Real Time Metering - "OTF" equivalent

Graham_RM13 · 4 May 2009

Film cameras had OTF metering that provided real time metering. Are there any Digital cameras that have the equivalent of this ?

If there are any technical experts that can explane the problems with providing the equivalent functionality of OTF metering I'd like to know about it

Thanks

seriousrikk · 4 May 2009

What is the equivalent functionality, ie what does it offer over current metering?

Jayst84 · 4 May 2009

Sorry, I don't know much about OTF metering. Has it not been super-seeded by TTL flashguns though?

HoppyUK · 4 May 2009

Off-The-Film metering in Real Time was useful for flash, but had no other benefits. A bit of a gimmick, frankly. In fact, the original Olympus OM2 needed a dual metering system, so you could have some idea of what the exposure was going to be, before it was actually made. And a daft pattern on the shutter curtains so that it worked at higher shutter speeds. Of course, Olympus made a marketing virtue out of this sillyness and sold shed loads.

You can't do it with digital as the surface of the sensor is like a dark mirror - not a nice matt grey like film.

The Contax RTS [Real Time System] from the 1970s was not 'real time' at all - just a bit quicker than the old school CdS meters of the time.

Graham_RM13 · 4 May 2009

HoppyUK said:
Off-The-Film metering in Real Time was useful for flash, but had no other benefits. A bit of a gimmick, frankly. In fact, the original Olympus OM2 needed a dual metering system, so you could have some idea of what the exposure was going to be, before it was actually made. And a daft pattern on the shutter curtains so that it worked at higher shutter speeds. Of course, Olympus made a marketing virtue out of this sillyness and sold shed loads.

You can't do it with digital as the surface of the sensor is like a dark mirror - not a nice matt grey like film.

The Contax RTS [Real Time System] from the 1970s was not 'real time' at all - just a bit quicker than the old school CdS meters of the time.

Several makers implimented it and it was extreamly useful for long exposures where the light was changing during the exposure. "Painting" a building at night with multiple discharges from a flash gun, balancing flash exposed forground subjects and dark backgrounds, control of the flash duration during exposure, were just some of the things that I used it for (and still do with slide film)

Now I have to experiment with the exposure and zero in on the amount of light needed to get it right (Huge advantage of digital) but this is only ok for static shots. The OTF system enabled this to be done for dynamic shots as well. Strobe firing the flash at 10-15 fps at fast moving subjects was another use of OTF, although you never quite knew how many flashes it would take before the camera closed the shutter.

While it may have been a gimmick to some, compared to having dozens of Automatic "Modes" that never get used, it was something that actually did a really good job of its intended functionality.

HoppyUK · 4 May 2009

With respect to you Graham, that sounds like gimmicky to me

Did any other mainstream manufacturers adopt OTF? I don't recall them.

I have tried most flash techniques, and never wanted or needed an OTF flash system. In fact, I don't quite see how OTF would help in any significant way in any of the situations you've mentioned. Am I missing something? :thinking:

Graham_RM13 · 4 May 2009

HoppyUK said:
With respect to you Graham, that sounds like gimmicky to me Did any other mainstream manufacturers adopt OTF? I don't recall them.

Indeed they did - If you Google "OTF Metering" there is a long list of makers that adopted the system

Olympus, Pentax, Minolta, Bronica, Nikon, Hasselblad, Mamia, etc...

"Canon initially were opposing the mainstream of this metering method, adopted by many others. They claimed their tests showed that the cell-in-the mirror-box method are more suited for aperture-priority AE mode. Canon also claimed Film plane (TTL OTF) metering systems posed some problems in using special films having a different reflective surface, including infrared film where they felt that TTL OTF system would limit the full performance of a professional-grade camera. Canon ate their own words by incorporating the TTL/OTF metering feature in the Canon T90 back in 1986 -"

HoppyUK said:
I have tried most flash techniques, and never wanted or needed an OTF flash system. In fact, I don't quite see how OTF would help in any significant way in any of the situations you've mentioned. Am I missing something?

With an OTF system I can set the aperture to produce the required DOF then open the shutter, use multiple flash heads or a single flash head fired multiple times to illuminate specific subjects in the composition then the camera will take this light and any ambiant light and at the correct total exposure it will close the shutter. The other way of using it was to directly control the flash by turning off the flash once sufficient light had reached the film.

OK it wasn't something that was used every day but it was something I used almost all the time I used flash. It also produced excellent ballanced light results in daylight and fill-in situations.

It will be interesting to see if it is resurected in future models. After all the makers need things to release to the market to keep them ahead. All it takes is one and the rest will follow (as they did last time)

I also miss "Multi-Spot" metering but that's another discussion

HoppyUK · 5 May 2009

Graham_RM13 said:
Indeed they did - If you Google "OTF Metering" there is a long list of makers that adopted the system

Olympus, Pentax, Minolta, Bronica, Nikon, Hasselblad, Mamia, etc...

Sorry, I meant that OTF ambient metering was not widely adopted. The requirement for needing a duplicate system for pre-exposure estimation being a major drawback. But for flash, yes it was a clever solution.

Graham_RM13 said:
With an OTF system I can set the aperture to produce the required DOF then open the shutter, use multiple flash heads or a single flash head fired multiple times to illuminate specific subjects in the composition then the camera will take this light and any ambiant light and at the correct total exposure it will close the shutter. The other way of using it was to directly control the flash by turning off the flash once sufficient light had reached the film.

Is this significantly different to current systems using a pre-flash to set exposure and balance multiple flash guns? They're not strictly real time and not OTF but it amounts to the same thing and seems to work with my four Canon 580EX guns.

For multiple light painting with a single head, you can do it automatically with any thyristor type flash with an on-board sensor (eg 580EX2). However, I do it manually, setting the power output with a bit of mental arithmetic (guesswork!) and a quick test flash (as you can with digital). I then try to fire the gun at an equal distance from the subject for even exposure. I actually don't like any automatic control for this kind of thing.

Graham_RM13 said:
It will be interesting to see if it is resurected in future models. After all the makers need things to release to the market to keep them ahead. All it takes is one and the rest will follow (as they did last time)

I agree that innovation sells, for sure. But OTF metering from the dark mirror-like surface of a digital sensor is not really possible. Olympus, the pioneers of OTF, are not using it. But digital practicalities aside, I don't really see any unique or valuable benefits to OTF.

Graham_RM13 · 5 May 2009

HoppyUK said:
...For multiple light painting with a single head, you can do it automatically with any thyristor type flash with an on-board sensor (eg 580EX2). However, I do it manually, setting the power output with a bit of mental arithmetic (guesswork!) and a quick test flash (as you can with digital). I then try to fire the gun at an equal distance from the subject for even exposure. I actually don't like any automatic control for this kind of thing...

Richard,

That is the very technique that I used before the OTF system came along. Using my big SunPak (30 years old and still pumping it out) I'm able to do just as you have described. This is fine for static shots and with the vast advantages of digitals instant results (especially with linked shooting to the PC) I can see instantly how I can adjust the light levels of the various subject areas.

Manually controlling, adjusting and reviewing results is so much like the old days of Polaroid backs, it is actually quite fun to photograph things in this way. Ultimatly you do get exactly what you work at achieving, which is very rewarding.

A digital equivalent of "real time metering" would not be an off the surface system as, principally it wouldn't need to be as the photosites themselves could be sampled to determine the exposure levels. With the advances in sensor sampling rates, I can't believe that a real time metering system would be at all difficult.

Thanks for a real discussion...

Cheers

HoppyUK · 6 May 2009

"Thanks for a real discussion..." You're very welcome bud

Reading data off the sensor. Now you're talking! Don't get me started on the wonderful range of benefits that this would (will

) bring. Not to mention getting rid of the shutter, mirror, OVF etc. A long list of ground breaking stuff. I started a thread on this recently, centred around the new Samsung 4/3rds pre-production camera. The debate was long and a bit heated at times, but I was really disappointed with the luke warm reception that was given to the concept in general.