Mark Weir talks about SLT technology and Sony SLT A58


Sony’s New SLT Camera, A-58, will appear in major electronic stores early next week. To learn more about SLT cameras and specifically A-58 and how it could help the filmmakers, we interviewed Mark Weir, Senior Manager of Technology for Sony Electronics Digital Imaging.

We will follow this interview with a Sony SLT A58 review and soon with a series of reviews using Sony SLT A99.

Bijan Tehrani: Please tell us a little bit about the SLT technology and how it is different from the traditional SLR technology.
Mark Weir: Traditional SLR technology, at least when it regards the mirror, has been the same since the introduction of SLR in the 40s and 50s. The mirror is down during composition for framing, and at the moment of exposure, the mirror lifts, the shutter blades open, the viewfinder goes dark and the picture is taken. Obviously, SLRs were created long before the idea of capturing video. Digital SLRs appeared in the 90s and became very popular in the last decade but realistically, the mechanism of the mirror remained unchanged from the days of film SLRs.

So, in 2010, SONY proposed a new idea, that is to use a semi-transparent mirror, which we refer to loosely as “the translucent mirror”, to realize a fixed mirror that does not move at the moment of exposure. In so doing, we allow the camera to do two different operations simultaneously and that is the secret of its benefit. Because the mirror does not move, the viewfinder remains functional even during recording, and the auto-focus system remains functional even during recording. This is very important for still photography but it’s much more important for video because … optical viewfinder cameras essentially become mirror-less cameras when they capture video – that is to say the mirror lifts and remains lifted during recording and only the live view on the LCD is available for framing while the eye-level viewfinder is disabled.

The primary focusing system of an SLR, which is its phase detection AF system, is also disabled when recording video because the mirror is lifted. Up until recently, SLRs couldn’t auto-focus at all when capturing video but in the last couple of years, an effort to provide contrast AF has been made but it’s very slow and has great difficulty tracking moving subjects with auto-focus.

With the translucent mirror technology in Sony cameras, the mirror being stable by design, the camera AF system remains fully functional during video capture, as well as the camera’s electronic viewfinder. That makes for a very different shooting experience.

BT: As far as the quality of photos and still pictures, is there any difference in the precise capture?
MW: No. SLT technology is not the first to use a semi-transparent mirror. Semi-transparent mirrors were developed and used during the days of SLR without any concern for image quality. Generally speaking, although we don’t release a specification for it, about a third of a stop of light transmission is lost with the translucent mirror because some of the light is being deflected upwards the AF sensor. But in terms of image quality itself, Sony’s translucent mirror cameras have been tested far and wide, and the general impression is that there is no loss of image quality.

BT: One thing my first test shows is that during video – and most readers will be interested in capturing video and film, especially with the entry level A-58 which is a great tool for students and young filmmakers – is that you hardly see any problems with Sony of focusing when you are shooting video. Especially for documentary filmmakers or filmmakers who use new methods of film making such as continuous hand-held shots, this shows a great improvement over the SLR, which is almost impossible to use for that. What has been the reaction to video quality, especially the focusing system, of SLT system?
MW: It’s been quite good. When evaluating digital SLRs, there are many different parameters. When people consider video performance specifically, the translucent mirror cameras are being credited by the general public and the press as being a much different and much better user experience with greater usability than digital SLRs, simply because of their advantages in terms of auto-focus, tracking focus – which is something contrast AF can’t do to begin with – as well as the ability to use the EVF while shooting. These differences have gotten them a lot of positive recognition when it comes to shooting video with an SLR.

BT: What is the idea behind presenting the A-58 on the market? We here very much loved it and would recommend it to student filmmakers and filmmakers who want an entry-level camera.
MW: The A-58 is really our third-generation of offering SLT cameras. One of the roles of the A-58 is to provide the performance that SLTs can deliver at a much more affordable level than ever. We’ve been able to make SLT cameras close to this kind of price in the past – around $599 to $699 – but we’ve never been able to provide a feature-rich camera like the A-58 at $599 before. So it replaces two models in our line, one that was $599 and one that was $799, but with the look and feel and feature set of much more expensive cameras.

The primary reason for that is that there’s been a significant growth in the very affordable SLRs: the more affordable $499 and $599 are attracting a new class of users who would not have been able to afford an SLR in the past. As there is more and more interest in imaging overall, interest in a better quality has emerged. So what we’ve done with the A-58 is put together a package of advantages within reach of more mainstream consumers.

We’ve relied on the translucent mirror technology to give the A58 video-capture experience that’s much easier and more enjoyable for a new user. Most people are becoming aware that the user video experience for an SLR user is a bit challenging compared to say, a camcorder. If you’re prepared to pull focus, if you’re prepared to make manual adjustments or invest time and effort to get the SLR to perform well in video, no problem, but for mainstream users who are looking for SLR as a solution for better photography, they expect that the video experience will be at least as good as a camcorder or better, and they’re finding that with most SLR cameras, the experience is anything but.

BT: My experience as someone who has some experience in film making, having worked where it was necessary to have an extra person in charge of focus, this focus feature is an amazing difference. My next question is about lenses. Canon or Nikon offer so many different lenses for their cameras. Is it the same with Sony?
MW: To be Frank, the number of lenses is not as large as the number of lenses in the Nikon or Canon system, which offers about 60. We offer 32. However, several of the lenses in Canon or Nikon are identical but one offers image stabilization and the other doesn’t, at least a dozen, so they are essentially variants, so it makes the count a little closer. In my experience, every lens system has its pluses and minuses. Certainly, there are some very exclusive lenses that our competitors offer that we do not but we also offer some lenses that are very exclusive to us. For instance, the Sony A-mount system is the only system that offers the Carl Zeiss auto focus lenses. Carl Zeiss lenses are available on other mounts but not with auto-focus. We think that that is a profound advantage for us.

We also offer two lines of premium lenses. Besides the Carl Zeiss lenses, we have our G series lenses, which are descended from a Minolta heritage, several of which are truly legendary lenses. Long before we were in the SLR business, Minolta was already making some very legendary lenses; we maintained that heritage and some of those models have migrated into our system. Although Canon offer L-glass and Nikon offers exclusive lenses as well, by offering the Carl Zeiss, the G series, as well as the Alpha lenses, we really offer some very excellent choices.
Even beyond the lenses, there’s another fundamental part of the system that really helps the user get that much more out of lenses, and that is in-camera image stabilization as opposed to image stabilization in a lens. We think of this as a big advantage, particularly in the context of video but also for still.

There are some lenses in which image stabilization is not available in any system, except for ours. If you take a look at standard focal length or portrait-focal length – wide aperture lenses, no one has yet developed image stabilization. For instance, a 50mm F1-4, a 35mm F1-4, a 24-70 F2.8: no one offers image stabilization for those lenses. Neither do we, but our camera itself provides image stabilization, so indirectly, our system provides image stabilization to all the lenses that is not available in our competitors systems.

BT: Something that excited me was that the lenses SONY SLT uses are Carl Zeiss and Minolta. My experience with Minolta lenses had been amazing, so I think two of the top lenses of the world are being used by Sony. If people are working on more serious projects, and they may need 10-80s, 60Ps and 80-P-60 and want to shoot with that quality or in general better quality in the video, what does SONY offer in a system like A-99?
MW: The A-99 offers one significant advantages which are not included in the more mainstream models like the A-58. We’re finding that the ability to shoot at 60p video and then convert down to 24p in post allows for a 2.5 factor in slow-motion, which many videographers really enjoy, not only in cameras like the A-99, but certainly in professional cameras like the FS-700 with its higher frame rate as well. We’re really exploring a world of slow-motion, which is something a lot of videograhers put a lot of emphasis on. 60p is a great advantage in A-99.

Another advantage is to output clean, uncompressed HDMI. We’ve been able to record outputs as high as 250 MB per sec on HDMI, and the outboard recorders which can handle 60p are just becoming available now. Patimus introduced Ninja 2, and it can record 60P out of the HDMI. That’s a really big advantage.

You can free yourself of the in-camera codec, you can record and work in pro res if you like. The ability to get uncompressed out of the camera and work with it in post is a real advantage.
Another factor we put in the A-99, in particular it regards video production, is the ability to use XLR microphones with an audio-kit that we sell separately. Rather than just being an outboard XLR breakout box, which plugs into the camera through a standard unbalanced mini jack, we put terminals in the camera that will allow it to take unbalanced input right into the record pre-amps of the camera. That’s a versatility that we think is a great advantage: not only will you get great video but also sound.

We also put in adjustable input levels, which are included on the camera a silent rotary controller that can be configured for a variety of different controls, such that adjustments can be made without noise pick-up. So there’s a lot of functionality that we put in the A-99, particularly around video capture.

BT: We had a meeting today before we came up with our questions and one of our tech guys heard that there are new added auto-focus added in the A-58 that may not exist in the A-99. Is this correct?
MW: We’ve advanced the tracking AF capability with the A-58. Typically manufacturers will update their camera system every year. The A-58 is no exception. It includes some functionality that we’ve developed for the 2013 year which hadn’t existed on our previous models. We have a technology called lock-on AF which works with the object recognition system of the camera as well as the AF system so that the camera can recognize an object and direct the AF system to lock onto it. That’s a capability that even the A-99 does not include. And that’s particularly useful if you have objects in the scene that are moving unpredictably. Keep in mind that the A-99 has some benefits of its own which are realized by no other camera including the A-58.

The A-99 has what we call the world’s first and at least for now the world’s only dual phase detect AF system. It uses not only phase detect points on a conventional phase detect point AF sensor like every other SLR, but it also includes phase detect AF point on the image sensor itself. The sensor has embedded on its surface 102 phase detect AF point, which creates a very dense field of AF points in the scene. Therefore, there is much more information available to the AF processor. For instance, when the subject moves across the scene, there are a total of 121 points of AF detection that can follow it, therefore increasing the likelihood of keeping focus on the subject as he moves across the plane. The AF system is not only detecting the subject moving across the plane of focus, it’s also keeping an eye on the parameter of depth. It’s really the only SLR that can do that because it’s the only SLR that’s collecting phase AF information from a dedicated sensor as well as from the image sensor itself.

There is also a control which is particularly handy in the A-99, which allows you to determine the reaction rate of the AF system to subjects that may be moving across the frame. You can set the camera to react very fast to those things that might move across the frame and you can also set it to react very slowly. So it is true that the A-58 does have a little bit of technology that we developed for this year but the overwhelming preponderance of the AF capabilities probably still have to go to the A-99.

BT: How do you see future developments in this field?
MW: We are rather restricted, in Sony, of our authority to comment on the future but if you look at our professional video offerings, obviously we’re very well-known in the world of professional video acquisition, not only in the world of digital cinema, with our Cine Alta cameras, but also in the world of broadcast production and ENG, where we’ve been known for decades. And if you take the news out of this week’s NAB show, you can see that SONY made some pretty strong introductions and comments about the value of 4K video production. Our newly released F-5 and F-55 Cine Alta cameras have been very used in the film making community and the F 65 has been well known for its use on many feature motion pictures and television shows. SO I think 4K is going to figure prominently in the world of video acquisition in the coming years.

That said I think 2K is still very powerful. I think the world of interchangeable lens video cameras as opposed to interchangeable DSLRs is certainly going to develop. We of course have video capture in our SLRs but we also have interchangeable lens video cameras, with large image sensors that we introduced as far back as 2010 and we have a fully developed line of those as well.

So I think if you look at the world of creative videography, where enthusiasts as well as mainstream consumers are starting to crave better quality video capture, I would say that there is a lot happening in the industry and this will continue moving forward. It’s a pretty exciting time!


About Author

Bijan Tehrani

Bijan Tehrani a film director, film critic and writer, works as editor in chief of Cinema Without Borders while teaching Language of Film and Film History at workshops nationwide. Bijan has won several awards in international film festivals and book fairs for his short films and children's books.

Leave A Reply