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07-07-2014, 07:37 AM   #91
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Sure.

But just for reference, the improvement in low light from the D700 (pretty awesome for the time) to the D800 was about the improvement we're talking about from the A7R to the A7S. Great improvement! ... and I'll take it for low light (I won't take the A7S overall, because I'm usually at low-ISO, where the A7R is better). But it's not a game-changer in my view.

---------- Post added 07-07-14 at 07:38 AM ----------

QuoteOriginally posted by nater Quote
Right, I just care about the Sony cameras because it helps me see what sensors might be down the road for Pentax. The K-5 has a Sony sensor, the K-3 has a Sony sensor, the 645Z has a Sony sensor (no more Kodak sensor like the 645D!) Nikon uses Sony sensors. I figure Sony is taking the best sensors for themselves first, and other makers will get them eventually. I already have a 28-70mm f/2.8 and 70-200mm f/2.8 for my Pentax, and they got a terrific upgrade going from my K200D to the K-5. I'm looking forward to another upgrade with a future Pentax body (that will likely have a Sony sensor).
It's odd that the A7S had it's 'first implementation' on the full-frame body. Usually improvements in sensors start paradoxically at the smaller-sensored-cameras. Perhaps Sony's wafer yield was such that it didn't need that intermediate step.


PS - I went from the K200D to the K-5, too. Phenomenal improvement, a bit over one stop!

07-07-2014, 07:43 AM   #92
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QuoteOriginally posted by ElJamoquio Quote
Stops are the grid markers on the horizontal line. You see that at any given dB, the horizontal distance between the K-7 and the K-5 is about a stop.
Where are you getting this from? Everything I read says 3dB = 1 f-stop. For instance:

The paradoxical evolution of sensor SNR over time - DxOMark

"To understand the SNR scale, remember that a 3dB difference between two cameras is roughly equivalent to a difference of one f-stop. That is, if camera A at ISO200 has an SNR of 3dB or larger than that of camera B, then camera A at ISO400 will have approximately the same SNR as camera B at ISO200, meaning that camera A will out-perform camera B by one stop."

QuoteOriginally posted by ElJamoquio Quote
Again, I never compared the A7S to the K5. We were talking about improvements, i.e., 'game-changers'. The K7 to K5 improvement was twice the game changer of the A7R to the A7S.
Ah, I only care about comparing the A7S to the K-5/K-3, because I care about future Sony sensors used in Pentax bodies. Sony bodies don't matter to me otherwise, it's not like I'm going to go out and buy a Sony! And if Pentax came and asked me if I'd like them to come out with a FA * 85mm f/1.4 SDM WR and FA * 135mm f/1.8 SDM WR or a body with the sensor from the A7S, I'd say body with the sensor from the A7S, hands down.
07-07-2014, 07:57 AM   #93
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QuoteOriginally posted by nater Quote
Where are you getting this from? Everything I read says 3dB = 1 f-stop. For instance:
I'm reading the graph. The horizontal axis grid markers are one stop. Look up the A7S at a given fidelity - for example 30 dB. I think you'll find that the ISO value is 3702. Do the same for the A7R, and I think you'll find that fidelity at 2746.

3702/2746 = 1.348, or about a third of a stop.

(I chose 30 dB because I think that's how DxO evaluates it's high-ISO capability of a camera, and it also seems, to me, to be a reasonable limit for a 8x12 print).

The slope you've quoted - 3dB / f-stop - is just an approximation based on lots of cameras. It might've been more true a few years back. Right now the A7S has 45.1 dB at ISO 80 and 39.9 at ISO 329. Let's call that two stops, and 5.2 dB of difference. You might call that close enough but that's decibels are a logarithmic scale, so it's quite a difference.
07-07-2014, 11:01 AM   #94
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QuoteOriginally posted by ElJamoquio Quote

The slope you've quoted - 3dB / f-stop - is just an approximation based on lots of cameras. It might've
3dB is also quite formally the result of doubling or halving power.

07-07-2014, 11:46 AM   #95
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I think the big thing about the A7s is that it doesn't actually perform much better than existing sensors until you get really high iso (more than 25,000), at which point it does seem to gain quite a bit over existing full frame Nikon options like the D800e or D4. It isn't great at those isos, but it is probably more passable than any other camera out there.
07-07-2014, 11:58 AM   #96
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QuoteOriginally posted by clackers Quote
3dB is also quite formally the result of doubling or halving power.
So, if SNR was the only thing to worry about, with a 3dB/stop sensor, you'd be just as well-off setting ISO to base rate and exposing the image in post-processing!
07-07-2014, 01:57 PM   #97
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QuoteOriginally posted by clackers Quote
3dB is also quite formally the result of doubling or halving power
Db are not linear in progression, they are logarithmic. Like sound, if i remember well, the difference between 120 and 121 decibel (the moment you start feeling pain in the ears), seems very little, but in terme of pressure in your ear it's a doubling !

So, back to SNR, 3db is not a single value symbolising a stop. Maybe for low iso, but, as you go up, the value may varie.
07-07-2014, 02:16 PM   #98
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3 dB is half. It's a logarithm, sure, but that's how the equation works out. Do the log (base 10) of 0.5, you get about .3. By convention we multiply by 10.

07-07-2014, 04:56 PM   #99
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Funny what I noticed at Disney. I had the opportunity to take pics for others, with their camera. Granted I saw some serious gear around some folks necks. I carried less in the Army I might say.
But the basic setup (I think or imagine) I pick up Nikon and canon and it is a TOY. It is a light weight plastic toy not much heavier than my point and click.


The professional guy at the character photos, he has a belt, with stuff, and it is HUGE. He tells me, nice camera man.
K-5IIs with DA21.
It is as small as a mirrorless but the pics are awesome, and it weighs five pounds in that configuration. That is quality.
Cheapo plastic stuff isn't. Now I'm talking about those EOS things peeps walk around with of course.
Used as a point and click.
07-09-2014, 04:50 PM - 1 Like   #100
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Concerning the original question, before acquiring my K-5 II I had a Canon 5D with the "L" lenses or Sigma "EX" lenses. I sold it all and went to Pentax because of the smaller & lighter format of the bodies and lenses. I also liked the WR and built in stabilization the Pentax offered. One of the first Pentax lens I got was the DA 55-300 which I quickly returned. I was use to looking through a "L" lens and the quality was not the same. But I like the Pentax primes, and the 18-135 was good enough. Canon "L" lens cost much more, are heavier & larger to lug around, but do deliver good photos. I am very satisfied with my Pentax gear.
07-10-2014, 05:58 AM   #101
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QuoteOriginally posted by Wingincamera Quote
Concerning the original question, before acquiring my K-5 II I had a Canon 5D with the "L" lenses or Sigma "EX" lenses. I sold it all and went to Pentax because of the smaller & lighter format of the bodies and lenses. I also liked the WR and built in stabilization the Pentax offered. One of the first Pentax lens I got was the DA 55-300 which I quickly returned. I was use to looking through a "L" lens and the quality was not the same. But I like the Pentax primes, and the 18-135 was good enough. Canon "L" lens cost much more, are heavier & larger to lug around, but do deliver good photos. I am very satisfied with my Pentax gear.
I'm surprised you found the 55-300 unacceptable, but the 18-135 ok (over the same range, presumably.) Maybe you got a bad copy of the 55-300? Certainly a theoretically perfect 55-300 is not L-level, especially at the longer focal lengths, but it certainly seems to win more universal praise here on the forum than the 18-135.
07-13-2014, 07:27 PM   #102
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I have seen a lot of photographers take fantastic looking pictures with relatively cheap gear. For example in some European and South American countries that are not as wealthy as the USA there are some terrific photographers that make do with entry level cameras and lenses. The thing about good lenses is that they can make an ordinary shot look extraordinary. If you are shooting professionally a good lens kit might be your ticket to getting that job, because believe me people do ask what type of gear you have during an interview.

Last edited by hjoseph7; 07-14-2014 at 06:34 AM.
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