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Pentax K5 Long Expos in Low Light

K5: Revolutionary imx071 'Exmor' sensor inside

FPN shows mainly in Shadow areas of Canon Eos: 5d-III 6d-II 7d-II... included
Fixed Pattern Noise / EOS Shadows
Eos 5D Bias-Map Fixed Pattern Noise, FPN - Click Image, Ctrl+ to Enlarge

The way the sensor is designed lead to high Pixel Response Non Uniformity;
Power Supply corrupts sensor Analog Signal before ADC: Electronic Noise?
Even a 30sec Long Exposure at ISO 100 in Low Light is a Banding disaster:
Canon Eos DSLRs mostly Unusable at Low ISO setting in Low-Light
Lifting Shadows was very touchy in PP with almost all these Canon DSLR. In
AstroPhotography, we used to Subtract a Bias-Map (offset frame) from each
Raw file. So, it was more of a pain to deal with the Amp-Glow at bottom-right.

High Conversion Noise, Signal Corrupted fore ADC: Canon Eos (x)xD ..2019
High Convers° Noise, Signal Corrupted before ADC
FPN unseen by Dxo method is added here - Clic Image, Ctrl+ Enlarges

Pentax K5 Revolutionary imx071 Exmor, see this 5 min. ZWO Dark-Frame
imx071 Dark Frame 5min from ZWO
imx071 Dark-Frame 1000x less Noise, 0 Amp-Glow - Click Image Enlarges

The way the sensor is designed cancels 99% Pixel Response Non Uniformity
Nothing really can Corrupt sensor Digital Signal output = close to Zero Noise.
Long Exposures in Low Light at ISO 80 protecting High Lights are a pleasure
The frame is totally free of Amp-Glow even on a 300 seconds Long Exposure.
--The howto both images are from and made is written in their IPTC infos.

Exmor sensor : from Pixel to Output, ~No Conversion Noise added
No Conversion Noise from Pixel to Output
Click Image, Ctrl+ to Enlarge

Dark Current levels have been Divided by Millions since 1st 1990 CCDs Astro:
CCD ST4 of 1991 compared to Pentax K5
Pixel Response non Uniformity Levels have been Reduced a lot. Tartan Fabric,
Fixed Pattern Noise and Banding were totally absent since the Pentax K5 Sony
imx071 "Exmor" sensor. An analog Correlated double Sampling circuit before
the Analog to Digital Converter and a digital CdS after the ADC lower the PRnU
levels to never seen levels. Astro Pics from Exmor Sensor w/o any other Frame
that 3,4 Flat-Fields and only a few Sub-Frames are far better than what I got w/...

Exmor sensor ADConverter + CdS Timing Chart
Exmor ADConverter + CdS Timing Chart
Click Image, Ctrl+ to Enlarge

... my Eos 20d-5d w/ Bias-Maps, Dark-Frames, Dark+Flat-Fields, Sub-Frames:
Canon Eos-20d and Eos-5d Astro-Photography, Tests ISO-100 vs 1600
Sometimes more than 100 Frames total and the Results were just acceptable w/
Huge Amp Glow ruining each Sub-Frame. Pentax K5 is the very First CMos ILC
that totally gets rid of any Amp-Glow, even after 25 min. Exposures (I tested) !

Stacking is very efficient to Maximize the SNR of low Light Raw files that include
an imperative " Only Random Noise " Condition.

RAW Smoothing Destroys the ' Random Noise Only ' Condition by introducing
Artifacts and by Erasing many Faintest True Stars from the Raw files. Astro-Pics
Pentax Q10 w/ 4 min. exposures and w/o Raw-NR beats Sam. NX mini
require True RAWs, avoiding any Raw Smoothing or Star Eating, the Smoothing
of K5's RAW files begins at ISO-2000. Who will use the Pentax K-5 at ISO-2000
knowing that it doesn't have any Analog Amplification after ISO-80. It's far Easier
to get very Hight SNR Stacking a handful of ISO 80 Long Exposures than with 60
ISO-1k6 30sec. Expos. Am I still the only one using my K-5 at its Best ISO-80 ?

~~~~~ tbc... ~~~~~

Best APSC DSLRs (w/ 4/3, 1" stills Crop Mode)

For Astro, Birds Photography, there are not so many APSC cameras available with a
Crop Mode down to 4:3 or 1" format for stills. Now that they all get Fully Addressable
CIS, CMos Image Sensor, RoI - Region of Interest - is a totally CostLess Option, but
very useful for AstroPhotography of Deep Sky Small Objects or Birds photography !

Let's examine 2 pairs of APSC DSLRs through, a Used and a New one :

Astro Low-Light Long-Expo APSC Cams
Click Image, Ctrl+ to Enlarge

Used APSC Cameras : Pentax K-5(II(s)) betters the Eos 60d in every characteristic,
except for the Read Noise where the 60d's slightly better. Canon DSLRs were Champs
of the Conversion Noise : Eos-60d = 8.5 v PK-5 = 0.6 ! Red Layer especially suffers
from that Huge Conversion Noise level : a Stock Pentax K-5 with an UHCS filter shows
at least equivalent Red Performance than an Expensive Eos-60dA, the proofs here :
Note that the 52mm secondary mirror of my 200/1000 SkyWatcher is way too narrow !
Pentax K-5's body is Weather Sealed, its specified min.operating temperature is -10°C.
The Pentax K-5 also has a very low Dark Current level so that you can Expose until 30
minutes at ISO 80 by 12-25°C ambient Temperature and get so Clean Raw files that the
Bias Maps, Dark Frames are useless and, in most cases, you'll only need 3-8 Raw files:
17 min Exposure through an UHCS filter to darken the target, then pushed 6 Ev :
Not a bit of Banding, nor any Fixed Pattern Noise.
The Pentax K5 is IsoLess, far better results are achieved by stacking ISO 80 subs to get
a High SNR picture that you can easily Push a lot than shooting at ISO 1600 as you have
to with a Canon camera very Noisy at base ISO. 1st exceptions the last Eos R5 and R6 !

the imx071 exmor sensor inside the PK5 is so fine that chinese camera assemblers did
not hesitate launching their Asi071, Qhy168C and so on, at the high price of $3000€ = 3
times, 3x the Price I bought my Pentax K-5 New in Spring 2011 ! Some models are still
available at ~half their launch price, see how Low is their imx-071's Dark Current level:
- 1st CMos Exmor sensor, still in the Race after ~15 years on the market
QHY 168C Medium Size Cooled CMOS Camera
The very 1st sensor w/o any Amp-Glow.

Dxo 4 DSLRs APSc
Click Image, Ctrl+ to Enlarge

New APSc Camera: if I had to buy an APSc camera for Long Exposure in Low Light
or Astro-Photo today, I would certainly choose a Nikon D7500 over a Canon Eos 80d
- the Eos 90d has not yet been tested by DxoMark. Pentax K3 I, II, III are Not at the DR
level of the K5 ; they do Need Hard Raw Smoothing to follow Modern Dual-Gain BSIs.
Proof, the K3-3 Mono w/ imx571 doesn't need that Strong Raw NR to gain 2+ Ev DR.
The Eos 80d, now very close to the Pentax K5 is a high progress over the Eos 60d(a).
The Nikon D7500 beats them all in all characteristics except for Long Exposure Noise.
The Pentax K5 is still the Long Exposure King, far less Noisy than either the D7500
and the D500 which share ~very similar sensors, if not exactly the same. Canon Eos
80d is roughly in between both for long exposures, but way more noisy than both the
Nikon and the Pentax for Exposures of 30 seconds or shorter.

DxoMark 4 APSc DSLRs
Click Image, Ctrl+ to Enlarge

Now DxoMark don't allow comparing more than 3 camera. But that wasn't too difficult
for me to add the Canon Eos 60d over the screen shots of the 3 APSc DSLRs, Canon
Eos 80d, Pentax K5 and Nikon D7500, here sorted by their IQ performance rate.

~~~~~ tbc... ~~~~~

Pentax K5 v 24Mpx High End 24x36 FF DSLRs

Let's compare the Pentax K5 APSc to - 4 Full-Frame 24x36 High-End 24 Mp DSLRs :

Pentax K5 vs 24 MPx High-End 24x36 Full-Frames
Click Image, Ctrl+ to Enlarge

Incredible, the Pentax K5 beats all these Flagships in almost every criteria measured by
DxoMark ! Exception, the Nikon D3x is better of 1 bit Color-Depth in Portrait Mode,
but, was launched at $8800 in the UK - more than 8x the price I paid for my new K5 !
The better ISO score of the Full-Frames is logical, it's because their 2,33x sensor Area,
all other things being equal, the Dxo-ISO score is function of the sensor's 2 dimensions :
Low-Light Photography and Sensor Sensitivity Comparison Tools for Astronomy
You see the 24x36 are far from reaching ISO 2707 ! The Sonys are only 1,2x the K5 !
Dynamic Range: the ability to show NoiseLess Details, even in the Deepest Shadows,
and here, the Pentax K5 shines: 2,4 Ev better than the 2012 Eos 5D III, 1,8 Ev better
than the Sony Alpha-900, first camera to implement an On-Sensor ADC, an Analog to
Digital Converter which prevents aSaP the Signal to be Polluted by Conversion-Noise :
External ADC, Weak Filtering Power Supply, Weak Shielding ruin the Dynamic Range

Comments from DxoMark, plus their Review for the Pentax K-5 :
DxOMark Review, Comparisons of the Pentax K5
the Best APSC in all tested fields
~~~~~ tbc... ~~~~~
  © Dima Lootvoet 2010-2024

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