Help understanding how to use light meter

Skeeterfx20 · May 15, 2019

Ok this is my first light meter. Prior to getting my Mamiya RB67 I never needed one. I have the Sekonic L308x-u.
I have the basic functions figured out. However my question is do you have to take into consideration the focal length of the lens? For example if I compare the light meter with my camera light meter with a zoom lens i cant get a match. Also the reading are different at each focal lenght.

I am over think or just missing a step?

Pieter12 · May 15, 2019

Have you read the manual? Are you using it in reflected or incident mode? With a TTL meter and a long focal length, you might be isolating an overall brighter or darker part of the scene and get different readings. Try focusing on a grey card and comparing readings (using the meter in reflected light mode).

Skeeterfx20 · May 15, 2019

I figured it. Focal length has nothing to do with getting the correct exposure. I just applied my understanding of exposure in combination with the light meter. To confirm my understanding was correct I used my dslr. First I just took the first photo using the cameras metering. The next photo I took a meter reading. Made the adjustment according to the actual details of the light and subject. Worked like a charm both ways reflective or incident. Tried it on the barn outside and my wife inside the house.

To be honest I love the light meter photos a lot more than the ones from the camera meter.

I may not be expressing this properly but in any event it was pretty easy to figure it out after I spent some time thinking about it.

nmp · May 15, 2019

Skeeterfx20 said:
I figured it. Focal length has nothing to do with getting the correct exposure. I just applied my understanding of exposure in combination with the light meter. To confirm my understanding was correct I used my dslr. First I just took the first photo using the cameras metering. The next photo I took a meter reading. Made the adjustment according to the actual details of the light and subject. Worked like a charm both ways reflective or incident. Tried it on the barn outside and my wife inside the house.

To be honest I love the light meter photos a lot more than the ones from the camera meter.

I may not be expressing this properly but in any event it was pretty easy to figure it out after I spent some time thinking about it.

The f-stop takes care of the focal length.

Ariston · May 15, 2019

The focal length to the film plane changes with the bellows focusing of an RB. There should be a scale next to the focusing knob of your right hand that tells you how much to compensate, if I am remembering correctly. Maybe it is at the bottom of the bellows.

Willyekerslike · May 15, 2019

Skeeterfx20 said:
Demonic L308x-u

Whilst I have often thought that light meters were the work of the devil I had not realised he had brought his own line of them out.

Auto spell correction argggggg......

Skeeterfx20 · May 15, 2019

Lol yep auto correct, fixed it

MattKing · May 15, 2019

Ariston said:
The focal length to the film plane changes with the bellows focusing of an RB. There should be a scale next to the focusing knob of your right hand that tells you how much to compensate, if I am remembering correctly. Maybe it is at the bottom of the bellows.

This only matters when working really close - less than 10 x the focal length is a good rule of thumb.

chriscrawfordphoto · May 15, 2019

In most cases, an incident meter will give better results than a reflected light meter. Here's an explanation of it that I wrote last year.

Introduction to Handheld Light Meters

Kodachromeguy · May 15, 2019

Chtis, your notes and instructions are excellent. Thanks for going to so much effort.

AgX · May 16, 2019

Skeeterfx20 said:
I figured it. Focal length has nothing to do with getting the correct exposure.

It has to do.

In light metering the angle of view of the meter can get crucial.

At hand-held meters it may range from over180° down to 1°. (Depending on the characteristics of the meter and how you use it.)
Similar at through-the-lens metering at various focal lengths.

As long as the object has a gradual change of luminosity over its spread, different viewing angle of the meter will yield different result.

L Gebhardt · May 16, 2019

AgX said:
It has to do.

In light metering the angle of view of the meter can get crucial.

At hand-held meters it may range from over180° down to 1°. (Depending on the characteristics of the meter and how you use it.)
Similar at through-the-lens metering at various focal lengths.

As long as the object has a gradual change of luminosity over its spread, different viewing angle of the meter will yield different result.

That's certainly true for reflective meters, but with incident meters as long as the meter is reading the same light that's illuminating the subject it doesn't matter.

Any reflected light reading is going to require knowing what part of the subject is being metered and how you want to expose that portion. I avoid reflective meters other than very small spot meters like the Pentax 1 degree since knowing what they are reading is hard except maybe when you are close enough that you could use an incident meter.

AgX · May 16, 2019

L Gebhardt said:
That's certainly true for reflective meters, but with incident meters as long as the meter is reading the same light that's illuminating the subject it doesn't matter.

Incident meters too have different viewing angles from obout 90° up to over 180°. And even the 180° ones have to be directed to the camera as they too have a declining sensitivity over their half-angle.

This declining sensitivity is necessary to mimic the varying reflection of the object depending of the angle under which its surface is lighted.

Skeeterfx20 · May 16, 2019

I never used a hand meter, never had to for what I liked to do. However I quickly found out it isn't much different from using my meter in my camera. I shot two rolls of Fuji V 50 today and developed them. What I did was take a hand held meter reading then adjusted it to the scene, which meant sometimes I had to open up a stop or two or stop down a stop or two. Just to make sure I did bracket. I was fine everything came out like I expected it would. Now that was just with the reflective setting.

When I get time I will play around with the incident just to check how to get the best results.

Now if I would have just taken a reflective reading with no adjustments some photos would have worked and others would not have.

This may be too simple of an explanation but I will say if I wasn't experience in exposure I would be having big problems. I'm not a technical guy in terms of the correct terms. I just figure things out from what I habe learned.

John Koehrer · May 16, 2019

And there you go. Zone system simplified! Actually you can interpret the same way with an incident meter too.
You're getting zone V and using the same logic, you're off.

Sirius Glass · May 16, 2019

When using a reflectance meter, meter without the sky in view. Meter the subject, not the sky.

Luis-F-S · May 16, 2019

A man who has one watch will always know the time. A man who owns two watches will never know the time.

chriscrawfordphoto · May 17, 2019

Kodachromeguy said:
Chtis, your notes and instructions are excellent. Thanks for going to so much effort.

You're welcome. I'm glad that it was helpful.

AgX · May 17, 2019

Skeeterfx20 said:
I never used a hand meter, never had to for what I liked to do. However I quickly found out it isn't much different from using my meter in my camera.

A great number of meters, and for sure all advanced models, yield the feature of incident metering without hassle.
Not so cameras.

(At the few finder cameras who got the resp. diffusor cap that cap is typically missing...)

Some meters yield the great feature of "placing" luminance values as the Gossen Profisix.
Hardly any camera does so (aside of Canon T90 with similar meter).

Some meters yield the chance to meter flashes.
Hardly any camera does so (again T90 to some extent)

L Gebhardt · May 17, 2019

AgX said:
Incident meters too have different viewing angles from obout 90° up to over 180°. And even the 180° ones have to be directed to the camera as they too have a declining sensitivity over their half-angle.

This declining sensitivity is necessary to mimic the varying reflection of the object depending of the angle under which its surface is lighted.

All incident meters need to be directed at the camera, and capture a wide field to sample the light falling on three dimensional subject. I’ve never tested a range of incident meters but between the two I have the incident readings are very close to each other, but there is more variability with reflectance readings unless right up to the subject. That’s why I only use spot and incident in the field, though I’m sure one can learn to meter accurately with only a wide field reflectance meter. But it just can’t be as accurate.

AgX · May 17, 2019

There are incident meters with diffusor domes (that are shaded differently beyond 180°, depending to casing design) and there are flat diffusors, standard for selenium meters and applied on small sensors instead when metering for flat objects has to be made.

John51 · May 18, 2019

My mf cameras don't have meters. I guess at Sunny 16 and then check against my incident meter. I'm getting better but am still wrong often enough to keep using the meter.

removed account4 · May 18, 2019

Hi Skeeter

Unless you are using your camera to do macro work with bellows extension, you do not have to worry about any light meter adjustments.
Its only when you put a 40mm lens ( for example ) and extend the camera out to 80mm to do 1:1 sorts of close up photography that you need to worry about extra light.

Have fun with your new toys
John

Sirius Glass · May 18, 2019

jnantz said:
Hi Skeeter

Unless you are using your camera to do macro work with bellows extension, you do not have to worry about any light meter adjustments.

Not so! I discovered at a workshop that my meter was off and sent it out to be recalibrated. That made a big difference. Any meter can need recalibration.

macfred · May 19, 2019

... don't follow leaders, watch exposure meters ...
B. Dylan - Subterranean Homesick Blues

Help understanding how to use light meter

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