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Site & Board Matters => About This Site => Topic started by: Aku Ankka on June 16, 2014, 11:01:50 am

Title: A7s first impressions
Post by: Aku Ankka on June 16, 2014, 11:01:50 am
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 :)
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.

Title: Re: A7s first impressions
Post by: Vladimirovich on June 16, 2014, 11:29:02 am
A7 has EFC as well
as far as I remember specs neither A7r __nor___ A7s have EFCS - only A7 has that.
Title: Re: A7s first impressions
Post by: michael on June 16, 2014, 11:37:03 am
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.  ;)

Michael
Title: Re: A7s first impressions
Post by: Isaac on June 16, 2014, 12:13:04 pm
Thanks for the review, once again your curiosity and fascination with photography illuminates.
Title: Re: A7s first impressions
Post by: Vladimirovich on June 16, 2014, 12:26:46 pm
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.
Title: Re: A7s first impressions
Post by: zlatko-b on June 16, 2014, 12:47:13 pm
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.
Title: Re: A7s first impressions
Post by: barryfitzgerald on June 16, 2014, 02:37:08 pm
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.



Title: Re: A7s first impressions
Post by: jjj on June 16, 2014, 03:23:46 pm
Michael, I see your comments about the A7s's MF-esque images have been noticed by Petapixel (http://petapixel.com/2014/06/16/report-claims-sony-a7s-image-quality-comparable-medium-format/) with a clickbaity [is that even a word?] headline added.
Title: Re: A7s first impressions
Post by: Vladimirovich on June 16, 2014, 03:26:11 pm
or e mount itself 
how does E mount by itself be applealing to travel shooters only ?
Title: Re: A7s first impressions
Post by: barryfitzgerald on June 16, 2014, 03:46:23 pm
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.

Title: Re: A7s first impressions
Post by: michael on June 16, 2014, 05:05:20 pm
Michael, I see your comments about the A7s's MF-esque images have been noticed by Petapixel (http://petapixel.com/2014/06/16/report-claims-sony-a7s-image-quality-comparable-medium-format/) 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.  ;)
Title: Re: A7s first impressions
Post by: Jim Kasson on June 16, 2014, 05:30:18 pm
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
Title: Re: A7s first impressions
Post by: Isaac on June 16, 2014, 05:57:22 pm
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)
Title: Re: A7s first impressions
Post by: Vladimirovich on June 16, 2014, 06:52:16 pm
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
Title: Re: A7s first impressions
Post by: jjj on June 16, 2014, 07:13:28 pm
A bit sensational quoted that way, somewhat out of context, but at least they spelled my name right.  ;)
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.
Title: Re: A7s first impressions
Post by: michael on June 16, 2014, 08:23:59 pm
After 15 years of this the muppets rarely disappoint.

Michael
Title: Re: A7s first impressions
Post by: David Anderson on June 16, 2014, 09:20:42 pm
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.  ;)





Title: Re: A7s first impressions
Post by: dreed on June 16, 2014, 10:02:47 pm
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?
Title: Re: A7s first impressions
Post by: ErikKaffehr on June 17, 2014, 12:41:02 am
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?
Title: Re: A7s first impressions
Post by: BernardLanguillier on June 17, 2014, 01:08:53 am
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
Title: Re: A7s first impressions
Post by: Ben Rubinstein on June 17, 2014, 02:29:53 am
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.
Title: Re: A7s first impressions
Post by: hjulenissen on June 17, 2014, 03:11:50 am
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
Title: Re: A7s first impressions
Post by: laughingbear on June 17, 2014, 03:56:08 am
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.  ;D 

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

Best
Georg



 
Title: Re: A7s first impressions
Post by: barryfitzgerald on June 17, 2014, 04:32:18 am
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.
Title: Re: A7s first impressions
Post by: bcooter on June 17, 2014, 11:08:43 am
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
Title: Re: A7s first impressions
Post by: Pete Berry on June 17, 2014, 12:44:56 pm
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
Title: Re: A7s first impressions
Post by: michael on June 17, 2014, 01:17:05 pm
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
Title: Re: A7s first impressions
Post by: ErikKaffehr on June 17, 2014, 01:40:10 pm
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
Title: Re: A7s first impressions
Post by: Vladimirovich on June 17, 2014, 02:17:04 pm
DR is well defined FWC/Readout noise. That is the definition every one uses. Even Phase One...
but not their dealers & co (some)
Title: Re: A7s first impressions
Post by: michael on June 17, 2014, 04:09:01 pm
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 (http://www.luminous-landscape.com/essays/the_eyes_have_it.shtml)
Title: Re: A7s first impressions
Post by: E.J. Peiker on June 17, 2014, 04:47:50 pm
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.
Title: Re: A7s first impressions
Post by: michael on June 17, 2014, 05:41:24 pm
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
Title: Re: A7s first impressions
Post by: E.J. Peiker on June 17, 2014, 05:43:35 pm
Yeah, good point.  Even if it is 15 stops, those bottom two or three stops are likely to be very ugly.
Title: Re: A7s first impressions
Post by: Vladimirovich on June 17, 2014, 06:20:11 pm
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)
Title: Re: A7s first impressions
Post by: Vladimirovich on June 17, 2014, 06:20:30 pm
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
Title: Re: A7s first impressions
Post by: Vladimirovich on June 17, 2014, 06:22:20 pm
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
Title: Re: A7s first impressions
Post by: jani on June 18, 2014, 02:13:38 am
Thanks for the first impressions, Michael, useful insight as ever!

Minor nitpick:

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

(Nice going - away from the forums for years, and back with a nitpick …)
Title: Re: A7s first impressions
Post by: ErikKaffehr on June 18, 2014, 06:23:31 am
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 (http://www.luminous-landscape.com/essays/the_eyes_have_it.shtml)

Title: Re: A7s first impressions
Post by: Bart_van_der_Wolf on June 18, 2014, 06:30:02 am
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 (http://www.ccd.com/ccd111.html), 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 (http://www.dxomark.com/Cameras/Sony/A7S---Measurements) 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
Title: Re: A7s first impressions
Post by: michael on June 18, 2014, 08:04:24 am
I used Lightroom 5.5...a prerelease with A7s support.

Cheers,

Michael
Title: Re: A7s first impressions
Post by: michael on June 18, 2014, 08:09:45 am
Bart,

Sony uses Engineering Dynamic Range. DxO uses 1:1 S/N. So, not directly comparable.

The important point, to my view, is not the absolute measured number under either schema, by rather the comparative numbers.

DxO now has S/N analysis for some 270 cameras of all brands. These are self consistent and done by one lab presumably using the same methodology.

On that basis the A7s simply is not what many people hoped it would be. That's really what the whole debate is about.

Michael
Title: Re: A7s first impressions
Post by: ErikKaffehr on June 18, 2014, 08:21:20 am
Hi Michael,

The definition of egineering DR is SNR=1.

I would agree that the DXO data does indicate that the A7s is a bit weak in DR at base ISO. On the other hand it seems to excel at high ISO. It is more like Canon than Nikon/Sony/Pentax in that sense, somewhat fishy in my view.

It may be that the A7s is more oriented towards high ISO and motion than low ISO and stills.

Let's put it this way, nothing in the DxO data makes me long for an A7s.

Best regards
Erik

Bart,

Sony uses Engineering Dynamic Range. DxO uses 1:1 S/N. So, not directly comparable.

The important point, to my view, is not the absolute measured number under either schema, by rather the comparative numbers.

DxO now has S/N analysis for some 270 cameras of all brands. These are self consistent and done by one lab presumably using the same methodology.

On that basis the A7s simply is not what many people hoped it would be. That's really what the whole debate is about.

Michael

Title: Re: A7s first impressions
Post by: dreed on June 18, 2014, 09:37:23 am
Hi Michael,

The definition of egineering DR is SNR=1.

I would agree that the DXO data does indicate that the A7s is a bit weak in DR at base ISO. On the other hand it seems to excel at high ISO. It is more like Canon than Nikon/Sony/Pentax in that sense, somewhat fishy in my view.

It may be that the A7s is more oriented towards high ISO and motion than low ISO and stills.

And thus the sensor/camera is built differently - rather than have an on-sensor ADC (like it is with the 36MP sensor), the ADC is offboard like it is with Canon's DSLRs?
Title: Re: A7s first impressions
Post by: ErikKaffehr on June 18, 2014, 09:54:03 am
Hi,

I don't have the slightest idea. The DR at base ISO seems a bit bad for a fat pixel sensor. I guess Sony still has on chip ADCs but they play with on chip noise reduction.

Possibly, the chip is optimised for fast readout (for video), giving up a bit on maximum DR?

Best regards
Erik


And thus the sensor/camera is built differently - rather than have an on-sensor ADC (like it is with the 36MP sensor), the ADC is offboard like it is with Canon's DSLRs?
Title: Re: A7s first impressions
Post by: Vladimirovich on June 18, 2014, 10:54:49 am

DR is hard to measure, mostly because of lens flare affecting the results.

as far as I remember DxO photos illustrating their process they do not use lens during that test - they do illuminate sensor in camera directly and they do not measure sensor DR - they measure "camera's" DR, so whatever reflections are in chamber housing a sensor are not supposed to be totally absent.
Title: Re: A7s first impressions
Post by: Vladimirovich on June 18, 2014, 10:56:50 am
And thus the sensor/camera is built differently - rather than have an on-sensor ADC (like it is with the 36MP sensor), the ADC is offboard like it is with Canon's DSLRs?
ADCs can still be on board but might be designed in a different way vs regular Sony tech
Title: Re: A7s first impressions
Post by: Vladimirovich on June 18, 2014, 10:57:50 am
Possibly, the chip is optimised for fast readout (for video), giving up a bit on maximum DR?

fast readout for video (and electronic shutter for stills) is achieved by switching ADCs in 10bit mode
Title: Re: A7s first impressions
Post by: Ben Rubinstein on June 18, 2014, 11:22:20 am
What would be interesting is to see what DR Sony claimed for the A7r and then compare to their claim for the A7s. With whatever methodology they use the ratio should be similar should it not?
Title: Re: A7s first impressions
Post by: Jim Kasson on June 18, 2014, 12:12:20 pm
ADCs can still be on board but might be designed in a different way vs regular Sony tech

Not only the ADC could be different. Take a look at the white paper pointed to by this link:

http://www.aptina.com/products/technology/DR-Pix_WhitePaper.pdf

Unfortunately -- at least for my perspective -- it seems that it was written by a product manager, not an engineer, but it does offer two interesting -- again, at least for me -- insights.

The first is the separation of dynamic range into Intra-scene DR and Inter-scene DR. I've been working with ISO-less sensors almost exclusivly for the last couple of years, so the distinction is a little jarring to me, but those of you who work with Canons will be able to get your head around it more easily.

The second is the idea that the operation of the sensor ship could be configured with the ISO knob in ways other than changing the pre-ADC gain and the ADC resolution. This latter notion may explain some of the a7S performance, because it appears to me that the inter-scene DR can't be explained easily by read noise and the intra-scene DR.

I have an a7S on order and will test and report when it arrives.

Jim
Title: Re: A7s first impressions
Post by: dbateman on June 18, 2014, 03:42:56 pm
Micheal, You have a great article.  And I respect you.

The think I want to comment on is DXO is not showing us really what the pixel peepers want to see in the summary table which really doesn't reflect their data.  If you do a comparison of A7s, A7r and Olympus EM1 and look at the actual graphs you will see on the default print setting the A7r is above in DR.  But this is taking a 36Mp sensor in shrinking it "magically" to 8Mpixels for a print.  Cropers like me and the pixel peepers (your peanut gallery) like to click the Screen option for all the graphs.  Now not surprisingly the A7r is the same as the Olympus EM1 and the A7s actually is the best.  And by the best by a large margin.  So if you don't print a 8Mpixel or you display your stuff on high resolution screens or you crop you photo to get the correct frame.  Then you would see the A7s is very good. 
But you are fully correct!  The A7s does NOT have 15 stops DR is more like 13 and equal to the A7r at base ISO.  But at 800 ISo the DR is 11.7 for A7s and 10.7 for A7r, and the A7r just matches the EM1!  Amazing the DR at 25600 is 8.75 for the A7s, where as its 6.4 for both the EM1 and A7r!
So click the screen option to see the real results!
All the best,
David.
Title: Re: A7s first impressions
Post by: barryfitzgerald on June 18, 2014, 04:21:22 pm
Evidently DxO have not been able to measure the DR of Fuji sensors in the past (from what I gather)
What counts more isn't the numbers, but real world shooting.

Charts bore me..real stuff is far more revealing
Title: Re: A7s first impressions
Post by: ErikKaffehr on June 18, 2014, 04:32:02 pm
Hi,

Screen is pixel peeping and print corresponds to print, simple as that. But if Sony says 15.3 EV without qualification, it is a marketing trueth AKA known as a lie.

Best regards
Erik

Micheal, You have a great article.  And I respect you.

The think I want to comment on is DXO is not showing us really what the pixel peepers want to see in the summary table which really doesn't reflect their data.  If you do a comparison of A7s, A7r and Olympus EM1 and look at the actual graphs you will see on the default print setting the A7r is above in DR.  But this is taking a 36Mp sensor in shrinking it "magically" to 8Mpixels for a print.  Cropers like me and the pixel peepers (your peanut gallery) like to click the Screen option for all the graphs.  Now not surprisingly the A7r is the same as the Olympus EM1 and the A7s actually is the best.  And by the best by a large margin.  So if you don't print a 8Mpixel or you display your stuff on high resolution screens or you crop you photo to get the correct frame.  Then you would see the A7s is very good. 
But you are fully correct!  The A7s does NOT have 15 stops DR is more like 13 and equal to the A7r at base ISO.  But at 800 ISo the DR is 11.7 for A7s and 10.7 for A7r, and the A7r just matches the EM1!  Amazing the DR at 25600 is 8.75 for the A7s, where as its 6.4 for both the EM1 and A7r!
So click the screen option to see the real results!
All the best,
David.
Title: Re: A7s first impressions
Post by: fdisilvestro on June 18, 2014, 06:23:02 pm
But if Sony says 15.3 EV without qualification, it is a marketing trueth AKA known as a lie.


Nothing new, Epson has always claimed their V700 scanners capable of 6400 dpi resolution and I have never seen any test that reached even half of it.

I think that the high ISO capability of the A7s is impressive, at least 1 stop above the closest competitors.

My take:
Marketing: how much better is this camera?
Engineering: 1 stop better at high ISO
Marketing thought: if previous cameras had 14 stops DR then this must be at least 15  :D :D
 
Jokes aside, if you extrapolate the curve from high ISO (as if it were a ISO-less sensor) this camera could actually reach easily above 15 stops DR
Title: Re: A7s first impressions
Post by: Vladimirovich on June 18, 2014, 06:25:48 pm
Evidently DxO have not been able to measure the DR of Fuji sensors in the past (from what I gather)
I 'd not use the wording "have not been able to measure", they simply do not want to invest time/effort yet (may be they hope that Fuji will come to senses and drop x-trans marketing trick when moves to 24mp)
Title: Re: A7s first impressions
Post by: Vladimirovich on June 18, 2014, 06:27:37 pm
But if Sony says 15.3 EV without qualification, it is a marketing trueth AKA known as a lie.
and ".3" instead of ".99" shall make that more technically sound  ;)
Title: Re: A7s first impressions
Post by: dreed on June 19, 2014, 07:20:20 am
Jokes aside, if you extrapolate the curve from high ISO (as if it were a ISO-less sensor) this camera could actually reach easily above 15 stops DR

You'd need a raw file that was capturing 16bits per colour channel to do DR of 15.3.

Title: Re: A7s first impressions
Post by: fdisilvestro on June 19, 2014, 10:17:47 am
You'd need a raw file that was capturing 16bits per colour channel to do DR of 15.3.



Only if you use linear encoding. Sony has been using non-linear encoding in other cameras already
Title: Re: A7s first impressions
Post by: bjanes on June 19, 2014, 01:57:31 pm
Correct. It's the maximum possible DR that the sensor can record, it's called engineering Dynamic Range (http://www.ccd.com/ccd111.html), 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.

Bart,

There is one point about the DXO dynamic range calculation as compared to engineering DR that has always confused me. A common method of determining the read noise of a sensor is to put the lens cap on and take a dark frame. Read noise and shot noise combine in quadrature and with the lens cap on there is no shot noise and the read noise is the output of the sensor (provided that the read noise is not clipped as with Nikon cameras). A SNR of one indicates that some signal is present. Does the signal refer to the input or output of the sensor?

As an example, assume that the read noise of a sensor is 10 electrons. If the photons incident on the sensel releases 10 electrons, the shot noise would be sqrt(10) or 3.16 electrons. Total noise would be sqrt(10^2 + 10) or 10.49 electrons. If one uses 10 electrons as the signal, the SNR would be 1.049, hardly different from 1.0.

Bill
Title: Re: A7s first impressions
Post by: Fine_Art on June 20, 2014, 12:31:20 am
Only if you use linear encoding. Sony has been using non-linear encoding in other cameras already

Please explain what you mean by that. I thought RAW was the numerical representation of the pixel charge. Jpg was a log scaled translation into 8 bits. What do you mean by encoding in raw?
Title: Re: A7s first impressions
Post by: dreed on June 20, 2014, 03:07:08 am
Please explain what you mean by that. I thought RAW was the numerical representation of the pixel charge. Jpg was a log scaled translation into 8 bits. What do you mean by encoding in raw?

It is a linear representation of the pixel charge.

Title: Re: A7s first impressions
Post by: fdisilvestro on June 20, 2014, 03:22:22 am
Please explain what you mean by that. I thought RAW was the numerical representation of the pixel charge. Jpg was a log scaled translation into 8 bits. What do you mean by encoding in raw?

Raw contains numerical values of the output af an analog to digital conversion. When a constant quantization step is used, you get a linear encoding of the values. This is the common and easiest approach. The issue with linear encoding is that it is very inefficient at high values and scarce at low values (eg only few bits for the shadows and to many for the highlights)
If you change to a variable quantization step, smaller for low signals and taller for high values, then you use more bits in the shadows and enough bits in the highlights. With this type of encoding there is no more a 1:1 relation in the bits needed to represent a specific dynamic range.
Title: Re: A7s first impressions
Post by: ErikKaffehr on June 20, 2014, 04:21:23 am
Thanks for explanation, much better than what I have managed.

Best regards
Erik

Raw contains numerical values of the output af an analog to digital conversion. When a constant quantization step is used, you get a linear encoding of the values. This is the common and easiest approach. The issue with linear encoding is that it is very inefficient at high values and scarce at low values (eg only few bits for the shadows and to many for the highlights)
If you change to a variable quantization step, smaller for low signals and taller for high values, then you use more bits in the shadows and enough bits in the highlights. With this type of encoding there is no more a 1:1 relation in the bits needed to represent a specific dynamic range.
Title: Re: A7s first impressions
Post by: Bart_van_der_Wolf on June 20, 2014, 06:05:06 am
There is one point about the DXO dynamic range calculation as compared to engineering DR that has always confused me. A common method of determining the read noise of a sensor is to put the lens cap on and take a dark frame. Read noise and shot noise combine in quadrature and with the lens cap on there is no shot noise and the read noise is the output of the sensor (provided that the read noise is not clipped as with Nikon cameras). A SNR of one indicates that some signal is present. Does the signal refer to the input or output of the sensor?

Hi Bill,

That's how I do it if it needs to be done accurately. I even exclude the possibility of lens electronics interfering, by using the body cap. I also cover the viewfinder in order to prevent light leaking into the mirrorbox. I also use the shortest possible exposure time (1/8000th sec.) to reduce temporal/thermal noise build-up. To also eliminate pattern noise, one should subtract two such black-frame exposures, and correct the StDev by dividing by Sqrt(2).

Since we cannot know if and how analog gain is employed, we'll have to empirically/statistically determine the input signal in electrons (e-) from the sensor output in ADU or DN, corrected for the gain. However, this will only work if the Raw data (ADUs) is not clipped to (presumably) zero by eliminating any Blackpoint Offset. For example Canon cameras allow to analyze the full black-frame noise, and e.g. Nikon cameras typically clip the black-frame noise. In addition, some manufacturers (e.g. Sony) have started adding additional processing to record the ADUs with a non-linear response-curve in some of their camera models.

This all complicates testing (it's not practical to switch testing methods between models), and is part of the reason that DxO use a somewhat different method, at least that is what I have read between the lines. Apparently (http://forum.dxomark.com/index.php/topic,2414.msg4341.html#msg4341), they use the least exposed parts of the SNR curves to extrapolate and determine the black-point at dB=0 (SNR=1, because 20*Log(1) = 0 dB) or, sometimes if that is not a typo, dB=1 (SNR=1.122, because 20*Log(1.122)=1 dB). They do also calibrate for actual exposure by measuring the actual influx of light, and ISO sensitivity. They seem to use a lens on the bodies, but they only shoot one exposure level at a time (by blocking the other filters in their setup), so glare should not play a role.

My findings with the laborious method of subtracting pairs of images and deriving gain from the slope of the response curve to calculate electron input, corresponds to within approx. 0.1 EV with the DxO findings on Dynamic Range.

Cheers,
Bart
Title: Re: A7s first impressions
Post by: fdisilvestro on June 20, 2014, 06:50:00 am
In Nikon cameras, the masked pixels are not clipped, you can use those for your calculations.
Title: Re: A7s first impressions
Post by: Bart_van_der_Wolf on June 20, 2014, 07:49:42 am
In Nikon cameras, the masked pixels are not clipped, you can use those for your calculations.

Correct, I forgot to add that.

There is however a benefit to sampling actual image sensels. The actual sensels being used for image capture may be affected by surrounding electronics (e.g. amplifier glow), and pattern noise. By only using a narrow strip of masked sensels on one side of the sensor array, we may get a somewhat biased (positive or negative) outlook. Also important is to determine if the row/column directly adjacent to the unmasked sensels is not affected by cross-talk or light leakage. It's sometimes better to not include that 1 pixel row/column of the multiple row/column masked area.

Cheers,
Bart
Title: Re: A7s first impressions
Post by: fdisilvestro on June 20, 2014, 07:41:51 pm
I also use the shortest possible exposure time (1/8000th sec.) to reduce temporal/thermal noise build-up.


Bart,

I'm not sure if it really makes a difference using a shutter speed above x-sync (e.g.1/250) unless the sensor is "turned off" as soon as the second curtain closes (I don't really know how long the sensor is active in cameras with physical shutter).
Title: Re: A7s first impressions
Post by: Jim Kasson on June 20, 2014, 07:56:59 pm
I'm not sure if it really makes a difference using a shutter speed above x-sync (e.g.1/250) unless the sensor is "turned off" as soon as the second curtain closes (I don't really know how long the sensor is active in cameras with physical shutter).

Good point. I always did like Bart does, but never thought much about it. I guess it can't hurt anything.

Jim
Title: Re: A7s first impressions
Post by: Bart_van_der_Wolf on June 20, 2014, 08:10:06 pm
I'm not sure if it really makes a difference using a shutter speed above x-sync (e.g.1/250) unless the sensor is "turned off" as soon as the second curtain closes (I don't really know how long the sensor is active in cameras with physical shutter).

Hi Frank,

I have no timing details, but it makes sense to off-load the image data as soon as the second shutter curtain closes, to allow resetting the sensor for the next frame in case of continuous shooting. I do know that on my 1Ds3 I can only change the timing between pressing the shutter release/mirror-up and the opening of the first shutter curtain (to allow resetting the sensor and closing the aperture), but not the time afterwards, so I assume it is ASAP (why wait).

Cheers,
Bart
Title: Re: A7s first impressions
Post by: Fine_Art on June 20, 2014, 10:03:41 pm
Raw contains numerical values of the output af an analog to digital conversion. When a constant quantization step is used, you get a linear encoding of the values. This is the common and easiest approach. The issue with linear encoding is that it is very inefficient at high values and scarce at low values (eg only few bits for the shadows and to many for the highlights)
If you change to a variable quantization step, smaller for low signals and taller for high values, then you use more bits in the shadows and enough bits in the highlights. With this type of encoding there is no more a 1:1 relation in the bits needed to represent a specific dynamic range.

Very interesting, thanks. Is there a description of the curve they use somewhere?
Title: Re: A7s first impressions
Post by: Vladimirovich on June 21, 2014, 11:57:41 am
Very interesting, thanks. Is there a description of the curve they use somewhere?

if the question is about Sony then for example :

http://blog.lexa.ru/2014/02/02/rawdigger_103_raskapyvaya_sony.html
http://blog.lexa.ru/2014/01/25/o_bitnosti_u_kamer_sony.html
http://blog.lexa.ru/2014/01/22/pro_sony_a900_i_compressed_raw.html
http://blog.lexa.ru/2012/12/29/o_sortakh_raw_u_sony.html
http://blog.lexa.ru/2011/10/28/o_lineinosti_raw_i_ettr.html
Title: Re: A7s first impressions
Post by: bcooter on June 21, 2014, 03:56:49 pm

15 stops or 12 we've worked around this in the real world forever and a flat skinny 15 stop clip doesn't mean it's always useful. 

Back to the real world of usability.

This week, we were picking up some drives and filters for a production and though the A7s isn't on the shelf yet, I did some focusing comparisions with the A7r next to my gh3's and em-1, because the A7s and R use the same focus system, though I believe the S is suppose to be slightly improved.

Bottom line is the A7r autofocus minimully ok in video and stills, nothing spectacular or equal in stills to almost any ovf camera not even equal to the oly and panasonic.  The olympus em-1 on video tracking is actually pretty good, the gh3 just a step above them all in video autofocus, especially the touch screen focus.

Now, this is the 4th time I've briefly tried a Sony A series camera because in essence it's perfect for some of our productions, A 7r for stills a 7s for video, especially with it's high sensitivity would be a huge advantage in size and traveling.

Anyway, these small cameras given their price are amazing regardless of the things I'd like to see.   

I think we're a few generations or more off before we see it.

I do think given that the a7s allows real nightime photography without 2.5k hmi's and in sd goes to 120 fps it has a real place.

The thing that always throws me is If I pick up an A7 anything it feels ok, kind of a rushed to market camera, but when you directly use it next to the olympus and the panasonic the Sony feels like a lightweight mockup.

Maybe this is the way electronic cameras should be built.   Why make the camera built like a 10 year device, when they're gonna change it in 12 months?

Still, Sony is on to something is they just stick with this FE format. 

IMO

BC




Title: Re: A7s first impressions
Post by: Telecaster on June 21, 2014, 11:53:27 pm
The thing that always throws me is If I pick up an A7 anything it feels ok, kind of a rushed to market camera, but when you directly use it next to the olympus and the panasonic the Sony feels like a lightweight mockup.

Maybe this is the way electronic cameras should be built. Why make the camera built like a 10 year device, when they're gonna change it in 12 months?

Still, Sony is on to something is they just stick with this FE format. 

Yep. My prospective A7r buyer awhile back wussed out on the deal so I decided to keep it. The 35 & 55mm lenses are really nice. Once Sony/Zeiss comes out with its 28 & 85mm options (they're on the "roadmap") I'll consider it a complete system...for my wants/needs, that is. The camera does have a prototype-ish feel to it. As does the Blackmagic PCC, which kinda is a prototype, I guess.   :)  Might as well admit that most cameras are just commodity items now...shoot 'em & boot 'em.

-Dave-
Title: Re: A7s first impressions
Post by: barryfitzgerald on June 22, 2014, 08:37:30 am
Yep. My prospective A7r buyer awhile back wussed out on the deal so I decided to keep it. The 35 & 55mm lenses are really nice. Once Sony/Zeiss comes out with its 28 & 85mm options (they're on the "roadmap") I'll consider it a complete system...for my wants/needs, that is. The camera does have a prototype-ish feel to it. As does the Blackmagic PCC, which kinda is a prototype, I guess.   :)  Might as well admit that most cameras are just commodity items now...shoot 'em & boot 'em.

-Dave-

I've still got my 2005 era DSLR's a meagre 6mp but hey they work and take photos (and are worth very little on the s/h market thus not worth selling). Things have moved on tech wise, but back to basics erm well it's about taking pictures and they can still do that.
I am glad the debate isn't about purely megapixels (my little tests reveal very little real world difference 16 to 24mp) 12mp might well be sufficient for many people. On the other hand the discussion about DR would be better served with practical examples (ie photos you might take) Tech talk is fine..real stuff hits harder

Title: Re: A7s first impressions
Post by: bjanes on June 22, 2014, 03:53:51 pm
Correct, I forgot to add that.

There is however a benefit to sampling actual image sensels. The actual sensels being used for image capture may be affected by surrounding electronics (e.g. amplifier glow), and pattern noise. By only using a narrow strip of masked sensels on one side of the sensor array, we may get a somewhat biased (positive or negative) outlook. Also important is to determine if the row/column directly adjacent to the unmasked sensels is not affected by cross-talk or light leakage. It's sometimes better to not include that 1 pixel row/column of the multiple row/column masked area.

Cheers,
Bart


Bart,

Your assertion about the use of the masked pixels is well taken and some tests that I have done clarify that point. I had previously performed an analysis of my D800e sensor using your method of paired images. I used ImagesPlus as outlined by Roger Clark (http://www.clarkvision.com/articles/evaluation-1d2/). Since the D800e clips the readnoise in a dark frame, one must use an alternative method to determine the read noise. One solution is to plot the variance against the raw data number, using low exposures above the point where the read noise is clipped. The slope is the reciprocal of the gain, and the intercept is equal to the read noise squared. This is the method that Peter Facey used is his analysis (http://www.brisk.org.uk/photog/d3readn.html) of the D3.

The results of such a plot are shown below. The read noise is 1.07 ADUs and the gain is 3.24 e-/14 bit data number.

(http://bjanes.smugmug.com/Photography/Sensor-Analysis/D800eSensor/i-nQP5dsB/0/O/LowExpGraph.png)

Here are the masked pixels as viewed in Rawigger with the sensor near saturation.

(http://bjanes.smugmug.com/Photography/Sensor-Analysis/D800eSensor/i-jHnW5nc/0/O/RD_Img15_masked%20Pixels.png)

And the masked pixels for determination of read noise are selected in the image below.  The dark frame pixels have a value of approximately 1.5 DN, which is higher than the method derived from the plot.

(http://bjanes.smugmug.com/Photography/Sensor-Analysis/D800eSensor/i-c7gtJW6/0/O/RD_Img15_masked%20values.png)

These value of these masked pixels is affected by the saturation of the sensor as shown in the plot below. The x-axis is the pixel value of the unmasked pixels.

(http://bjanes.smugmug.com/Photography/Sensor-Analysis/D800eSensor/i-s9T39fX/0/O/MaskedPixelGraph.png)

Here are the Rawdigger values for the masked pixels in a lens cap exposure. The value is similar to that obtained with the interecept method.

(http://bjanes.smugmug.com/Photography/Sensor-Analysis/D800eSensor/i-sF5pKfr/0/O/RD_DarkFrameMasked.png)

The unanswered question is whether the read noise actually varies with sensor saturation or if the larger values of the masked pixels near sensor saturation is due to cross talk or other factors. There does not appear to be any blooming adjacent to the edge of the mask. What do you think?


Bill
Title: Re: A7s first impressions
Post by: jfirneno on June 22, 2014, 04:08:37 pm
Michael:
Very interesting article.  I know this thread is a few days old but if you are still following it I have a question.

I'm an A7R (and A850 and several other Sony cameras) user and am extremely interested in adding the A7S for indoor no-flash shooting.  Could you comment on whether the A7S seemed more capable of low light auto-focus than the other A7 cameras?

Thanks in advance,
John
Title: Re: A7s first impressions
Post by: bjanes on June 22, 2014, 04:13:47 pm
Bart,

Sony uses Engineering Dynamic Range. DxO uses 1:1 S/N. So, not directly comparable.

The important point, to my view, is not the absolute measured number under either schema, by rather the comparative numbers.

DxO now has S/N analysis for some 270 cameras of all brands. These are self consistent and done by one lab presumably using the same methodology.

On that basis the A7s simply is not what many people hoped it would be. That's really what the whole debate is about.

Michael


I think Michael is right here. The engineering definition of DR set the noise flow at the read noise without any signal (e.g. with the lens cap on the camera). A noise floor at the S:N of one does have a signal.

I performed some calculations for the Nikon D800e using a read noise of 1.04 ADUs, adding various amounts of signal. The shot noise is the square root of the signal and the total noise can be calculated by adding the shot noise in quadrature. DR is calculated by dividing the sensor saturation value of 15875 by the calculated noise.

(http://bjanes.smugmug.com/Photography/Sensor-Analysis/D800eSensor/i-NZXpQhL/0/O/SNR%20Calculations.png)

One value for the noise floor the DR is the Rose criterion. The Rose criterion (http://en.wikipedia.org/wiki/Signal-to-noise_ratio) (named after Albert Rose) states that an SNR of at least 5 is needed to be able to distinguish image features at 100% certainty. An SNR less than 5 means less than 100% certainty in identifying image details.

Figure 13 of Emil Martinec's post (http://theory.uchicago.edu/~ejm/pix/20d/tests/noise/noise-p2.html#SNR-DR) demonstrates an image with varioius SNRs. In that image a SNR of 4 does show the text in fair detail.

Bill
Title: Re: A7s first impressions
Post by: Telecaster on June 22, 2014, 04:26:44 pm
I've still got my 2005 era DSLR's a meagre 6mp but hey they work and take photos (and are worth very little on the s/h market thus not worth selling). Things have moved on tech wise, but back to basics erm well it's about taking pictures and they can still do that.

Yup. I still have my Epson R-D1, also a 6mp camera. It shoots above its mp weight. I no longer use it seriously, though, due to its high power draw and its batteries' declining ability to hold a charge. It's not quite in Leica territory build-wise but it's not that far off. Sony's A7-series cameras are extremely capable but are if anything lacking in heft and apparent solidity. IMO anyway...and I tend to prefer lighter-weight cameras. I have to wonder how they'll hold up to long-term pro-level use. In fact I don't think they're intended for that. Thus my "shoot 'em & boot 'em" comment...in a pro context anyway.

-Dave-
Title: Re: A7s first impressions
Post by: michael on June 22, 2014, 04:46:36 pm
Yes, by between one and 2.5 stops, depending on various factors. DxO shows the A7s to be among the lowest noise cameras on the market as high ISO.

But also take into account lenses. If you are using slower lenses right now, it might make sense to simply get a faster lens. All depends on what you're shooting, how big you print, your budget, etc.

Michael
Title: Re: A7s first impressions
Post by: jfirneno on June 22, 2014, 06:35:10 pm
Thanks Michael.  I'm renting one for a party at the end of next month.  I've been using the 35mm and 55mm FE lenses on the A7R plus some a-mount lenses like the 135/f1.8 adapted using the LAEA3.  ISO 6400 is all right, but if the A7S can give me 6400 that looks like 3200 on the A7R then I'll be all set.

Regards,
John