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back to article Sony focuses on full-frame snappers with tasty tech

Sony snapped into action today with a wide range of camera launches including a fresh NEX, a snazzy full-frame compact and apparently the world's first full-frame SLT with a dual AF system. The latest NEX-6 mirrorless compact camera system features a 16.1Mp Exmor APS HD Cmos sensor, with ISO sensitivity of up to 25600. The …

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Anonymous Coward

Is it still green?

A friend used a Sony DSLR as a semi-pro until repeated comments led him to go Nikon and then on comparing pictures he found that the Sony had a gree hue to the shots. He's sticking with the Nikon for the pro work.

Don't look at me, I shoot Pentax ... and if I could get hold of them face to face, I probably would ... shoot ... Pentax.

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Re: Is it still green?

Don't think this is a general Sony problem. I have been with Sony DSLRs since they launched (to reuse my Minolta lenses), and haven't noticed any green evilness.

Build quality wasn't their strong point to start with, but it has improved.

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Anonymous Coward

Re: Is it still green?

Given Nikon used Sony sensors for years and probably do on some models I suspect that's down to processing or paranoia?

It's Fuji film all over again.

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Silver badge

SLT?

Does this not mean that the amounts of light reaching both the viewfinder and the sensor is cut roughly in half? In dim light, this would be a drawback. Though we do not need a bright viewfinder to focus any more, framing an image nicely in dim light might be a problem. Less light hitting the sensor lower the signal-to-noise ratio.

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Boffin

Re: SLT?

No. About 30% (half a stop) is reflected up to the AF phase-detect sensors. The rest goes to the main sensor. The main sensor is read continuously for the electronic viewfinder (just like a compact). This does mean a slight reduction in high-ISO performance, so noise at ISO 1600 would be the same as noise at about ISO 2400 on a non-SLT camera (like the Sony NEX, and Nikon, Pentax cameras that use the same Sony sensors. The benefits for most people (full-time AF, WYSIWYG viewfinder) outweigh that small increase in noise, but it depends what you shoot. Also some people don't like the EVF, either because they're hyper-sensitive to flicker, or the 1/50th second update lag is critical. I have a first gen SLT (Sony A55) and think it's great. YMMV.

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Thumb Up

Re: SLT?

You lose about 1/2 an F-stop of light, allegedly. I've not noticed as it's low light performance is also excellent. And in answer to the previous post, I've not noticed any greeness either.

Was a bit nervous about moving away from a standard SLR, but I bought the SLT-A57 and it's the best digital camera I've used - previously had the Pentax Kr and have used mid range Canon's and Nikons.

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@Antony Jones

Do you get a weird optical effect when you blink looking through the electronic viewfinder on the A55?

When I do, the overlaid exposure data, histogram and artificial horizon momentarily appear to break down into their RGB colour components, each component slightly displaced laterally or vertically from each other.

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Re: @Antony Jones

The A55 uses a sequential display so the LCD is one colour with an alternating red/green/blue LED. So yes, if you blink or move the camera too quickly you'll get some false colour effects. I've just grown to ignore it, but when picking up the camera after not using it for a while it is noticeable. It's the same as with DLP projectors that use a colour wheel. Some people are really sensitive to it, but most don't notice.

The latest high-end models (like the A99) use OLEDs, so don't have this issue.

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Anonymous Coward

A99 AF

What's with those AF points on the A99? 19 cross-type, plus 102 phase-detect AF points? Firstly, I always though cross-type sensors were a type of phase-detect sensor, based on having two phase detect strips arranged in a cross. I suppose contrast-detect is cross type by default, since it's based on the orthogonal grid of the main sensor.

Looking at the press release (where that piece of text originally came from) the 102 point phase-detect points are on-sensor, which doesn't make any sense to me. Phase-detect systems rely on splitting parts of the light from different routes through the lens, checking for any phase difference from the two areas that would indicate the lens isn't focussed. The sensor gets light from all routes through the sensor, to maximise the light it can collect. It would also suggest the 19 cross-type sensors aren't on sensor, as I'd originally assumed they might be (if they were in fact contrast-detect type).

I really can't make head nor tail of this. Mind you, Sony's semi-transparent technology stuff confuses me at the best of times.

What am I missing? And where's the contrast-detect in this setup?

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Boffin

Re: A99 AF

Here's Sony's patent on the method

If I understand it right, the extra phase detector pixels are arranged so that there is a microlens, a little 'well' below, and at the bottom of the 'well' are two pixels that meet at the middle. Light along one path from one side of the camera lens exit pupil hits one pixel while light along the path from the other side hits the other pixel. Phase detection is done from strips of these 'half-and-half' pixels.

The main 19 cross-type sensors are on the sensor array, separate from the main imaging array (otherwise the camera wouldn't need the semi-transparent mirror).

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Anonymous Coward

Re: A99 AF

Ah, that would make sense. I suppose this wording from the press release could be ambiguous:

"This camera’s main focusing system – a 19-point AF system with 11 cross sensors - is complemented by a 102-point focal plane phase-detection AF sensor overlaying the main image sensor."

The way I read that suggest it's saying the 102 sensor elements are overlaid with the sensor, while the 19 elements are therefore in the more usual position, but it makes more sense if the 19 elements are in the sensor, as fitting too many in there would no doubt be problematic, while having only 19 conventional phase-detect elements in a top-of-the-range camera would be a little low.

It seems I misread the article, and it's not claiming the A99 features any contrast-detect focussing (which is a shame, given how accurate and reliable contrast-detect AF is). It'll be interesting to see how this dual-phase-detect AF system works in the wild.

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