On Sun, 6 Oct 2002 21:27:04 GMT, "Tom Thackrey" wrote:
>On 6-Oct-2002, "Zuiko" wrote:

>> I'm wondering if using TTL with a grey card is better than incident
>> meters.
>> When you set a camera to f2.8 and 1/125, the actual exposure will be
>> different with different lenses because some lenses have more light loss
>> than others. That's why movie lenses use T-stops instead of F-stops.
>> So...
>> are we just wasting our money with incident meters?

>TTL has other advantages, like you can meter through the filters on the lens
>so you don't have to figure in the filter factor.

This is unfortunately not true for most colored filters.
There is about 1/2 the exposure loss error in many (all?)
TTL meters due to their color errors. This is easily checked
by metering a large grey area without the filter, then
metering it with the colored filter (at the same angle,
in the same light, and with the same framing). It is likely
that the exposure difference will be about 1/2 what the
filter factor supplied with the filter would predict...

>The difference between T stops and F stops in most lenses is insignificant,
>probably less than the meter error alone. If you are really worried about
>precise exposure you would test your film batch, camera, lens, meter, and
>developer combination to, by shooting a test roll and measuring the results
>with a densitometer, get an EI for the combination.
>
>Personally, I find a separate exposure meter to be much easier to use than
>the camera and a grey card, particularly a meter with incident, spot and
>flash capabilities.

I've always wondered why there were almost no averaging
incident and 30-degree direct reading meters - this
would appear to give a near-ideal metering much of the
time (both incident and direct-reading methods fail
easily with non-middle-tone subjects [in reverse
directions], but combining the reading types should
give a useful compromise exposure).