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04-13-2018, 11:44 AM - 2 Likes   #1081
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K-5 at ISO 80 : Very Best APSC Sensor 4 Long Exposure

QuoteOriginally posted by gbeaton Quote
... you can get Pentax and other sensor data here: Sensorgen - digital camera sensor data
.
You've had a good idea, gbeaton !... I already know Sensorgen.info, but...
it reminds me a nice way to understand how easily the K-5 detects very faint lights at ISO 80 !
Sensorgen calculations from DxOmark Full-SNR

Open the K-5 in DxOmark Database
- Open it in a New Tab at Measurements / Full-SNR tab...
- Open the Eos 7D & Eos 1D Mk IV at Measurements / Full-SNR in 2 more Tabs
the 3 Cameras Sensor I've compared in 2011

Everything you need to know about a Camera-Sensor's Behavior in Low-Light is here

Let's Compare their Detection Threshold at -1) base ISO -2) ISO 1600
Base ISO Detection Threshold - PK-5 0,008% - C1DM4 0,036% - C7D 0,045% of Gray Scale
ISO 1600 Detection Threshold - C1DM4 0,097% - PK-5 0,109% - C7D 0,193% of Gray Scale

=> Pentax K-5 is far more Sensitive at Base ISO than a Good & Expensive Canon PRO cam.
Subtracting tens of Bias-Maps & Dark-Frames from the Eos CR2 files will lower their Noise
but they will Never Detect 0,008% Gray Details unless you Stack tens+tens of RAW files
while Pentax K-5 and its Very Low Noise only needs from 3 to 6 RAW files at ISO 80
Don't forget final results are worse than theory, Canon Banding is Not Measured :
https://en.astronomike.net/deep-sky/nebulae/162986.html

The Eos 1D Mk 4 is slightly more Sensitive than the Pentax K-5 at ISO 1600
ISO 1600 difference could be worse if shooting with Newer Canon cams

3 Re-Scaled DxOmark Full-SNR Charts Comparison posted in 2011 :
Pentax K5 vs Canon 7D : comparaisons et raisons
.
Re-Scaled DxOmark Full-SNR Charts with base ISO & ISO 1600 Detection Thresholds :
.

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Last edited by geo444; 04-18-2018 at 03:50 AM.
04-18-2018, 05:07 AM - 2 Likes   #1082
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Long Exposure @ Base ISO : a Pentax K-5 !... what else ?

.
To answer the "what else" question, I summarized :
- the Top-8 Cameras with lowest Detection-Threshold < 0,01% @ 0dB SNR, from DxOmark
same as in my previous post, ordered by Measured-ISO
- the Top-8 Cameras with lowest Noise-Levels in 5 min. Dark-Frames
from The Sensor Noise DB. Brendan Davey Photography
ordered by their Noise-Mean-Value

Pentax K-1, the 95 Top Measured-ISO with a Detection-Threshold of 0,009% @ 0dB SNR
+ the 2nd Noise-Mean-Value just behind the Pentax K-5 in 5 min. Dark-Frames (+5ev)

The very Low Dark-Current levels of the Sony imx071 explain the Pentax K-5 Top position
= the 1st lowest Noise-Mean-Value in the 5 min. Dark-Frames (+5ev) test
the Dark-Current Chart is from the Zwo Astro imaging site :
https://astronomy-imaging-camera.com/products/asi-cooled-cameras/asi071mc-pro/
Same Sony sensor, at a $1700+ price !

Then the Asi071(K-5) compared to the Asi294 and Asi1600
= two Astro-Cams with 4:3 ~22,7mm diagonal sensors

High ISO settings are mandatory to lower the Exposure Time to 1 sec. or less
this to cancel the Atmospheric Turbulence effect with long FL.
the only way to operate with Lucky Imaging !

But finally, what do you lose from Base-ISO to ISO 10K :
- Dynamic Range value from 14 ev down to 7 !
- Tone Values from 16384 down to 128 !
- SNR to be Half the Base ISO SNR
- your RAW File Size doubles
- for the same final IQ, you'll have to Stack much more RAWs...
- with Dark-Frames !
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Last edited by geo444; 04-21-2018 at 12:32 PM.
3 Days Ago - 1 Like   #1083
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Eagle Nebula and Lagoon/Trifid Nebulas with Webb's Cross

I had the IR-cut filter and anti aliasing filter removed a couple months back, and now have a capable astronomy camera with a bare sensor. I think it was about $250 conversion at spencer's camera, and is now a capable atro-photography camera.

The Eagle Nebula with the Pillars of Creation in the center I shot 90 lights and 30 darks at 45-second exposures and ISO 400 with my Skywatcher Maksutov-Newtonian 190.
The Lagoon/Trifid Nebulas with Webb's Cross in the top right corner I shot 90 lights and 30 darks at 30-sec exposures and ISO 400 with my Takahashi FSQ106ED.
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3 Days Ago   #1084
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QuoteOriginally posted by Eric Seavey Quote
I had the IR-cut filter and anti aliasing filter removed a couple months back, and now have a capable astronomy camera with a bare sensor. I think it was about $250 conversion at spencer's camera, and is now a capable atro-photography camera.

The Eagle Nebula with the Pillars of Creation in the center I shot 90 lights and 30 darks at 45-second exposures and ISO 400 with my Skywatcher Maksutov-Newtonian 190.
The Lagoon/Trifid Nebulas with Webb's Cross in the top right corner I shot 90 lights and 30 darks at 30-sec exposures and ISO 400 with my Takahashi FSQ106ED.
Congratulations Eric! They did a good job obviously

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