Sony A99...why make an SLR with an EVF?

Discussion in 'Other Systems' started by exakta, Jun 12, 2017.

  1. exakta

    exakta Mu-43 Veteran

    Jun 2, 2015
    I am totally confused here. It's like I have entered the twilight zone :hiding:

    I read that Sony's flagship A99 mkII DSLR has an OLED EVF. If there is no OVF, what does it need a mirror for and why is still considered an SLR?
  2. Witzgall

    Witzgall Mu-43 Rookie

    Sep 23, 2012
    The mirror is really just a beam/light splitter. It send some of the light to a dedicated phase detect focusing array. I have the camera, it really is quite amazing. I think of it as an advanced mirrorless camera, as technically, it is not a mirror, in the DSLR sense. So you get the best of mirrorless and a DSLR.
    • Agree Agree x 1
  3. vm666

    vm666 Mu-43 Veteran Subscribing Member

    Jan 19, 2013
    I suppose that Sony designed this to reuse the technology that they had in their previous DSLR, especially the AF sensor.

    Well... It is as bulky as any other 24x36 DSLR, and it has a long flange distance, so you cannot adapt legacy lenses (or just a few ones)
    How is the EVF by the way? On paper, it does not look much better than the old Sony A7 or the OM-D E-M5 Mark II.
  4. dwig

    dwig Mu-43 Top Veteran

    Jun 26, 2010
    Key West FL
    It is not really an SLR, at least by the classic definition. They like keeping the "DSLR", or "DSLR-like, moniker for sales appeal.

    They chosen to build a camera that acts like a standard mirrorless camera in almost all respects, other than focusing, for the many associated benefits while also using the faster phase-detection AF classically used in DSLRs, which requires the mirror to pass light to the AF system.

    Using a beamsplitter has its downsides though. One, you are shooting through the beamsplitter and there will be some optical loss. Two, less light is passed to the image sensor than in a regular DSLR or mirrorless. This will have a modest impact on low light performance.
  5. Biro

    Biro Mu-43 All-Pro

    May 8, 2011
    Jersey Shore
    Why ask why? Follow the money. Ultimately, EVF's will become standard across all camera ranges with very few exceptions... because they're much cheaper to engineer and build. They'll eventually be good enough for everyone... and are good enough for many already.

    Sony's A-series SLT cameras have been on the market for a number of years now. But the company knew EVF's would be the future when they designed the first one. This was a way of bringing the technology to those with A-mount lenses without the need for an adaptor.

    But we should view the SLT series as an interim measure. Sony's emphasis on the A7 mirrorless full-frame series and FE mount makes that clear.
    Last edited: Jun 13, 2017
  6. eteless

    eteless Mu-43 All-Pro

    Jun 20, 2014
    There are some mitigating factors (some might say advantages) which muddy the water even more;
    + As the phase detect sensor isn't part of the sensor fabrication it's possible (and everyone does it) to use much larger photosites than the pixels on the image sensor - so you could (in theory) get more reliable AF at lower light levels.
    + The larger photosites will improve autofocus at higher light levels as a much faster readout speed can be used (higher readout speeds get convoluted quickly using image sensor AF as you need to balance higher speed AF readouts (of a small portion of the sensor) with the need for full sensor readouts to update the EVF).
    + As the readout of PD isn't tied to the sensor you can do readouts during exposure or during readout of the image sensor after taking a picture, this means there's no need for a delay between pictures to check focus before another picture is taken (although one electronic readout is useful to update the EVF) - thus higher a potential for higher framerates exists.

    Personally I find the trade offs compelling when contrasted against a DSLR, IMO we have long passed the point where noise is a massively limiting factor and ease/enjoyment of use (ergonomics / autofocus performance / viewfinder (and in the case of m4/3, size/weight)) generally have a higher priority when I'm looking for equipment.
  7. exakta

    exakta Mu-43 Veteran

    Jun 2, 2015
    Interesting, it seems that the only real advantage is in the focusing?

    The idea of semi-transparent mirrors is not new, the old Canon Pellix of the mid 1960s had one, so there was no finder blackout and no mirror slap vibration. The TTL spot meter flipped up in front of the shutter! The light loss both in the finder (1.5 stops) and on film (0.5 stop) was a drawback, any dirt or dust on the mirror would affect the exposure.

    Canon later offered a special version of the F1 with a pellicle mirror (but not the flip-up meter cell) for motor drive users.


    How much light loss does the SLT mirror cause?
  8. vm666

    vm666 Mu-43 Veteran Subscribing Member

    Jan 19, 2013
    Odd, isn't it? They could have kept a SLR viewfinder.

    The Olympus E-10 used one too.
    IIRC, 2/3 of the light went to the sensor, and 1/3 to the viewfinder.
  9. tkbslc

    tkbslc Mu-43 Legend

    Wait, I thought those of us who shot mirrorless thought that EVF was the future. Now we are arguing in favor of an OVF?

    EVF means a bigger viewfinder with real overlays and exposure preview. Same benefits you get with mirrorless, only they use the mirror for traditional phase AF for use with their existing mount.
  10. vm666

    vm666 Mu-43 Veteran Subscribing Member

    Jan 19, 2013
    Well, DSLR fans do not like EVFs so I suspect that the market for this camera is restricted.
    And sincerely, even if I love my 2.4 Mp EVFs (Sony A7, OM-D E-M1...), I have to admit that they are not as fine as a clear focusing screen. In very low light, I prefer the EVF but in daylight, 24x36 DSLR OVF are really good (I don't like APS-C OVF much because they are too small)

    I have the impression that we have the worse of both worlds here. The camera is as bulky as a DSLR, MILC are smaller.
    Last but not least, according to miscellaneous reviews, its AF is not that good.

    it seems that Sony cannot build a A7 that is fully compatible with Sony A / Minolta lenses, so they keep the SLT line.
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