Incorrect data in Info panel

[jonbarber]

With my 20D, I am seeing incorrect or confusing data in the Info panel, as follows:

• the "shutter" data consists of only one digit, i.e. "2" or "3", when this is no longer sufficient precision to nail down an exposure.  Admittedly, this may not be a problem except at a few shutter speeds, but I use those speeds!  Does "1" mean "1" or "1.6?" Does "2" mean "2" or "2.5?"

• the EV data seems weird.  When I increase exposure, the EV number decreases, at least in the frames in question here.

20D body is using firmware version 2.0.3; Photomechanic is release 4.4.3.3

Thanks for any light anyone can shed on this....

[dennis]

Jon,

You are correct about exposures greater than 1".  PM is (incorrectly) rounding this to the nearest whole second.  So 1.3 seconds will show as "1" and 1.6 seconds will show as "2" (and 2.5 seconds will show as "3").  I've fixed this to show 1 decimal point of precision for these shutter speeds greater than 1 second.  Thanks for pointing this out...

Regarding EV, if you "increase" the exposure, e.g. by longer shutter or bigger aperture (smaller f number), then EV goes down because that means the scene is darker.  The EV is independent of ISO (i.e. it only depends on aperture and shutter speed).  If you want to consider the ISO as well, then use the {bv} "brightness value" variable in PM which is relative to ISO 1.  So at ISO 100, BV = EV - 5.  If you increase the ISO you decrease BV (e.g. BV at ISO 200 is 1 less than BV at ISO 100).

See http://en.wikipedia.org/wiki/Exposure_value for more info.

PM uses APEX units for reporting {ev} and {bv}.  See http://en.wikipedia.org/wiki/APEX_system for more info.

In the next release of PM we also added an {ev100} variable which is BV at 100 ISO (or {bv} + 5).

--dennis

[dennis]

Jon,

Also forgot to mention 1/1.3, 1/1.6, etc shutter speeds.  These will also be fixed in the next PM rev (i.e. 1/1.6 or 0.625 seconds is currently showing as "1/2" instead of "1/1.6").  We could show 0.625 for 1/1.6 and 0.769 for 1/1.3, but I think it makes more sense to always show 1/x for shutter speeds less than 1 second since this is what the cameras usually show (e.g. Nikon shows 1.3 for 1/1.3 seconds, and 1.3" for 1.3 seconds).

--dennis

[jonbarber]

Dennis,

Nice of you to respond so quickly...PM is a great program, with great support.

I'm gonna have to think about your second post a little while I have the camera in hand, but the fixes proposed for the exposures of over 1" to 3" sound good.  I see your point about trying to keep consistent with the traditional 1/x notation that's common to cameras, but I must say, I've never liked numbers that mixed decimals and fractions, e.g. 1/1.6.  Maybe I can get used to it.

The EV thing wouldn't even have occurred to me, except that I was trying to correlate the exposures I knew I had set with what PM was showing.  When I saw two frames showing the same shutter value when they were in fact 1/3 stop apart (and visually different) I looked at the EV for guidance. 

But I'm lost; I thought a higher EV number indicated a greater amount of light (and of course, a lighter looking exposure) yet when I look at these two frames, the lighter one bears a lower EV number.  When
I increase exposure time, I get a lighter rendition (denser negative, thinner slide, pixels piling up on the right end of the histogram, :-))  Then again, I've never paid much attention to EV; I've never really needed it.

I look forward to the next PM release, even though I probably have to pay for it....

[dennis]

But I'm lost; I thought a higher EV number indicated a greater amount of light (and of course, a lighter looking exposure) yet when I look at these two frames, the lighter one bears a lower EV number.

Jon,

Perhaps you are thinking of exposure compensation where a positive number increases the brightness.  But yes, EV is a measure of available light and the more light there is, the higher the EV.  Therefore, when you increase the exposure (larger aperture or longer shutter speed) it means there is less light available, so the EV goes down.  It can be confusing since a positive EV compensation means a lower scene EV.

--dennis

[jonbarber]

Thanks for trying, Dennis.  It's a good thing that EV isn't a concept I often need, 'cause until I get a new brain, it may be too advanced for me.  But I'll study....