Would this be an efficient design for a cheap and easy spot meter lens attachment

[watch69]

I have a Canon AE-1 which has center weighted metering and rather than buying a light meter with a spot meter attachment I was trying to think of a way to get spot metering out of what I have or with minimal additional parts. What I came up with was this: buying a front lens cap and drilling a hole (somewhere around 0.5" or 0.25" diameter) so that light only reaches the lens through that small aperture and lands directly on the center of the lens. However, this would allow a very wide angle of light to pass through, so I was thinking of 3D printing a small cylinder out of black material with as little reflectivity as possible, with an inner diameter that is the same as the drilled hole, and making it long enough to get the viewing angle down to less than 5 degrees (maybe 2 inches long or so), and then affixing this to the lens cap. So basically it is a goofy looking attachable lens cap with a cylinder sticking out to only let in 5 degrees of light to the lens so that it falls directly on the center. Would this be an effective way for spot metering or would I get bad results?

 

[tirediron]

I think you would probably get no results. I don't think a tube of that dimension would allow enough light through it to trigger the meter.

 

[480sparky]

Your camera will still 'see' the black parts and read them accordingly. Result: Overexposure.

 

[astroNikon]

Easy enough for you to experiment your concept

Use flat cardboard with a hole in it directly over the lens for the first experiment.
Then use a cardboard toilet paper tube attached to a flat piece of cardboard (with an appropriate hole) to handhold over the lens to further experiment.

Then you can research how a camera meters. This is about digital cameras but will give you a good understanding, this one briefly talks about film ==> Understanding Metering and Metering Modes

 

[fmw]

If you have enough time to spot meter a subject, you have enough time to reshoot it if the matrix meter gave you a result you didn't like when checking it in the camera monitor. I sold my spot meter when I switched to digital.

 

[astroNikon]

If you have enough time to spot meter a subject, you have enough time to reshoot it if the matrix meter gave you a result you didn't like when checking it in the camera monitor. I sold my spot meter when I switched to digital.

The OPs Canon AE-1 film camera does not have a monitor to review images.

 

[Dave442]

That is why with film cameras we were always pointing them down at the ground and up at the sky. If you point the camera at something of one color and evenly lit then the center weighted meter is acting like a spot meter. As you know what you are looking at you know to go up or down with the meter adjustment to get it as if it was spot metering off the actual subject and then consider the highlights and shadows.

 

[Gary A.]

That is why with film cameras we were always pointing them down at the ground and up at the sky. If you point the camera at something of one color and evenly lit then the center weighted meter is acting like a spot meter. As you know what you are looking at you know to go up or down with the meter adjustment to get it as if it was spot metering off the actual subject and then consider the highlights and shadows.

Actually, that is more like an Incident Meter or Gray Card.

Get a Spot Meter. All the above posts provide reasons why your DTY device won't work. Unfortunately, handheld meters are not cheap. I'd look on the Bay or KEH for a used meter. Spot metering is my primary metering mode going back to the film only days. I know there are Light Meter apps for smart phones ... Maybe one of those apps has a spot meter mode.

 

[fmw]

If you have enough time to spot meter a subject, you have enough time to reshoot it if the matrix meter gave you a result you didn't like when checking it in the camera monitor. I sold my spot meter when I switched to digital.

The OPs Canon AE-1 film camera does not have a monitor to review images.

Yes, thanks.

 

[KmH]

About what a consumer grade 35 mm or 50 mm prime lens costs and allowing incident, reflected, and flash metering in 1/10 EV steps :
Sekonic L-308S Light Meter

 

[vintagesnaps]

Sounds like making a pinhole cap. They make those, or did anyway. But that isn't letting in much light and I guess you'd end up with a pinhole photo. Or, nothing, if you don't use the bulb setting and do a few seconds exposure.

I don't think it would work for metering because you'd need to measure the light coming in to the camera thru the lens not just what comes in thru a small pin hole.

 

[Dave442]

Option 2: a DSLR set to spot meter.

 

[Gary A.]

About what a consumer grade 35 mm or 50 mm prime lens costs and allowing incident, reflected, and flash metering in 1/10 EV steps :
Sekonic L-308S Light Meter

I don't think so ... An AE-1 with a 50mm goes all day long for less than $100 ... Probably closer to around $75-$80. I imagine a 50mm manual Canon lens would be around $20.

 

[dennybeall]

I recall needing spot metering one day when all I had was my Nikon "F" so I held my hand out in front of me at an angle and metered on that since it was getting the same light as the subject. Worked perfectly.