Using a dSLR as a light meter

[Samriel]

I'll probably be getting myself a 8x10 Wista by next week, along with a good tripod, some film holders, darkcloth etc. However, a light meter is not included in the package. Now I've read that one could technically use a dSLR's light meter instead to adjust the exposure settings for your view camera.

As I'm new to film photography (35mm, MF, LF or otherwise) and haven't familiarized myself with darkroom work and the Zone System in practice, I'd like to know how this can and should be done, and what are the advantages and disadvantages compared to the use of a spot meter.

Thanks upfront.

 

[Steph]

Well, if you are not bothered about the zone system, you could meter the scene with your dSLR as your normally would and use those settings on your LF camera (not forgetting to take into account filters, bellows extension...). If the dynamic range of the scene falls within the dynamic range of your sensor, chances are they you'll be fine with negative film. When you read about the zone system, you'll understand how a spot meter might be useful to maximise the dynamic range you can record on film.

 

[Samriel]

Hmm, so to use the Zone System I'd definitively need a spotmeter. Many people were suggesting the Pentax Digital Spotmeter, but somehow it's not as easy to find in Japan. What is commonly sold and auctioned here is the Minolta F Spotmeter. Any idea if this would do the job as well as the Pentax?

So lets say I'm using my dSLR to meter the exposure, and I get a desired exposure of F8, 1/250s, ISO100 on my dSLR with a 50mm lens (APS-C). How would I translate that to my view camera, assuming I am using no filters etc.? Basically, can someone teach me EV calculations, or at least point me to a online or book resource where I could read up on in?

 

[pete_6109]

I shoot 4x5 and medium format and I use either my Minolta Meter with a 5 degree spot attachment or my Pentax 1 degree spot meter. I don't actually use the zone system. I use a simplified version of the zone system that has worked for me. I meter on the darkest part of the scene that still holds detail and subtract 2 to 2-1/2 stops giving less exposure than my meter says. Sometimes, depending on the scene, I will also read the brightest part of the scene that still holds detail and then average the shadow reading with the highlite reading. Then I use that setting on my dslr to take a picture to see if I am getting the exposure I want. If all looks good I set my 4x5 camera for my new calculated exposure and shoot the picture. This usually works for me.

 

[Samriel]

I will start with a series of noobish questions:

I shoot 4x5 and medium format and I use either my Minolta Meter with a 5 degree spot attachment or my Pentax 1 degree spot meter.

What do the degrees stand for? What is the practical difference between a 1-degree and a 5-degree meter?

I don't actually use the zone system. I use a simplified version of the zone system that has worked for me. I meter on the darkest part of the scene that still holds detail and subtract 2 to 2-1/2 stops giving less exposure than my meter says.

Why do you do that? Wouldn't that lead to loss of detail in those areas, or imply that the meter is off? What kind of results do you get?

Sometimes, depending on the scene, I will also read the brightest part of the scene that still holds detail and then average the shadow reading with the highlite reading. Then I use that setting on my dslr to take a picture to see if I am getting the exposure I want. If all looks good I set my 4x5 camera for my new calculated exposure and shoot the picture. This usually works for me.

So basically you are using the spot meter to tell to get a desired exposure for your dSLR. I guess the lightmeter gives you the EV value (never used one, no idea how it actually works), and you adjust the exposure according to it. How do you determine your aperture, shutter speed and ISO based on the EV? Is there some kind of formula to calculate all this, and if there is, could you explain it in detail or link to some more detailed description?

 

[Steph]

So lets say I'm using my dSLR to meter the exposure, and I get a desired exposure of F8, 1/250s, ISO100 on my dSLR with a 50mm lens (APS-C). How would I translate that to my view camera, assuming I am using no filters etc.? Basically, can someone teach me EV calculations, or at least point me to a online or book resource where I could read up on in?

Well it is easy. If you use ISO 100 film, set your shutter speed at 1/250s and your aperture at f8 and you're good to go. If you use a different ISO it is just a matter of adding/subtracting the corresponding number of stops.

 

[Steph]

What do the degrees stand for? What is the practical difference between a 1-degree and a 5-degree meter?

It is the angle of view of the spotmeter. 1 degree is more accurate than 5 degrees (it reads the light from a smaller area).

 

[Steph]

I think the best way to go about the whole thing is probably to read Ansel Adam's books. He is the one who invented the Zone System after all:

[ame="http://www.amazon.com/Camera-Ansel-Adams-Photography-Book/dp/0821221841/ref=pd_bbs_sr_2?ie=UTF8&s=books&qid=1226567190&sr=8-2"]The camera[/ame]
[ame="http://www.amazon.com/Negative-Ansel-Adams-Photography-Book/dp/0821221868/ref=pd_bbs_sr_3?ie=UTF8&s=books&qid=1226567190&sr=8-3"]The negative[/ame]
[ame="http://www.amazon.com/Print-Ansel-Adams-Photography-Book/dp/0821221876/ref=pd_bbs_sr_4?ie=UTF8&s=books&qid=1226567190&sr=8-4"]The print[/ame]

Once you have read those you can decide for yourself if you want to use the Zone System (it is quite involved) or your own simplified version and from there decide what equipment you need.

 

[Samriel]

Thanks for the info Steph. I actually ordered the three Adams books just a few hours ago.

Well it is easy. If you use ISO 100 film, set your shutter speed at 1/250s and your aperture at f8 and you're good to go. If you use a different ISO it is just a matter of adding/subtracting the corresponding number of stops.

Is there nothing else to it? Just copy my settings straight to the view camera, and I'm done? It sounds too simple to be true.

 

[Steph]

Is there nothing else to it? Just copy my settings straight to the view camera, and I'm done? It sounds too simple to be true.

Yes it is that simple (if you don't do close-up/macro work, in which case you have to take into account bellows extension). Actually, ou can make it as easy or as complex as you like. Obviously a spotmeter and the zone system will give you much more control than metering the whole scene with a dSLR.

 

[JC1220]

You will need to test your DSLR against your film results, most people find anywhere from a 1/3 to 2 stop difference with using a DSLR as a light meter for LF. Without testing, at the least over expose by one stop. In the field, you will never use a stop less than f8, if you use anything less than f22 I would be surpised as well. A simple ambient reflected and incident lightmeter is more accurate and easier than using your DSLR.

 

[JC1220]

I think the best way to go about the whole thing is probably to read Ansel Adam's books. He is the one who invented the Zone System after all:

I think Fred Archer would take umbrage with that.

 

[Steph]

I think Fred Archer would take umbrage with that.

. OK. Would it better to say: 'He's the one who invented the Zone System in collaboration with Fred Archer' or would you prefer 'Archer came with the ideas about the Zone System and Adams formally described the process'?

 

[JC1220]

. OK. Would it better to say: 'He's the one who invented the Zone System in collaboration with Fred Archer' or would you prefer 'Archer came with the ideas about the Zone System and Adams formally described the process'?

:lmao:Whichever, you choose! AA gets far too much credit for certain things in my book.

 

[ksmattfish]

Your DSLR with a longer focal length lens is a spot meter. A spot meter is just a reflective meter capable of metering small areas in the scene.

Obviously personal film testing is in the works as you are using the zone system. You will also need to do some personal digital testing to see how to set up the DSLR to get accurate measurements for the film exposure. Set to the same ISO my Canon 20D was about 1/3 stop more sensitive than my Sekonic lightmeter.

In the end you are going to want a meter. Large format gear is big and bulky. After you fill a backpack with the camera, lenses, and accessories you'll still need to haul the tripod, and a bag of film that'll probably be larger than your DSLR bag. A light meter that fits in a pocket somewhere is going to be nice.