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02-03-2012, 08:24 PM   #1
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How to meter if you don't have a light meter?

Hi all, just got a Minolta Autocord TLR this week and it appears that it is working fine. Would like to take it out to shoot something tomorrow. However, the light meter that come with it have a mercury battery that is already out of stock (and after some search, found out it is unreliable with replacement battery). In this case, how do I meter? Based on my limited experience with dSLR, I can roughly estimate the shutter speed needed for a aperture, but would rather don't waste the film as they are kind of expensive

It comes with a 75mm F3.5 lens. Which, based on what I found, roughly equal to a 40mm lens on a FF camera.

Unfortunately I don't have a 40mm lens, can I put on a 50mm / 35mm lens on my K5, set the ISO as film ISO, set the F-stop, and find out the shutter speed needed?

Is there anything I need to be aware of? for example, is film ISO equal to digital ISO?

Is there any light meter that you would recommend? <$50 as well as <$100.

Thanks!

02-03-2012, 08:39 PM   #2
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The sunny 16 rule exist for that very purpose.
ISO=ASA for our purposes
In short, for sunny outdoors exposure is 1/ISO (shutter speed) @ f16
slightly overcast 1/ISO f11
overcast 1/ISO f8
very overcast 1/ISO f5.6
shadows 1/ISO f4

Shutter speed will be 1/ISO or the closest. For example, ISO100, you can go 1/125

Hope this helps!
Thanks!

PS
Using your K5 will work with any lens as long as you compensate for the distance. As long as you compose similarly, the reading should be useful.
02-03-2012, 08:49 PM   #3
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Thanks ismael!

I wanted to shoot in "Aperture Priority" mode (& like wide aperture whenever possible), though I realize it might not be possible as the max shutter speed is only 1/500. I forgot I can use the zoom lens on K5 to get metering. ><

well....hope my first roll come out OK.
02-03-2012, 08:52 PM   #4
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You can adjust the metering remembering halves and doubles.
1/125 f16 is the same as 1/250 f11 and 1/500 f8
double one, half the other

02-03-2012, 10:30 PM   #5
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I've done this before. It obviously will work. However, just be careful if you use any filters on your camera used for metering that you have the same filter on your other camera. If you're using a clear filter or a UV, it probably won't matter because those filters normally have a filter factor of zero. But, to be on the safe side check the filter manufacturer's web site to double check. Some filters like a skylight appear to have a filter factor of zero, but it's actually around +1/3 of a stop. A small amount, but it can never hurt to be accurate.
Also, when in doubt over expose. That is to say if your not sure between one exposure or f/stop or shutter speed, then choose the one that will let more light hit the film. It's always better to over than to under expose.

Have fun!
02-03-2012, 10:38 PM   #6
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I just got confused. How is 11 half of 16?
02-03-2012, 10:40 PM   #7
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You can set you DSLR to spot metering mode and you got yourself a very good spot meter. Just take several readings of the scene and set exposure accordingly.
02-03-2012, 10:59 PM   #8
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In the winter and above 30ish deg latitude, I'd use the Sunny 11 rule. Basically open a stop from the Sunny 16 rule. Low winter sun can often be weaker. And that goes for the time of day too.

02-03-2012, 11:03 PM   #9
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QuoteOriginally posted by callmeraymon Quote
I just got confused. How is 11 half of 16?
It's not. But try their squares, eh?

11^2= 121
16^2= 256
256/121= 2.1, tra la!

An f-stop is the ratio of the iris diameter (round) to the focal length (linear). Each f-stop in a sequence has half the area and thus passes half the light of the previous stop. So f/2.8 has half the transmission of f/2. That circular iris is a tricky devil.

Last edited by RioRico; 02-04-2012 at 04:43 PM.
02-03-2012, 11:10 PM   #10
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QuoteOriginally posted by callmeraymon Quote
I just got confused. How is 11 half of 16?
The area of the iris at F11 is twice as big as the area at F16, therefore allowing twice as much light to pass (or half if you look the other way around).
02-04-2012, 12:19 AM   #11
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QuoteOriginally posted by tuco Quote
In the winter and above 30ish deg latitude, I'd use the Sunny 11 rule. Basically open a stop from the Sunny 16 rule. Low winter sun can often be weaker. And that goes for the time of day too.
I live at 34* 13' 51" north and sunny 16 works fine for me. Well it did four days ago.
02-04-2012, 01:01 AM   #12
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QuoteOriginally posted by RioRico Quote
It's not. But try their squares, eh?

11^2= 121
16^2= 256
256/121= 2.1, tra la!

An f-stop is the ratio of the iris diameter (round) to the focal length (linear). Each f-stop in a sequence passes half the light of the previous stop. So f/2.8 has half the transmission of f/2. That circular iris is a tricky devil.
There we go. Throw some math in there and I'm good.
02-04-2012, 06:37 AM   #13
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Apertures are not linear.
In summary, full stops are:
f1.0 f1.4 f2.0 f2.8 f4 f5.6 f8 f11 f16 f22 f32

That means f4 is half de light (1 full stop) from 2.8 and twice (1 full stop) the light from 5.6

Shutter speeds are linear. So 1/500 is half the light of 1/250 and twice the light of 1/1000

So if you have an exposure of say 1/250 f11: You can play with it by doubling one and half the other like:
1/500 (half the light) f8 (double the light) net effect: same exposure
or
1/125 (double the light) f16 (half the light) net effect: same exposure

Thanks,
02-04-2012, 09:23 AM   #14
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QuoteOriginally posted by tuco Quote
In the winter and above 30ish deg latitude, I'd use the Sunny 11 rule. Basically open a stop from the Sunny 16 rule. Low winter sun can often be weaker. And that goes for the time of day too.
Ha! Ha! Yesterday in Portland at high noon with crystal clear skies, it was the Sunny 8 rule!

Back on topic...

There are a number of pocket charts available on the Web and in photo stores that list approximate exposures for various subjects and conditions.


Steve
02-04-2012, 09:42 AM   #15
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If you are going to get a light meter, I would not start with a spot meter--it is really a specialized tool. I would pick up a meter that does incident and reflected light. I would recommend something by Gossen or Sekonic. Minolta made very good meters as well. I use a Gossen Luna Pro SBC with can take attachment like a spot attachment--I believe some Minolta ad Sekonic meters also have attachments.

Incident meter is usually the easiest as it measures light falling on the object and so is not influenced by subject reflectance.
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