Musings on Photography

Stupid Holdovers from the Film Era – Human Interface for Exposure Control

Posted in equipment by Paul Butzi on May 4, 2007


For a given scene, there are three variables the photographer can control to adjust exposure – film speed/sensor sensitivity, lens aperture, and shutter speed.  [Hey, smart alec insisting that we can vary the lighting or add filters to the optical path – sit down and shut up.  You know what I mean.]

In the past, when we all worked exclusively in the film world, we could adjust film speed only by loading the camera with a different film (or by changing our development plan for the film).  In practice, this mean that once we made our film choice, the film speed decision was pretty much made.  Camera design reflected this: lots of cameras read the DX film speed coding right off the film cassette and set the meter appropriately, and other cameras had film speed setting which was neatly out of the main stream of the controls that were available to be adjusted at the time of an exposure. 

That left two variables – aperture and shutter speed.  Not surprisingly, nearly every camera had a way to adjust aperture, and a way to adjust shutter speed.  On many more automated cameras, we had ‘aperture priority’, where you picked the aperture (and film speed), and the camera read the lighting of the scene using the meter and adjusted the remaining variable (shutter speed) to get the right exposure.  Likewise shutter priority, where you picked shutter speed and film speed, and the camera picked the one remaining variable.  Finally, we had cameras that offered ‘program mode’, where you’d set the film speed, and the camera would propose a set of aperture/shutter speed combinations that would result in the right exposure, and you could scroll back and forth to choose one of these combinations.

But now we shift into the digital world, and suddenly there’s no particular reason why we need to set the sensitivity once, make a series of exposures, and then set it to something different, etc.  Suddenly sensitivity is a first class citizen in the world of exposure variables.

Why, then, do current digital camera designs not reflect this?  Sensor sensitivity is still treated like a second class variable in the exposure equation – setting it is far more complicated and slower than adjusting aperture and shutter speed.  And although we have program mode, sensitivity is really treated badly there.  We get to scroll back and forth through a list of shutter speed/aperture combinations, but there’s no possible way to fix, say, shutter speed and scroll through sensivity/aperture combos, or to fix aperture and scroll through shutter speed/sensivity combos.  There are no cameras that will let you fix shutter speed and aperture, and have the camera adjust sensitivity to match the lighting.

Again, the camera design engineers are still thinking about digital SLR’s in terms of evolutionary changes from film based SLR’s, and this is coloring how they address the fundamental issues of interface design.  It’s time for them to wake up, smell the digital coffee, and start thinking things through from first principles instead of relying on film-based camera design experience which isn’t applicable in the world of digital photography.

A digital SLR is not a film based camera with the film replaced with a digital sensor.  The camera manufacturer that figures this out and starts offering camera features which exploit the real potential of digital photography will be the manufacturer that gains market share.

[Attention Camera Manufacturers!  I am available on a consulting basis to help you figure this stuff out.  My rates are very reasonable.  Feel free to contact me via email.]

12 Responses

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  1. Allen George said, on May 4, 2007 at 8:58 pm

    There are no cameras that will let you fix shutter speed and aperture, and have the camera adjust sensitivity to match the lighting.

    I think using the “Auto ISO” function in M mode on the D80 should give you this behavior. Also, the Pentax K10D has a “Shutter/Aperture priority” mode that does exactly what you describe.

  2. Colin Jago said, on May 5, 2007 at 1:06 am

    There are a number of appealing things about the Pentax, including the inclusion of the ISO into the automation. I also like the idea of being able to get the final histogram without taking a photo (it is much faster because the camera doesn’t have to write anything). Somebody at Pentax has worked out that dSLRs are a different breed, even if the solutions are still very version 0.1

  3. Oren Grad said, on May 5, 2007 at 9:25 am

    My Pentax K110D has a limited Auto ISO function, as does its antishake-enabled twin, the K100D. These are among the least expensive DSLRs on the market, too.

    A minor historical quibble: during the era from the late 1960s into the 1980s when increasingly complex exposure automation was implemented via analog circuitry, exposure compensation settings were typically implemented through the same variable resistor as the film speed setting. The controls were often literally coaxial, and setting compensation amounted to just re-setting the film speed, albeit with control markings that made it clear that you had departed from the default. So in that sense, sensitivity really was in the heart of frame-to-frame exposure control.

  4. Oren Grad said, on May 5, 2007 at 9:28 am

    A PS: no, of course you weren’t actually changing the sensitivity of the film by resetting the compensation, just hijacking the sensitivity parameter to work around how the meter was controlling the other two parameters.

  5. Martin Doonan said, on May 5, 2007 at 10:05 am

    Can I have ISO bracketing, please? Could be as part of an extended AEB function.

  6. JohnL said, on May 5, 2007 at 4:16 pm

    ”A digital SLR is not a film based camera with the film replaced with a digital sensor.”

    . . . but isnt that the myth that camera manufacturers have us believe. The real point is until sensors are improved and reflect the needs of photographers this type of discussion will run because at present it seems sensors cannot give the range that was enjoyed by film. However I have to confess to the belief that the photographic world is being a tad harsh on digital because I remember many occasions as an ex pro where highlights were blown and shadow detail non existent in some situations – just as now. But now we all want more and now we cannot use the film/dev skills and experience we had to pull the highlights out of the fire! Its a pity we have to rely on the technology of one piece of equipment to give us what we need.

  7. John said, on May 5, 2007 at 6:17 pm

    The Sony R1 allows fast ISO changes. You just hold in a small button and scroll the main control dial–as simple as changing f-stops or shutter speeds.

  8. Rosie Perera said, on May 5, 2007 at 7:39 pm

    Paul, as a fellow EOS 5D owner, I think you’re whining a bit too much. Changing ISO on the 5D is a piece of cake. You don’t even have to hold in the small button (as with the Sony R1, as described by John above); you just press it once and you’re in a mode where you can scroll the main control dial to change the ISO. Press the little button again to get back out of that mode. I do this all the time and I don’t feel as if the setting is in an entirely different category from shutter speed and aperture. Sure, it would be nice to have a shutter/aperture priority mode that would automatically set the ISO for you appropriately. But there is still a meter readout that will tell us when we’ve got the thing exposed properly, so it isn’t too much trouble to go into manual mode, set the f-stop and shutter speed, and then flip the dial for the ISO until we get a proper exposure. And of course we’ve still got to use our brains and override what the camera meter says to us in certain situations.

    In response to JohnL’s comment, “But now we all want more and now we cannot use the film/dev skills and experience we had….Its a pity we have to rely on the technology of one piece of equipment to give us what we need.” — Hear, hear! Digital is great, it’s revolutionary, but it is also making us lazy and dumbing us down.

  9. chuck kimmerle said, on May 5, 2007 at 8:30 pm

    “but it is also making us lazy and dumbing us down”

    I don’t think that’s true at all. Digital may be making life easier for folks who are already lazy (hence the increased hoard of mediocre “fine art” photographers), but I doubt serious photographers will be dumbed down merely by a small bit of technology. The camera is only a tool, be it film or be it digital. If we allow it to make us lazy, we have only ourselves to blame.

  10. Adam Maas said, on May 7, 2007 at 7:34 am

    The K10D also has an ISO priority mode (called Sv for Sensitivity Value) where you set the ISO and the camera picks aperture and shutter speeds. Pentax has been pushing the interface and automation envelope with the K10D.

  11. JohnL said, on May 7, 2007 at 3:17 pm

    chuck – “but it is also making us lazy and dumbing us down”

    I think that may be a very pertinent statement.

    Prior to digital photographers, pro or otherwise had a wealth of camera/lens/film/developer/enlarger/paper configurations and by pure stint of hard work, time and hours of experimentation did we learn to use all those means to produce the end.

    With digital we seem to be going round in circles spending more and more money and time on technology which seemingly is not good enough or cannot produce the holy grail at this time.

    Until manufacturers produce what photographers need and not what they wish to produce then we have to just do our best – which is a pretty sorry state of affairs.

    I could go on ad nauseum but – and I include myself here, we have suckered ourselves into the digital scenario from taking an image, processing it, DAM’ing it, to printing it that we are on a seemingly endless treadmill of making do with what is available to produce what we hope is acceptable. Its only when we get very critical do we really question what is available.

    To close with one example – the Raw file, or the Raw files. How many are there? How have we let the manufacturers get away with the multitude of types locking us into a camera system instead of just a system? As stated, in my opinion this can be applied to each and every stage of the photographic process from conception to viewing.

    Sorry guys – semi rant over but hope I have made a point.

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