OK, this one gets filed in the Minolta folder. I thought the metering
was good but I didn't realize it's smarter than me. :-)
I also used the A1 in event photography although I kept it at ISO 100
and poured on lots of flash from studio units on the sidelines with a
Sunpak 422 in the hot shoe or on a bracket. I depended heavily on the
huge depth of field. It was impossible to focus in the dark but when
set at f/5.6 and focused at 4 feet (and taped in place) you from a bit
less than 2 feet to infinity. Even at 50mm equivalent you get from
5-1/2 feet to infinity when focused at 11 feet. Dance floors are
generally so dark that I would generally get more in-focus shots than
the guy shooting beside me with a 20D. In fact, it was hard to miss. :-)
Chuck Norcutt
On 2/2/2011 11:44 AM, Ken Norton wrote:
>> BTW, where did you learn all these design details?
>
> Reverse engineering and insider information.
>
> I had spent a long time testing and trying to understand the metering
> system. I had encountered anomalies which then required further research.
> The manual mentions the presence of EV evaluation, which then launched me
> into some backdoor research.
>
> In a nutshell, here is how the A1 (A2 and A200) meter the scene:
>
> 1. Focus is determined through wide-field analysis. The AF system will then
> determine closest subject within the coverage area. If using single-point,
> the camera immediately assumes that to be the subject to focus on. In a
> similar manner to the Nikon's 3D matrix metering, the Minolta determined
> foreground/background distances. As the lens and camera are a closed-loop
> system, the lens passes the distance information to the camera.
>
> 2. The matrix metering examines the exposure of the subject (active focus
> point) and the overall scene. The entire image area is averaged and the high
> and low points determined. Based on a special-sauce algorithm, the camera
> makes an assumption about the lighting and hence the scene. When in bright
> sunlight, the camera KNOWS it is in bright sunlight! When shooting a sunset,
> the camera knows it is shooting a sunset. When shooting interiors under
> artificial light, the camera knows it is indoors and in artificial light. It
> uses this knowledge to base certain rules on.
>
> 3. The subject exposure is weighted as the critical exposure. But based on
> #1, if the subject to background distance is about the same, the camera
> knows to not base exposure strictly on it, and in some cases may entirely
> ignore it and fall back on it's assumed scene. If the overall average EV of
> the entire image area is very high, the camera knows it is being fooled and
> will weight the scene to Sunny-16. If the overall scene is too dark, then it
> knows it is dark and won't attempt to up the exposure too much. Of course,
> this requires a single point of bright or dark in the image somewhere for it
> to base the evaluative on, otherwise it starts to fall back to dummer modes.
>
> 4. If using the flash, the camera will adjust flash exposure for the subject
> and aperture/shutterspeed for background. Nothing unique there, as all
> systems do that now, but Minolta's system can also include a pre-flash (if
> desired) to determine if the subject reflectance falls within what is
> expected and if not, it will offset accordingly.
>
> 5. If for some reason, the camera is not making sense of the scene. For
> example, if you have a polarizer on the lens and you shoot a photograph of a
> white car in the bright sun, the camera will likely underexpose the picture.
> Without the polarizer, the camera knows it is in bright sunlight, therefore
> ignore the really bright blob in the middle. With the polarizer, it no
> longer understands it is in bright sunlight and will use the focus-point
> (subject) and average to guess. The camera thinks that white car is a person
> and the background a darkened scene. So it will base the exposure on the
> focus point, underexposing the picture.
>
> 6. If the focus-point (subject) and average exposure are close to each other
> and the distance calculation for subject and background are close, (provided
> it was able to even determine distance--manual focusing or single-point AF
> disable some of this), the camera will fall back entirely to averaging.
>
> That's the clifnotes version. Olympus' ESP functions similarily, except,
> like the Canon and Nikon systems, it baselines the scene on a relative
> exposure basis because they don't always have knowledge of the nor the
> distance.
>
> Minolta lifted the algorithm from the Maxxum D7 film camera, which has
> arguably the second-finest metering system in any film camera. (OM-4Ti
> obviously being the best...). Also note, that this technology is
> cross-licensed across the manufacturers so if it seems to be somewhat
> familiar, it's because it is. Just like the Nikon F5 system, it is
> spectacularily good, but when it is fooled, the failures are equally as
> spectacular. Five exposures will be dead on and the sixth will be four stops
> off.
>
> A little case history of the A1, A2 are in order. Minolta hadn't released
> the D7D yet and used the A1 and A2 as their test environments. The reason
> the cameas are so powerful and feature rich is not an accident. These two
> cameras were their pro cameras (minus the sheer performance) and even today
> are unmatched in many areas. The A2 quickly arrived after the A1 (six months
> later), but had certain trade-offs. Regardless, the professional flash
> system that Minolta had (and is still in use by Sony) is not only
> outstanding, but in some cases better than either Nikon or Canon's best.
> Essentially, the A1 and A2 is interchangeable with the Latest/greatest Sony
> DSLR and only now are we starting to see a few of the features (especially
> the 3D matrix metering described above) being fully implemented in DSLRs.
>
> For professional use in event photography, the A1 is a great camera--if you
> stay within the strict confines of its strengths. AF is slow and noise is
> high. The lens, though, is simply among the best in any camera ever. That GT
> lens is mind-boggling good!!! And it has that 28-200 equivalent focal length
> range, so I never have the desire to swap lenses mid-stride. There is some
> distortion at some focal lengths, but overall, the lens doesn't possess the
> nasty cross-over points which some zooms have. When shooting events with the
> A1, it is my preferred Stroboframe camera! I manually focus the lens (no AF
> delays), place the Vivitar 285HV flash on Yellow Auto and put a UltraBounce
> modifier on it. In almost every case, I use ISO 200, which is a true 320 on
> my A1) and that gives me a working aperture somewhere around F5.6. F5.6 on
> that format gives me unheard of DoF, so focusing is a non-issue. Oh, and
> since the flash syncs at nearly any speed, I typically use aperture-priority
> auto-exposure (averaging mode), with around -2.0 exposure compensation.
>
> The RAW processed files clean up very nicely (Thank you RSE), are
> exceptionally sharp and the colors are good. Not Olympus good, but still
> quite good.
>
> My girls have inherited the A1 since I got the DMC-L1, but I still use it
> quite a bit. If Minolta didn't have such quality-control issues with the
> D7D, I would have gone that direction instead of the E-1. Overall, I'm glad
> I stuck with Olympus, but if it wasn't for a concerted effort by Bill Barber
> to keep me in the fold, I'd have definitely gone with that system. The
> higher-end Sony cameras are Minolta cameras. The lower-end Sony cameras are
> Sony cameras. Some cross-over exists, but you can tell where the
> "consumer-electronics" and "PlayStation3) aspects of product design kick in.
>
> AG
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