31 PM.
05-02-2014, 03:28 PM   #8
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QuoteOriginally posted by Oldbayrunner Quote
I am quite familiar with ISO-Less and Read Noise but given your response I will only advise you do further search and research into the subject.... good luck.
Oldbayrunner,

I apologize if my message seemed brash/rude - it was not my intent. I think you're confusing my post as a response to yours - it wasn't. I was responding to JimC1101. If you read his post, you can see he was confusing my intent when he said I'd get less noise from ISO 200 (which is why I explicitly restated that I'm comparing images with the same shutter and aperture).

I did not mean to imply that I had mentioned RAW. I put it explicitly in my 2nd post as a clarification because I realized I had not stated this up front. Sooner or later someone would have asked "Are we talking about RAW or JPEG?". I was merely preempting this.

He also mentioned noise reduction in PP, and I didn't want the conversation moving away from my original question, hence my comment about it. It had nothing to do with your statement about 5 stop reduction.

I could actually tell from your post you knew exactly what I was talking about from your link to sensorgen. However, it didn't tell me about the K-30.

But I was not responding to you in my last post.

For everyone, the details behind why I'm asking: I'm going to shoot the night sky with a 14mm lens, F/2.8 for about 30 seconds in an attempt to capture the Milky Way. I cannot make the exposure longer as it'll cause star trails (even 30s is pushing it). Most advice on the Internet is to shoot this at ISO1600 because on most cameras doing it at ISO 200 and increasing the brightness results in (even) more noise. However, if the K-30 is relatively ISO-less, then ISO 200 should be fine. The benefit of ISO 200 is it virtually guarantees fewer of the brighter stars will be overexposed, hence retaining their color. I can then use a curve in PP to bring out the fainter stars without impacting the brighter ones, and getting a more colorful photo. On a normal camera, this strategy is much noisier. On a K-5 it adds very little extra noise compared to shooting ISO1600. I wanted to know if the K-30 will be like the K-5 in that regard.

---------- Post added 05-02-14 at 03:31 PM ----------

QuoteOriginally posted by Oldbayrunner Quote
I am quite familiar with ISO-Less and Read Noise but given your response I will only advise you do further search and research into the subject.... good luck.

Push ISO or not? Canon vs Nikon vs Sony
Print Page - Determining if a sensor is "ISOless"
A few thoughts about ISOless (continued).: Open Talk Forum: Digital Photography Review
I appreciate the links. Sadly I won't have time to read the details prior to my trip in a few hours. I was hoping to get a quick summary if there was a clear answer. Perhaps there isn't.

05-02-2014, 05:03 PM   #9
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Unless someone is involved with the design of the camera processor (and I'm assuming that to design/program the processor they need a detailed chart of electrical characteristics of the sensor), anything they post is a guess. The K-30 has a metering range of 0 to 22 EV; 0 EV corresponds to an illuminance value of 2.5 lux or 0.23 footcandles and 22 EV is 10,496,000 lux or about 975,000 footcandles. Exposure value - Wikipedia, the free encyclopedia There is no way a photosite measuring a few micrometers can differentiate that range of light energy by itself. So the camera has to adjust the sensitivity of the sensor before it records the signal from the sensor. ISO is digital gain applied to the signal. When someone writes about "ISO-less" sensors, they should be writing that the camera is designed/programmed to negate the non-linear response of the sensor to light energy (relative to the full metering range) to the point that you can't find an ISO "sweet spot."
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