Q&A with the SLT Development Team

[KevinBarrett]

I recently had the opportunity to pose some questions to the SLT development team through a representative from Sony. This was some weeks ago when the cameras were still quite new and mysterious, but the answers have only just got back to me and I've been given permission to share them. There may or may not be new or pertinent information here about the cameras, however, there is some interesting information about decisions made in the development process.

The first five questions in this post were my own, after which the invitation was extended to other members of a small and varied community. More questions and answers follow in my next post. I apologize if some of the questions seem silly or repetitive, but they were posed by several different people over the course of a few days. Still, the development team was patient and understanding, and gave new and consistent answers for redundant questions.

Why was a bottom-hinged LCD design chosen for these cameras, rather than the more popular side-hinge?
Although there are some cameras that articulate the LCD with a hinge on the side, we chose the bottom hinge to keep the LCD in line with the optical axis of the lens. It also helps maintain a more compact body, and properly support the large, 3” LCD.


Are the sensitivity (ISO) settings calibrated so that they account for the light-loss from the transparent mirror? (That is to say, if the a55 and a580 each took a picture at ISO 400, f/5.6, 1/30 sec, would they be the same exposure?)
Only a very small amount of light is directed to the AF sensor by the Translucent Mirror. However, the sensitivity is calibrated so that equivalent exposure values are realized.


I noticed that the mirror flip-up operation (for cleaning) is accomplished manually--can the camera record an exposure in this state?
The shutter can be released with the mirror raised; however, a lens cannot be attached in the mirror up position as the translucent mirror is larger than a traditional instant-return mirror. Hope this helps clarify.


Were there any technological roadblocks that make it an impossibility to use manual exposure control for video in these new cameras?
It’s not impossible to include Manual Exposure control for video, however we chose not to include it in these models because of some basic limitations to Aperture and Shutter speed adjustment when any camera is recording video. Specifically, there is a limit to the range of shutter speeds that are appropriate for 30P capture – practically, it can’t be much longer than 1/60 sec or much shorter than 1/250 – so we chose not to include Shutter priority. There’s much more creative freedom in Aperture Priority, which the cameras do provide. However, Phase Detect AF has certain minimum aperture requirements (typically f/5.6), so Aperture Priority defaults to Manual AF to allow a wide range of aperture adjustment.


Will auto-exposure work with third-party, "unchipped" lenses? What about video capture or the other features, such as Sweep Panorama and Auto HDR?
Hi Everyone, I am still working on getting this one answered for you. Thanks for your patience.


I would like to know what the light loss is. A full stop (half the light)? 2/3 stop (1/3 the light)? 1/2 stop (1/4 the light)?
This is a question we often get asked but it is not information we disclose publicly.


From what I understand the a55 can't maintain live view in 10 fps mode but what about the EVF then, can you still track whatever you shoot through the EVF?
To support the a55’s 10fps continuous shooting, we rely on a rapid display of the most recently captured image rather than trying to create a Live preview. Some have suggested that this limits the ability to track fast action, but it actually works very well and makes a lot of sense. As for Live View operation, It would be very difficult to change the Image Sensor from capture to Live View display at 10 times/sec with current devices. If we consider optical preview, the handful of pro-level DSLRs that can reach 10fps have to cope with mirror black-out – the time during which the scene view is interrupted by the moving mirror and image capture. Even the shortest black-out time significantly reduces the view of the scene, so we think rapid display of captured images is a novel and quite workable solution.


50 seconds wait time between bursts will not be functional for my type of sport shooting. Is that only when the buffer is completely full?
Slow cards combined with lots of shots will create long writing times but we have shot with Class 10 SD card and were always able to continue shooting (at a reduced rate). The camera never locked up while clearing its buffer and could continue shooting. It’s true that it takes a long time to for the writing activity to finish, but nearly 40 16MP frames at 10fps is a lot of data! Hope this info is helpful.

[KevinBarrett]

From various sources, it seems that videos can only be done at full aperture. I understand that AF with phase detection like in the SLT requires the aperture to be at least F6.3 or something in that area. So the question is: is this true? When using a 85/1.4 (just an example) you can only use it at F1.4 in video mode with AF? If that's so, why not allowing the F value to be picked by the user between 1.4 and 6.3 (or say F4 or F5.6 may be)?
That's a fair question however in this camera, there's always an aperture priority option (though in manual focus). Because phase detect AF relies on a fairly wide max aperture (in all DSLRs), these cameras’ exposure control system defaults to the lens’ max aperture during video recording with AF. We understand that this might be a challenge when using very wide aperture lenses under very bright conditions, but the typical use of these models will be variable aperture zoom lenses.


I have seen some videos made with A55, and the AF is impressive when changing focus point. But I have to admit it may be too fast if you want a slow and smooth transition between the subject and the background for example. Anything can be done in that area (besides using MF I guess)?
The responsiveness of Phase Defect AF is extremely fast but unfortunately, there's no way to regulate the responsiveness of the phase defect AF in-movie, it will always be quick. But like you mentioned, a good work around for this is that we recommend manual focus to give you total control of the artistic effect.


In addition to the 15 AF points, has anything more fundamental about the AF system been changed? ... as in, does it work at smaller apertures?
Phase detect AF systems always work at max aperture (largest iris opening, smallest F #) in still photography. The lens aperture is always open all the way until the moment of exposure so AF system is always using the widest aperture. The new AF sensor uses f/5.6 line sensors (15 of them actually, three of which are cross-type) which provide a nice range for this priced camera however it does not have the higher precision f/2.8 line sensors found in enthusiast class cameras such as the a700/a850/a900.


What I am really very worried about is that the A580 has not been introduced in the US and is not listed on SonyStyle USA. Why? Can we expect a later introduction of this model in the US?
Actually, although it was not included in the initial announcements, we have decided to introduce DSLR-a580 in the US. It will reach stores in early November, and be available in body only (a580) and a bundle with SAL1855 lens (a580L).


The A33 & A55 use the same batteries as the NEX-3 & NEX-5.The 14MP A33 can create 270 images in 'Live View' and 340 with the viewfinder, on a single battery.The 14MP A560 can create 560 images in 'Live View' and 1050 with the viewfinder, on a single battery.According to the Sony A550 Instruction Manual (Like the A33 and A560, the A550 also creates 14MP images.), 319 Large Fine JPEG images take up about 2GB.Therefore, an A33 will require 2 fully charged batteries to fill a 4GB SDHC Card. And there's no vertical grip/battery pack for it. That's pretty bad for a camera that's supposed to be able to take photos at the rate of 7 per second! THAT'S LESS THAN 40 SECONDS OF SHOOTING TIME ON A SINGLE BATTERY!And the 16MP A55 is worse! (There's no word yet about how much video you can record before the battery runs out.)On the other hand, the A560 can almost fill a 4GB card on a single battery, when using 'Live View', and can create more than 6.5GB of images when using the viewfinder. And there's a vertical grip/battery pack for it! Why was this done this way?
In this case it’s definitely an apples and oranges thing. For some, battery life to the above extent is a priority and for that need, larger bodied DSLRs are our recommended choice as bigger cameras can often accommodate larger batteries/more batteries resulting in longer battery life. We offer a variety of cameras which meet this battery need and can recommend some models for you based on the need. These cameras were designed to be light and compact. In that case, having a vertical grip which can accommodate an additional battery or incorporate a larger battery would have created a larger camera body which would be heavier in weight which wasn't the intent of this design.


Why is there no option for manual control?
Both cameras have an option of manual control.


Why is AVCHD set at 1080i (interlaced wrapper)? Thats low 17Mbit (same as SONY's compacts)
The sensor outputs 30P and the data is recorded in 1920x1080 60i so as to be compatible with the AVCHD codec. However, 30P recording in MP4 is available as well. The max data rate of 24Mbps (theoretical limit of AVCHD) is not offered, as these models are primarily still cameras.


Why does the NTSC version records in 30p off the sensor and gets put into interlaced wrapper?, and Why not allow PAL to capture for the Cine standard at 24p?
I’m still working on getting this one answered for ya. Thanks for your patience.


Why does the ultra fast phase detect AF only works in video mode when the aperture is wide open?
Phase detect AF relies on a certain minimum aperture from the lens. If you consider still photography, the lens is always at max aperture until the moment of exposure, and AF is always set while the lens is at max aperture. The same is true for video – the AF system depends on the lens aperture being at least f/5.6. Although there are several lenses of wide max (or constant) aperture, mainstream zoom lenses are almost always variable aperture, and max aperture can fall to f/5.6 when they are set to telephoto. Although it may not be the best solution for wide aperture lenses, AF in movie recording defaults to max aperture to insure high performance with a wide variety of lenses.


Why the limit to 1080/25p MP4 on the PAL camera (30p on NTSC models) is 1440x1080 and just 12Mbit?
Our focus with these models was to provide the best quality Full HD video playback on HDTVs (with AVCHD codec) while maintaining good versatility with MP4 for web applications. We realize that some users would appreciate even more versatility (higher bit rates, variable frame rates, etc) for professional applications, but this requires system resources which are beyond the design intentions for these models. We are aware of the demand for greater versatility and thanks for sharing the feedback.


Is there a means or plans for the Vertical Grip that could accommodate an extra battery and possibly allow the use of Compact Flash Cards?This could address several issues. Lack of proper power, faster media storage, provide more protection to the swerving 3 inch display.
It's good feedback. Similar to TCav's question, these specific cameras were designed to be light and compact. In that case, having a vertical grip which can accommodate an additional battery or incorporate a larger battery would have created a larger camera body which would be heavier in weight which wasn't the intent of this design. Again, great feedback and hopefully this info provided some context around these models.


Was it ever a consideration to reverse the way the transparent mirror works, so that the main sensor sees a reflection and the AF sensor sees what light passes through? It seems to me that this would minimize any distortions in the exposure that might have been introduced by the light passing through an extra pane of glass.
Reflection has some limitations of its own, but always good feedback.

[David Kilpatrick]

Krevin, I believe that with lenses faster than f/3.5, the camera sets the aperture to a fixed f/3.5, and for those which are slower it uses full aperture. It does not force f/1.4 as the exposure system can not cope with f/1.4 in full sunshine.

David

[Birma]

Hi Kevin - useful insight and "from the horses mouth" . Thanks for sharing these details.

[dynax800si]

Thanks Kevin, very interesting info.

[bfitzgerald]

"This is a question we often get asked but it is not information we disclose publicly"

Sigh....lol

Apart from that it was a decent stab at getting some answers from them.

[alphaomega]

Very interesting and thanks for going to the trouble. I got an answer to a question I had, namely how Sony handled the loss of light to the main sensor. They simply adjusted the ISO slightly up so that you get the same reading as with the A580. The more I read the closer I move towards the A580 next year unless a spectacular replacement for the A700 makes an appearance within the next 8-10 months. Interesting rebuttals to those who expect a £500 replacement for equipment normally costing thousands of pounds. Camera designed small so cannot fit large battery. Cannot add video normally costing big money in a cheap small model. Fit a faster card if you have buffer problems and be satisfied with what it can do within the spec. and money etc. Having spent my working life in engineering it all rings true. You settle on a spec. fitting a cost/sales profile and do your best, but as DPReview said do not expect 1D IV follow focus performance in the A55 costing many times less. Should be posted on DPReview if not already done. Would be good reading for all the Sony "critics" expecting gold for the cost of iron.

[Edgars L]

I think lot of people have question: how to clean mirror?

"Buy a larger body" is stupid suggestion because Sony didn't offer larger body with 10fps, phase AF during video and stills. Also faster card for reasonable price isn't available.

[aster]

Thank you for going to all the trouble, Kevin.

These answers shed some light indeed.

Yildiz

[Dusty]

"Buy a larger body" is stupid suggestion because Sony didn't offer larger body with 10fps, phase AF during video and stills. Also faster card for reasonable price isn't available.

This is the problem with a compromise system. People want a perfect and fast framerate DSLR with perfect video for $500, and they don't want to buy more expensive media to take advantage of it's capabilities.

If you can find it elsewhere for $500, and it will do 10fps on a cheap, s-l-o-w card, then don't look at the Sony.

Geesh! Sony has done it "like no other" and everyone is complaining. Wait 10 years and you may get your wish!

Kevin, thanks for all the info. How did you get to go to this?

Dusty

[KevinBarrett]

I'm glad we were able to get some interesting information back from the Sony guys, and I'm glad you all appreciated it. They were more friendly and unfiltered in their responses than I ever would have imagined. How did I get to do this? I maintained contact with a Sony blog editor from the old Backstage 101 site which was closed last spring.

[bfitzgerald]

If you can find it elsewhere for $500, and it will do 10fps on a cheap, s-l-o-w card, then don't look at the Sony.
Dusty

Who asked for 10fps? Really have no need for such a camera at all. This fps obsession with Sony comes with compromise in other areas. Nikon have a real semi pro £1000 body that does 6fps guess what's going to sell more?

FPS isn't interesting at all for my type of shots. I don't mind a bit more but have no need at all for 10fps.
I don't think folks were asking for that myself..just Sony thought it was a good idea that's all. Time will tell if it is.

[Dr. Harout]

Kevin, you've been quoted on SAR.

[KevinBarrett]

Barry, look at it this way: they made a camera that can do 6fps, maintaining live-view and all other expected functionality. Then they said, "well, what would it take to go faster, still?" I don't think the compromises to get it to 10 fps are ideal, but considering the price, it would be confounding for the SLT cameras to be slower than the NEX cameras, or the Cybershots, for that matter. Now that the processing power is there to handle huge files with such speed, it is disadvantageous to exclude it from cameras that aren't otherwise mechanically limited.

[BrianSmith]

I'm glad we were able to get some interesting information back from the Sony guys, and I'm glad you all appreciated it. They were more friendly and unfiltered in their responses than I ever would have imagined.

That has always been my experience with Sony. I'm glad you were able to see this for yourself. Nice Q&A Kevin!