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Author Topic: A7s first impressions  (Read 7363 times)
Ben Rubinstein
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« Reply #20 on: June 17, 2014, 01:29:53 AM »
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Although it's only 12 megapixels, the 5D and D700 for many years and indeed still currently has been all wedding photographers needed. Add that with the almost silent shutter and it's only a shame that it's still got a relatively slow AF compared to the new A6000 system.
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hjulenissen
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« Reply #21 on: June 17, 2014, 02:11:50 AM »
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Sorry folks, but I refuse to become involved in technical discussions where I see something is at odds with theoretical behaviour. It's a no win.
When making subjective claims ("The A7s images appear less noisy to me than the A7 at the same ISO"), there is little need to defend those claims using theory.

When making theoretical claims ("big pixels are less noisy than small ones"), it seems strange to refuse to be involved in theoretical discussions.

-h
« Last Edit: June 17, 2014, 02:14:49 AM by hjulenissen » Logged
laughingbear
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« Reply #22 on: June 17, 2014, 02:56:08 AM »
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Quote: "On the basis of these tests I would judge the A7s to have almost a three stop advantage over the A7r between ISO 6,400 (which is as high as I would use on the A7r)  and ISO 51,200 where the A7s reaches its useful limit (for my type of shooting)."

A7r has about 50% quantum efficiency and the sensors are of similar size.

First of all, image quality is subjective.

That being out of the way, when I saw Den Lennie's Scotland shooting, I spontaneously said to my partner, the A7S will have somewhat usable (read "printable") files up to ISO 50K. Around ISO 25K they are probably a no brainer. Of course that was an out of my guts first impression.

As for dynamic range and pixel size, shooting at higher ISO, it is obvious that large pixel cameras have significantly better dynamic range than small pixel cameras. Now that is not out of my guts, but a hands on observation I can make any time.

I learned over the years that theoretical sensor performance and hands on exposure/print sometimes differ. Remember the Canon G10 causing a stir? How could it be that a G10 produces nearly identical quality on an A3 print of certain (say "intimate landscapes") pictures compared to a high spec Hasselblad? Impossible....not!

Just a few days ago, I read on a forum the opinions that Sony's new developed curved sensor will never make it into a camera, and these opinions were flanked with a lot of theoretical background, some factual, some mixing up terms and conditions, and some claiming underlying physics prohibit the use in a camera.

My gut tells me we will see this sensor in a camera in the next 12 month.  Grin 

Now I quickly leave this field of "thermal noise from dark currents" and shoot some pictures.

Best
Georg



 
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barryfitzgerald
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« Reply #23 on: June 17, 2014, 03:32:18 AM »
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My guess is that he's pointing-out what the camera body has or does not have -- "SteadyShot INSIDETM image stabilization is built into the camera body itself. You'll reduce blur with every A-mount lens because…" (Sony α feature list)

Pretty much I've lenses stretching back to the original Minolta AF range (dated some but many are optically very good)
Losing that isn't great.

The Sony FE 70-200 f/4 G OSS looks nice but is priced high for an f4 lens
Also IBIS is very handy to have with primes. Sony's missed opportunity with A Mount was by not offering a price incentive to customers for lenses without IS/VR. Looking at the pricing strategy for FE lenses I think price to speed is a problem here.

I'm not knocking E mount it is interesting, but not the all in one wonder Sony might think it is.
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bcooter
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« Reply #24 on: June 17, 2014, 10:08:43 AM »
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Michael,

There is very little video information on this camera in testing so I'm curious.

Does the A7s autotrack, or face detect in video mode autofocus?

If so how accurate is the autofocus on video.

In stills does it also autotrack.

And last question, using the A mount adapter (I have A mount Zeiss lenses) does the autofocus work as well as the FE lenses, or work at all?

I'm very interested in this camera for high iso.

Uh one more question.  Will you replace your gh4's with the Sony?

Thx.

BC
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Pete Berry
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« Reply #25 on: June 17, 2014, 11:44:56 AM »
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For the technophiles, DxO's sensor report published today - here's a comparison with the D800e and 5D-III:

http://www.dxomark.com/Cameras/Compare/Side-by-side/Sony-A7S-versus-Canon-EOS-5D-Mark-III-versus-Nikon-D800E___949_795_814

The A7s's DR pulls even with the Nikon's at about measured ISO 600 and takes off from there.

Pete
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michael
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« Reply #26 on: June 17, 2014, 12:17:05 PM »
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I'm an Adobe beta tester, and used a pre-release that has A7s support. As always, every new camera needs to have new support written for its raw files.

The whole DR issue is a tempest in a teapot. There is no standardized way of measuring DR. Sony can claim 15 stops, but unless they tell us what their test criteria are (which they don't) there is no way to corroborate this objectively.

Michael
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ErikKaffehr
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« Reply #27 on: June 17, 2014, 12:40:10 PM »
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Hi,

DR is well defined FWC/Readout noise. That is the definition every one uses. Even Phase One...

Best regards
Erik


I'm an Adobe beta tester, and used a pre-release that has A7s support. As always, every new camera needs to have new support written for its raw files.

The whole DR issue is a tempest in a teapot. There is no standardized way of measuring DR. Sony can claim 15 stops, but unless they tell us what their test criteria are (which they don't) there is no way to corroborate this objectively.

Michael
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Vladimirovich
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« Reply #28 on: June 17, 2014, 01:17:04 PM »
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DR is well defined FWC/Readout noise. That is the definition every one uses. Even Phase One...
but not their dealers & co (some)
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michael
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« Reply #29 on: June 17, 2014, 03:09:01 PM »
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Sorry, but that simply isn't the case.

I have it from several authorities as well as manufacturers themselves that no standardized DR testing exists. Otherwise we wouldn't have the current A7s debacle.

http://www.luminous-landscape.com/essays/the_eyes_have_it.shtml
« Last Edit: June 17, 2014, 04:38:39 PM by michael » Logged
E.J. Peiker
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« Reply #30 on: June 17, 2014, 03:47:50 PM »
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I may be wrong here but it was my understanding that the 15 stop dynamic range that Sony quotes was with an S-log2 gamma curve for video, not a normal still photo curve.
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michael
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« Reply #31 on: June 17, 2014, 04:41:24 PM »
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I may be wrong here but it was my understanding that the 15 stop dynamic range that Sony quotes was with an S-log2 gamma curve for video, not a normal still photo curve.

Possibly, but then how to explain how an 8 bit 4:2:2 image (essentially a video JPG) can have greater dynamic range than a raw file?

Michael
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E.J. Peiker
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« Reply #32 on: June 17, 2014, 04:43:35 PM »
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Yeah, good point.  Even if it is 15 stops, those bottom two or three stops are likely to be very ugly.
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Vladimirovich
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« Reply #33 on: June 17, 2014, 05:20:11 PM »
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Yeah, good point.  Even if it is 15 stops, those bottom two or three stops are likely to be very ugly.
the same logic applies to 13 stops DR or 11 stops DR cameras... so those extras stops are valuable (not that they are even there based on DxOMark engineering criteria)
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Vladimirovich
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« Reply #34 on: June 17, 2014, 05:20:30 PM »
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Possibly, but then how to explain how an 8 bit 4:2:2 image (essentially a video JPG) can have greater dynamic range than a raw file?

Michael

because there is NR
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Vladimirovich
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« Reply #35 on: June 17, 2014, 05:22:20 PM »
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I have it from several authorities as well as manufacturers themselves that no standardized DR testing exists.
true - some "magazines" post "DR" numbers based on raw conversion/post processing with heavy NR applied
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jani
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« Reply #36 on: June 18, 2014, 01:13:38 AM »
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Thanks for the first impressions, Michael, useful insight as ever!

Minor nitpick:

"Dandylion & Swing" - the spelling is "dandelion", and the flower is a daisy. Smiley

(Nice going - away from the forums for years, and back with a nitpick …)
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Jan
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« Reply #37 on: June 18, 2014, 05:23:31 AM »
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Hi Michael,

Thanks for the info. I don't say that Sony A7s has > 15 EV of DR, just that there is a technical definition of DR that is common to DxO, Kodak and Dalsa Spec Sheets and specs by Phase One. As far as I recall they used to be within 0.3 EV. The figures DxO shows are normally normalized to 8 MP, so to get consistent data we need to look at the "screen-mode" values.

DR is hard to measure, mostly because of lens flare affecting the results. Arri has developed a method for accurately measure DR using a special target and special software.

DR can be found analytically by using several exposures and calculate the involved parameters.

I would add that I looked at the Sony A7s results at DxO and they are very odd. The A7s sensor is definitively a different animal from say the A7r sensor.

A final point, DR is essentially about shadow noise, especially if we expose ETTR. It does say about the amount of noise but little about the quality of the noise. It can be smooth or harsh.

Best regards
Erik

Sorry, but that simply isn't the case.

I have it from several authorities as well as manufacturers themselves that no standardized DR testing exists. Otherwise we wouldn't have the current A7s debacle.

http://www.luminous-landscape.com/essays/the_eyes_have_it.shtml

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BartvanderWolf
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« Reply #38 on: June 18, 2014, 05:30:02 AM »
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I have it from several authorities as well as manufacturers themselves that no standardized DR testing exists.

Hi Michael,

Those spokespersons are wrong.

DR is well defined FWC/Readout noise. That is the definition every one uses.

Correct. It's the maximum possible DR that the sensor can record, it's called engineering Dynamic Range, and is universally understood throughout the industry.

The only confusion possible is about how much of that maximum range is usable to a photographer, and that is because of the shadow noise, which for different folks is still acceptable at different levels. The acceptability of a certain level of noise also depends on the amount of noise reduction one is willing or able to apply without hurting the finest detail too much.

BTW, the DxOMark score is available, and the A7S scores 12.85 EV dynamic range at ISO 50 (marginally better than at ISO 100), before any scaling for print size.

All the rest that is done to an image, including the quantification with a non-linear response curve, is post-processing to better allow boosting of the local or overall contrast, which can be very effective if the engineering DR is relatively high, as it is in the A7s.

Cheers,
Bart
« Last Edit: June 18, 2014, 05:56:52 AM by BartvanderWolf » Logged
michael
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« Reply #39 on: June 18, 2014, 07:04:24 AM »
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I used Lightroom 5.5...a prerelease with A7s support.

Cheers,

Michael
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