Exposure Compensation: Optimum control system

There was a very large  brightness range between direct sunlight on the stained glass windows and the darker parts of the interior.  Using the zebras on the windows I applied negative 1.33 stops of exposure compensation then adjusted the darker tones in the RAW file later in Adobe Camera Raw. The little G7 camera has handled the dynamic range decently well.  

I  think about and experiment  with various camera control systems.

Today’s post is an ergonomic analysis of approaches to the control of Exposure Compensation (EC).

I will use some actual cameras to illustrate points and show that there are ways to achieve optimal control of exposure compensation and ways to get it not-quite-right.

I was stimulated to write this piece by the almost simultaneous release of the Panasonic G7 and GX8 ILCs.  Although ergonomically similar these two cameras differ in their approach to the control of exposure compensation.

I have no idea why the designers at Panasonic chose to give each of these M43 cameras a slightly different HMI (human machine interface). 

My analysis leads me to the view that one of these systems is optimal, the other not-quite-right.

Principles as applied to cameras

There are four phases of camera use: Setup, Prepare, Capture and Review.

Prepare Phase comes in the minute or few in which the user prepares the camera for a new set of circumstances.  For instance shifting from “landscape” to “moving subject” or “hand held street “ to “tripod at night”  and so forth.  Adjustments in this phase are generally made with the camera held down, away from the eye. In this position the user can see the external parts of the camera and its controls.

Set-and-seemodules (engraved dials or other modules with fixed function such that the setting is visible on the module) are ideal for Prepare Phase.

Capture Phase describes the process of image capture. In this phase the operator is viewing through the EVF (or OVF or monitor) and optimally is able to adjust all primary and secondary exposure and focus parameters without having to lower the camera or alter grip with either hand.

Exposure Compensation is a secondary exposure parameter.  (Primary exposure parameters are aperture, shutter speed, ISO sensitivity).  As such it should be easily adjusted during Capture Phase.

The ideal control module for this phase is a dial with mode dependent function, which can easily be worked as described above.  This is  usually described as a Control or Command dial.

Set-and-seemodules are not ideal for Capture Phase for four reasons:

1. The dial  is invisible in Capture Phase. The parameter controlled by the dial therefore needs an EVF (+ monitor) readout and the dial will be operated as if it was a Control/Command Dial. 

The inscriptions on the dial are visible when they are not required (Prepare Phase) but are invisible when they are required (Capture Phase).

This distinction is highlighted (literally) if the camera has Zebras in the EVF for still photo. 
Note DSLRs cannot have zebras in the OVF, one reason I no longer use such cameras. 

Zebras can give an immediate visual indication of highlight clipping, allowing accurate EC to be applied before exposure. Inscriptions on an EC dial contribute nothing to this process.

2. The opportunity cost of assigning Capture Phase adjustments to Set-and-seedials is that 
Prepare Phase adjustments are excluded.  The G7 has a Drive Mode Dial which is very useful in Prepare Phase but the GX8 cannot have one as the place which a Drive Mode Dial might have occupied is taken up by the EC dial.

3. A twin dial camera (like the G7) becomes a triple dial camera (like the GX8) with two rear dials. Early reports from GX8 owners  are that some are happy with this arrangement, others find it overcomplex and awkward. Regardless of an individual’s likes, the triple dial setup is inevitably more complex than twin dials.

My studies of ergonomics indicate that if the job can be done efficiently with two dials, and it can, then three dials is redundant and imposes un-necessary complexity on the HMI.

4. In some locations such as the top right corner of the camera, the EC dial is forever prone to being bumped inadvertently, thereby applying unwanted + or – exposure.

In “safer” locations such as on the GX8 the dial is less likely to be moved accidentally but there is another problem.

If a Set-and-see EC dial is set to, say,  +1/3 then it remains there, whether that is appropriate for the current circumstances or not.

If a Control/Command dial is used to set EC it can be configured to default to zero on changing Mode or switching the camera off. This way you always start a photo sequence with EC at zero.

G7  Well implemented 2 dial system. Exposure Compensation can be directly adjusted with either the front or rear dial.

Twin Dial system, G7

The G7 is a very configurable camera.  Function of  the buttons and dials can be assigned  to the user’s preference.

For instance I have the front dial change Program shift in P Mode, Aperture in A Mode and Shutter Speed in S Mode.

In each of these Modes I have the rear dial assigned to adjust EC directly. If desired I could switch dial functions. This camera also permits one of the buttons to be used like the ‘alt’ key on a computer to assign different functions to the dials.

The HMI is streamlined, efficient and configurable.

GX8  Three dials to change values in Capture Phase but .....oops......... there is no place for the Drive Mode dial.

Triple dial system GX8

On the GX8 the EC dial does EC and that is immutable.

You get more dials and therefore more complexity yet the Drive Mode Dial has gone and you cannot reassign function of the EC dial.

The control system on the GX8 works, no doubt about that, but it uses three dials when two will do the job more efficiently and you lose the Drive Mode dial.

Comparison, FZ1000

This is my regular camera. It has zebras. It has a ‘one rear dial’ system with a front lever around the shutter button which can be used like a front dial for some functions.

I have it configured so the rear dial adjusts aperture in A Mode and Shutter speed in S Mode. I have assigned EC to the front lever. This is a fast, efficient system although it has a front/rear functional relationship which is the opposite of that which I use on the G7.

Summary

The use of Set-and-see dials for Capture Phase functions is not optimal on a modern camera. This applies particularly to Shutter Speed dials and Exposure Compensation dials.

I have discussed Shutter Speed dials elsewhere on the blog.

This post discusses Exposure Compensation dials.

I regard both as manifestations of a design process which preferences style over function.