Gary’s Parries 19/11/06

November 19, 2006 | Mark Goldstein | Gary's Parries | 0 Comments |

Gary's ParriesThis week’s Gary’s Parries topics are:

1. DSLR With Live View Movie Mode?

Introducing this week’s Gary’s Parries column. Everything you always wanted to know about digital cameras, but were afraid to ask. No question too difficult, or too easy. As a Senior Principal Software Engineer, and a former Assistant Professor of Computer Information Systems, as well as a recording studio owner/operator, inventor, and now, a digital camera enthusiast, GARY has more digital camera knowledge in his entire brain than most people have in their little finger. In the unlikely event that GARY would not know the answer to your question, he will answer it anyway, true to the spirit of the word “Parries”, a fencing term which, in this context, implies “cleverly evasive answers”. So let your imagination run wild. Email all your nagging digital camera questions to: garysparries@photographyblog.com , and then, En Garde!

You may also attach to your email an ORIGINAL PHOTO of your choosing. A preview of the photo will be displayed with your question, and a full-sized version will be just a click away. No personal information will be published with your question unless you specifically include it in the text or attached photo of your email, which may be further edited for grammar, content, or other reasons.

***
*** QUESTION 1—- DSLR WITH LIVE VIEW MOVIE MODE?
***

Dear Mr. Gary,

With good video capability becoming an increasingly important feature in digicams, and that being one of the reasons why some prosumers would stay away from a DSLR, why do DSLR manufacturers not devise a means of keeping the SLR mirror up (as in stuck to the top of the mirror box) whenever the camera is in movie mode? Surely, large APS sensors are capable of capturing video, the proof of that being the Sigma DP1 high-end compact digital camera, which I assume can handle video like most other compacts.

I also hope that Panasonic and Sony soon equip their digicams with their revolutionary AVCHD compression technology that uses H.264 compression to store video on flash memory cards and mini-DVDs. Sadly, it might not be in the marketing interests of either company.

The last question of this email: with so many digital compact and bridge camera makers allowing the use of wide-converters and teleconverters on their cameras, which is the most common (and therefore affordable) lens thread (58mm, 55mm or 52mm) among aftermarket conversion lenses?

Thanks for your patience and time.

Thanking you.
Yours truly,
Aditya Govindarajan


***
*** ANSWER 1
***

AG, your suggestion that DSLR manufacturers would be wise to include a movie mode with their cameras is a good one; however, it is not as easy to accomplish as simply locking the mirror in the ‘up’ position. In fact, there are already DSLRs that offer mirror lock-up for the purpose of avoiding camera shake caused by any sudden movement of the mirror while the shutter is open, yet such cameras still do not include a movie mode.

The biggest hurdle to DSLRs having a movie mode is their mechanical shutter. In movie mode, an electronic shutter typically operates at 30 fps. Considering that the average lifespan of a mechanical shutter is 100,000 cycles, the mechanism would wear out after approximately one hour of movie mode usage. AG, you would literally have to change your shutter every time you charged your battery. :)

At this point, you might be thinking to yourself, why not just leave the mechanical shutter open and use an electronic shutter. Again, a good suggestion, and again, one that is not so easily accomplished. Due to the problems of ‘bloom’ and ‘smear’ normally associated with electronic shutters (see “Question 2—- Electronic Shutters In Full Bloom” of the October 15, 2006 Gary’s Parries), most DSLR image sensors do NOT use electronic shuttering, or if they do use it, it is ONLY in combination with a mechanical shutter, which then serves merely as a light blind to reduce the bloom and smear.

In movie mode, however, a DSLR’s mechanical shutter cannot be used as a light blind (due to the ‘wear and tear’ issue mentioned above), so the problems of bloom and smear would remain. The solution would be to design an image sensor that simulates the dark exposure start and dark image transfer of a mechanical shutter, but this would require additional circuitry at each photosite, which would use up more of the photosite’s valuable photosensitive area, thus resulting in smaller photodiodes and correspondingly higher image noise.

And the problem does not end there. Most DSLR image sensors do NOT even have a video output, which would be a necessity for implementing a DSLR movie mode. So you see, AG, not only would you need the mirror lock-up, but also a completely redesigned image sensor.

One way around this problem is to dedicate a second, smaller image sensor specifically for movie mode utilization. The Olympus E-330 already has such a CCD for its full-time, live preview mode. The E-330 would therefore be a natural for the addition of movie mode capabilities.

As for the Sigma DP1, it remains to be seen whether this APS compact will offer movie mode capabilities. It all depends on whether its Foveon X3 image sensor has an electronic shutter and video output. Current indications are that the X3 will offer a movie mode, and that it will use its VPS (Variable Pixel Size) feature to internally group blocks of pixels together as one, so that image data can be output from the chip at frame rates suitable for movies. Of course, if the DP1 has a movie mode, there is no reason why the Sigma DP14 ‘DSLR’ (which uses the same X3) could not have one, as well. :)

Speaking of video output frame rates suitable for movies, since the main advantage of the AVC/H.264 compression you mentioned is for high-definition (HD) video resolutions, it might take a while before digicam image sensors can offer such high-resolution video output at frame rates suitable for movies.

On the matter of converter lenses, unless you already own a collection of such lenses, I would not worry about a camera’s particular thread size, as most of the popular thread sizes are well supported.

[Note: Thanks to Nick in Japan for submitting this accompanying Canon 20D photo, which illustrates his ‘custom’ version of a DSLR with a live view movie mode. Get well soon, Nick. We miss you. – GP]

***
[Column photo “The Photographer” by Brenda LaFleur of Brenda LaFleur Photography.]



Tracker Pixel for Entry

Your Comments

Comments

No comments yet. Post a comment below!