December 22, 2014, 08:01:35 AM

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Messages - heptagon

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31
EOS Bodies / Re: Video Review: Canon EOS 7D Mark II
« on: September 15, 2014, 01:18:16 PM »
Review? More like professional commercial spot.

32
Is this relevant for focusing speed? (E.g. Supertele+Extender @ f/8)

If no, then it's pretty irrelevant for the target audience because the sensor is too small for low light action shots.

33
EOS Bodies / Re: Canon EOS 7D Mark II Specifications Confirmed
« on: September 12, 2014, 11:12:28 AM »
This is how I shoot low light on my 30D..  I stop at ISO800..   here's the implied readout noise levels from the DxO data...  on the D800 looks like ISO200 is worth having but benefit rapidly drops beyond that.

Coincidentally the D810 now has native ISO64 because to improve DR and SNR.

For studio and landscape cameras the way to go is more Megapixels and lower ISOs.

34
EOS Bodies / Re: Canon EOS 7D Mark II Specifications Confirmed
« on: September 12, 2014, 10:06:51 AM »
If you shoot raw, then stick with ISO100 and be prepared to "underexpose" then fix in post.


well that's not good advice! :D

Care to explain why shooting at ISO100 but underexposed by 2 stops is worse than shooting at ISO400 on a Nikon 800/600 series?

Numbers are useful here.


You have two main sources of noise at low ISO:
1) Quantum noise
2) Readout noise

Quantum noise is due to the fact that photons behave like particles and if you on average expect 10000 photons in a pixel in reality you get sometimes more and sometimes less leading to a Poisson distribution around that average value. The quatum noise is the square root of the number of photons e.g. 100 for 10000 photons and 10 for 100 photons.

The readout noise is various electronic noise and depends on the amplification factor and other interference. With the new Sony sensors the readout noise is virtually the same on ISO 100 to ISO 6400 e.g. 5 electrons. With the canon sensors the readout noise is better for high ISO e.g. 3 electrons but worse at low ISO e.g. 30 electrons at ISO 100.

If you look at a bright pixel you get 10000 electrons from the photons +-100 electrons due to Poisson statistics (even a perfect sensor will get that). The S/N ratio is 100.

If you look at a dark pixel you get 100 electrons from photons and +-10 electrons from Poisson statistics. The S/N ratio is 10.

Now factor in the read noise.
- Bright pixel:
-- Canon: 100+30, S/N 77
-- Nikon: 100+5, S/N 95
- Not much difference.

- Dark pixel:
-- Canon: 10+30, S/N 2.5
-- Nikon: 10+5, S/N 6.7
- Almost a factor of 3!

If you do the same calculation at high ISO, the Canon sensor gets a little advantage.


From this we can conclude that BRIGHT pixels have the SAME QUALITY with a Canon and a Sony sensor.
But DARK pixels suffer from readout noise and here the Sony sensor is much better.

So if you do not underexpose or lift the shadows in your pictures, you will be OK with current Canon sensors.


Oh boy....


I do this stuff every day for work.

Yes poisson noise is also present, but as the two situations I'm comparing here have the same light levels, the poissn noise is identical, so we can drop it out of the equations.

Also you don't just add the noise.   it's an RMS..  (in volts) so that changes the maths a little,  Sqrt(Noise A+ Noise B)

Yes, I should have used RMS addition of the independent noise.

No, the Poisson noise is important to calculate the S/N value which considers all noise sources.


After all, this exactly explains why cameras with the same sensor size have the same SNR18% performance (in print mode) on DXO. Also it explains why the dynamic range is worse on Canon sensors compared to new Nikon/Sony sensors. Also it explains why Canon has equal or better high ISO performance.

35
EOS Bodies / Re: Canon EOS 7D Mark II Specifications Confirmed
« on: September 12, 2014, 09:35:12 AM »
If you shoot raw, then stick with ISO100 and be prepared to "underexpose" then fix in post.


well that's not good advice! :D

Care to explain why shooting at ISO100 but underexposed by 2 stops is worse than shooting at ISO400 on a Nikon 800/600 series?

Numbers are useful here.


You have two main sources of noise at low ISO:
1) Quantum noise
2) Readout noise

Quantum noise is due to the fact that photons behave like particles and if you on average expect 10000 photons in a pixel in reality you get sometimes more and sometimes less leading to a Poisson distribution around that average value. The quatum noise is the square root of the number of photons e.g. 100 for 10000 photons and 10 for 100 photons.

The readout noise is various electronic noise and depends on the amplification factor and other interference. With the new Sony sensors the readout noise is virtually the same on ISO 100 to ISO 6400 e.g. 5 electrons. With the canon sensors the readout noise is better for high ISO e.g. 3 electrons but worse at low ISO e.g. 30 electrons at ISO 100.

If you look at a bright pixel you get 10000 electrons from the photons +-100 electrons due to Poisson statistics (even a perfect sensor will get that). The S/N ratio is 100.

If you look at a dark pixel you get 100 electrons from photons and +-10 electrons from Poisson statistics. The S/N ratio is 10.

Now factor in the read noise.
- Bright pixel:
-- Canon: 100 and 30 => 104 total, S/N 96
-- Nikon: 100 and 5 => 100 total, S/N 100
- Not much difference.

- Dark pixel:
-- Canon: 10 and 30 => 32 total, S/N 3.1
-- Nikon: 10 and 5 =>11 total, S/N 9.1
- Almost a factor of 3!

If you do the same calculation at high ISO, the Canon sensor gets a little advantage.


From this we can conclude that BRIGHT pixels have the SAME QUALITY with a Canon and a Sony sensor.
But DARK pixels suffer from readout noise and here the Sony sensor is much better.

So if you do not underexpose or lift the shadows in your pictures, you will be OK with current Canon sensors.


EDIT: Use RMS for noise addition.

36
Third Party Manufacturers / Re: Zeiss Otus 85mm f/1.4 Reviews
« on: September 12, 2014, 08:00:19 AM »
DxOMark shows that this lens outresolves any of the current Canon fullframe sensors. It's been a long time since the last 1Ds...

37
EOS Bodies / Re: A Rundown of Canon at Photokina
« on: September 04, 2014, 10:36:29 AM »
4k for recording is not the same as 4k for playback.

Just compare mushy compressed 1080p with RAW 1080p. Having the option of using 4k for recording, then cropping (e.g. stabilization) and downscaling the compressed version of the video stream would be a very sensible option in many cases to produce high quality 1080p. So, no, it is not only a gimmick for people who know what they do with video.

38
EOS Bodies / Re: Plan B
« on: August 07, 2014, 07:26:13 AM »
i donĀ“t care much about aps-c.

im only interested in the 7D MK2 because i want to see what canon does and if there will be an improvement in sensor technology.

Seeing the 7D mainly as a tele/action/sports camera probably something along the lines of a good phase detection AF + improved DualPixel technology. Maybe QuadPixels. Possibly initial focus acquired by the dedicated AF sensor, then handing off to Sensor focus to follow the objects and shoot at a high frame rate without moving the mirror. This would require a hybrid viewfinder.

So for sensor technology this doesn't mean necessarily mean very much improvement in regards to quality of low ISO still images. I wouldn't expect too much in this regard.

39
EOS Bodies / Re: Plan B
« on: August 07, 2014, 06:37:16 AM »
Continue making photos with the old gear.

40
EOS Bodies / Re: 7D now marked as DISCONTINUED at Amazon
« on: July 27, 2014, 08:01:23 AM »
Actually this means that Amazon is phasing out Cannons for Nikes due to the better dynamic rage and pixels revealed with the 810D.

And I thought heptagon meant Amazon was starting to sell cold war relics in place of American Civil War relics. ;)
http://en.wikipedia.org/wiki/Project_Nike

Those Nikes you posted have quite some range. And they're big and white, too. Nice!

41
EOS Bodies / Re: 7D now marked as DISCONTINUED at Amazon
« on: July 27, 2014, 02:29:46 AM »
Actually this means that Amazon is phasing out Cannons for Nikes due to the better dynamic rage and pixels revealed with the 810D.

42
Lenses / Re: Tamron SP 150-600 f/5-6.3 VC Review
« on: January 04, 2014, 05:42:17 PM »
As the saying goes. Don't believe everything you see/hear on the internet.

So you are saying someone would just go on the internet and lie to the world?

43
Third Party Manufacturers / Re: New iPhone: Final Nail in the Coffin
« on: October 13, 2013, 09:09:33 AM »
Distance photography
...

Low-light photography
...


I'd like to add
Shallow DoF photography
What matters here is sensor size divided by f-stop number. You can only make good lenses up to about f/1 and it seems cheap lenses are stuck at around f/2. If you want to go shallower, you have to increase the sensor size.

Or to put it the other way around: A full frame DSLR with a f/5.6 lens could be replaced by a camera phone with an f/1 lens of shorter focal length and a chip of 8mm diagonal and produce THE EXACT SAME PICTURES (or even better because it has higher quantum efficiency and less read noise).

44
It seems to have some potent noise reduction algorithm.

Please take a picture of something with structure... maybe a wooden table lit by candlelight.

45
Lenses / Re: Recommend a 1.4x and 2x for my non-L lenses?
« on: September 01, 2013, 05:49:52 PM »
For which lens?

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