I find that my Pentax spot meter doesn't really work that well at close distances - would putting a close up lense on the meter (say +3 diopter) enable the meter to more easily distinguish exposure values at close range? Or is there a better way?

-- fw (finneganswake@altavista.net), September 04, 2001

Answers

In my opinion, the 1º of the Pentax should be able to meter everything you need. If your shooting close up with your camera, you should be able to meter the small area without a problem. What results are you getting? Underexposure? If you are doing macro work, are you figuring bellows factor into the equation? Cheers

-- Scott Walton (f64sw@hotmail.com), September 04, 2001.

Scott ; yes, the problem arises on macro work, where I believe that I am correctly taking account of both the bellows and reciprocity factors (and subsequent devlopment adjustments), but the meter doesn't seem to distinguish exposure values close up in the same way as at normal distances - hence the starting point in determining the exposure range seems to be flawed, and I seem to end up with far too much contrast in the negative. Hence I am looking for a way to make the meter work more effectively at close distances - maybe between 9 and 12 inches away from the subject.

-- fw (finneganswake@altavista.net), September 04, 2001.

40.5mm close up lenses will do the trick I use a #3. George

-- George Nedleman (gnln@thegrid.net), September 04, 2001.

If you can locate a copy of "Beyond the Zone System," Phil Davis includes plans for a modified Pentax spotmeter. The modifications he outlines are meant to convert the spotmeter so that it functions as a densitometer. This is similar to the conversion you are thinking about and it may help. One other thought: Are you shooting in a studio setting using tungsten lighting or outdoors? If you are shooting with tungsten, you may need to lower your film speed. As a general rule, ISO ratings for tungsten lighting are lower for any given film when compared to daylight. Good luck!

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-- Dave Willison (dwillisart@aol.com), September 04, 2001.

The specifications on page 28 of the Pentax 1º Digital Spotmeter instruction manual states the measuring distance as being "from about 1.5m to infinity". Whenever I've metered macro subjects I have used a close-up #3 and have never experienced a problem in Colour or Mono.

WG

-- Walter Glover (walterg@netaus.net.au), September 04, 2001.

The meter shouldn’t care if the subject is in or out of focus. Adding the plus diopter just makes it easier for you to see what you’re metering.

Also, too much contrast would be an indication of a developing problem, not an exposure problem. Perhaps too much compensation for reciprocity.

Good luck,

Joe Dicke

-- Joseph A. Dickerson (jadphoto@aol.com), September 04, 2001.

While the meter doesn't care if the image is in focus, an out of focus image will not be metered as accurately. Say a high value and low value are adjacent. If the image is out of focus, the values "dilute" each other and your metering is out of focus.

Yes, a close up lens will help. Note that the meter, though, doesn't account for reciprocity failure nor bellows factor.

The close up lens will also help you see what you are aiming at.

-- Charlie Strack (charlie_strack@sti.com), September 04, 2001.

Attaching a close up lens would shorten the focal length of the meter's lens, and widen the reading angle. As a consequence of the shortened focal length, the lens aperture would also effectively be widened, and therefore the meter would no longer be accurate.
If the subject's that close, why use a spotmeter anyway?

-- Pete Andrews (p.l.andrews@bham.ac.uk), September 05, 2001.

Correction. As long as the lens combination is kept the same distance from the light-sensor there won't be any change in the effective aperture.
The defocused lens will be the one in error, since the out-of-focus light isn't concentrated onto the sensor area as much. There's probably a straightforward factor you could apply for close metering, something like: At 1.5 meters add 1/3rd stop to the reading; at 1 meter add 2/3rds stop, etc.

-- Pete Andrews (p.l.andrews@bham.ac.uk), September 05, 2001.

Pete:

The reason for concern I would assume, is for macro work, where a spot meter might be advantageous for small areas at close distance.

Charlie

-- Charlie Strack (charlie_strack@sti.com), September 05, 2001.