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Author Topic: A7s first impressions  (Read 7999 times)
Aku Ankka
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« on: June 16, 2014, 10:01:50 AM »
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First, please don't take any of this personally. I envy you photographic skills and the fact you get all these nice toys to play with Smiley
But I do have something to comment:

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. Even if the read noise of the A7s is somewhat lower than that of A7r (which is likely on image level), outside of the areas with extremely little light (only a handful of photons per pixel), it would need to have several times higher QE than the ~50% of A7r to be as good as the article claims. This is of course impossible.

Additionally your test images don't agree with your text.

In practice what the above means is that throughout the usable range the midtones and highlights have similar quality, but in the very deepest shadows A7s likely have a slight advantage. (Of course in video there is dramatic difference as A7s doesn't skip pixels/lines.)

How the image data (ie. raw file) is processed of course plays big part. One should take advantage of the large pixel count of A7r and perform noise reduction before downsizing as downsizing alone is horribly inefficient way to doing NR. Downsizing is of course needed for comparison, just like you did, good!

Quote: "They offer large pixels (greater dynamic range and colour depth)"

Large pixels offer large DR for the pixel, but at the level of the image, which is the interest of photographers they typically offer lower DR. This is because signal and noise do not add up the same way (noise adds in quadrature). One needs to normalize the DR measurements for the same print size. The same goes for colour depth (whatever that means) and tonality and almost all metrics.

(On the other hand you did notice that there was no noticeable and/or significant difference between the DR of A7s and A7r which is likely correct.)

Quote: "A significant addition to the A7s over its earlier siblings is an electronic front curtain shutter. This makes the camera completely silent"

A7 has EFC as well and it's not the feature which makes the camera silent. It's the full electonic shutter which is the reason (both curtains).

Two questions:

I wonder about the silent mode: how visible is the rolling shutter jollo effect for stills (I assume there is no global shutter, but only rolling one)? This is very interesting feature regardless.

Is the viewfinder image better in low light than it is in the other A7-series cameras? I imagine this could be due to far superior live-feed from the sensor.

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Vladimirovich
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« Reply #1 on: June 16, 2014, 10:29:02 AM »
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A7 has EFC as well
as far as I remember specs neither A7r __nor___ A7s have EFCS - only A7 has that.
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michael
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« Reply #2 on: June 16, 2014, 10:37:03 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.

Michael


Ps: Wait a few days till some of the review sites that have testing labs publish their results. I'm guessing that theory and reality are going to collide.  Wink

Michael
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Isaac
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« Reply #3 on: June 16, 2014, 11:13:04 AM »
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Thanks for the review, once again your curiosity and fascination with photography illuminates.
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Vladimirovich
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« Reply #4 on: June 16, 2014, 11:26:46 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.

presence of EFCS is not a technical discussion - it is simply a matter of official specifications - it is either there or not... no formulas, DxOMark measurements or personal impressions... plus by defintion EFCS still involves mechanical shutter operation in the process, so it again by that simple fact can't be totally silent.
« Last Edit: June 16, 2014, 11:28:48 AM by Vladimirovich » Logged
zlatko-b
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« Reply #5 on: June 16, 2014, 11:47:13 AM »
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How well does the regular A7 do in terms of high ISO performance for stills?  Is it right in between the A7s  and the A7r?  Looking at the specs, the A7 seems like a nice compromise between the 12mp A7s and the 36mp A7r, and it has the added attraction of being the least expensive.
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barryfitzgerald
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« Reply #6 on: June 16, 2014, 01:37:08 PM »
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Interesting article. I think of some interest for video folks, possibly low light specialist shooters, more a niche product really
I'm not convinced the format and body design or e mount itself  is appealing to many with the exception of travel shooters. Of course being a long time Minolta user I admit I'm far from unbiased.



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jjj
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« Reply #7 on: June 16, 2014, 02:23:46 PM »
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Michael, I see your comments about the A7s's MF-esque images have been noticed by Petapixel with a clickbaity [is that even a word?] headline added.
« Last Edit: June 16, 2014, 02:27:13 PM by jjj » Logged

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Vladimirovich
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« Reply #8 on: June 16, 2014, 02:26:11 PM »
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or e mount itself 
how does E mount by itself be applealing to travel shooters only ?
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barryfitzgerald
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« Reply #9 on: June 16, 2014, 02:46:23 PM »
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how does E mount by itself be applealing to travel shooters only ?

I didn't say that I use A mount so my view won't match everyone's but all my glass is stabilised on A Mount, nothing is on E mount (this is pretty big for me maybe not others)
Second point..A mount users can buy the adapter, but it adds bulk and few would invest in E mount lenses as you can't put E mount glass on A Mount

Main attraction for E mount is legacy MF glass with adapters. The lens selection on that mount is both limited and expensive.
It's a somewhat flawed strategy overall from Sony they might get people to buy the bodies, but they will have a job selling lots of lenses (which is where the big profits are)

There are other downers too, which I think limit the appeal to Canikon users.

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michael
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« Reply #10 on: June 16, 2014, 04:05:20 PM »
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Michael, I see your comments about the A7s's MF-esque images have been noticed by Petapixel with a clickbaity [is that even a word?] headline added.

A bit sensational quoted that way, somewhat out of context, but at least they spelled my name right.  Wink
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Jim Kasson
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« Reply #11 on: June 16, 2014, 04:30:18 PM »
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I didn't say that I use A mount so my view won't match everyone's but all my glass is stabilised on A Mount, nothing is on E mount

The Sony FE 70-200 f/4 G OSS is stabilized, and quite nicely, too. Or did you mean that none of the E mount lenses you own are stabilized?

Jim
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Isaac
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« Reply #12 on: June 16, 2014, 04:57:22 PM »
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Or did you mean that none of the E mount lenses you own are stabilized?

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)
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Vladimirovich
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« Reply #13 on: June 16, 2014, 05:52:16 PM »
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I didn't say that I use A mount so my view won't match everyone's but all my glass is stabilised on A Mount, nothing is on E mount (this is pretty big for me maybe not others)
Second point..A mount users can buy the adapter, but it adds bulk and few would invest in E mount lenses as you can't put E mount glass on A Mount

Main attraction for E mount is legacy MF glass with adapters. The lens selection on that mount is both limited and expensive.
It's a somewhat flawed strategy overall from Sony they might get people to buy the bodies, but they will have a job selling lots of lenses (which is where the big profits are)

There are other downers too, which I think limit the appeal to Canikon users.



you forgot that E-mount itself is the same for Sony's APS-C cameras too and there are many existing APS-C cameras with that same exactly E-mount... so you had to put some strings attached to the posting
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jjj
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« Reply #14 on: June 16, 2014, 06:13:28 PM »
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A bit sensational quoted that way, somewhat out of context, but at least they spelled my name right.  Wink
Sadly the muppets in the peanut gallery are now however judging you by the rather inaccurate headline. Because actually reading what you wrote would be too much effort.
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michael
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« Reply #15 on: June 16, 2014, 07:23:59 PM »
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After 15 years of this the muppets rarely disappoint.

Michael
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David Anderson
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« Reply #16 on: June 16, 2014, 08:20:42 PM »
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Interesting - thanks for the review LL.
I will hand it to Sony, as stated in the review, they seem to always be pushing new dirt and they have my attention.
The A7 series is seriously tempting for it's small size.
Ok, I'm surprised by the camera having a FF 12 MP sensor - I would have thought that too low these days - but the big players like Sony probably have better intel on the future of photography than I do.  Wink





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dreed
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« Reply #17 on: June 16, 2014, 09:02:47 PM »
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One point I picked up on was that you find the DR of the A7s comparable to Sony's other cameras (of about 14 stops) ... quite a few people are wondering if they'll be able to deliver on the 15.3 stops of DR as they claim on the product page and clearly not.

Oh! Before I forget... two important points I don't recall from your review...

Are the Sony A7s raw files the same as Sony's other cameras or are they using a new raw file format?
Have you been able to do raw file processing with LR/PS or do you need to use Sony-ware?
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ErikKaffehr
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« Reply #18 on: June 16, 2014, 11:41:02 PM »
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Hi,

Using same generation technology the DR is dependent on sensor size mostly. Larger pixels have more DR per pixel, but the way Michael compares the A7s and A7r the pixels are essentially normalised. More pixels means less noise in print.

I would say that Michaels way to compare the images is the correct way, albeit it ignores resolution. My preferred method is to resize to a planned print size, like A2 at 180PPI (which seems to be a good requirement according to Bruce Fraser/Jeff Schwe) or 70x100 cm at 200 PPI which is recommended by my printing lab. The differences in print will always be much smaller than on screen.

The points that Aku Anka makes are valid in my view.

Nice to see Sony on the go, but I am waiting for an A9, with 54 MP sensor, larger battery and no shutter vibrations.

Best regards
Erik

One point I picked up on was that you find the DR of the A7s comparable to Sony's other cameras (of about 14 stops) ... quite a few people are wondering if they'll be able to deliver on the 15.3 stops of DR as they claim on the product page and clearly not.

Oh! Before I forget... two important points I don't recall from your review...

Are the Sony A7s raw files the same as Sony's other cameras or are they using a new raw file format?
Have you been able to do raw file processing with LR/PS or do you need to use Sony-ware?
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BernardLanguillier
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« Reply #19 on: June 17, 2014, 12:08:53 AM »
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Thanks for the comparison Michael.

If I may, what raw converter did you use this time around?

I believe that DxO doesn't support the a7s, but I have been standardizing all my high ISO images on DxO Prime technology for a few months since it does IMHO deliver the best outputs. My RX100 ISO3200 images look great through PRIME for example.

I think that it could be interesting to revisit this a7s/a7r high ISO image quality with Prime used once DxO decides to support the a7s. ISO 6400 and 12800 would probably be enough.

Cheers,
Bernard
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A few images online here!
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