LightMeter tutorial - DPChallenge Forums

12/30/2011 10:29:29 AM · #1

Hey Ya'll,

I recently bought a Sekonic L-358. I read the manual and understand how to use it but I was wondering if any of you can give me some tips on how to get it to really sing.

I need to adjust my camera differently from what the LM recommends after the test shot. If I input the suggested values the pictures aren't exposed correctly. The reason I bought the thing is to alleviate this problem...

Does anyone know of a reputable tutorial online?

Thanks in advance!

Canon EF 24-70mm f/2.8L USM

12/30/2011 10:35:38 AM · #2

You can find everything from these videos, including light meter and is I am not mistaking there are a few videos for those to show you how to use them.

Try this link

Message edited by author 2011-12-30 10:40:36.

Giles

Canon EOS-5D Mark III

12/30/2011 10:39:27 AM · #3

are you checking histrogram or just the lcd play back? id check on your comp as well, my lcd doesnt match up well to my screen often look over exposed on the lcd then ok on computer,

Samsung Galaxy S21, S21+, S21 Ultra

12/30/2011 10:45:10 AM · #4

Thanks

FocusPoint, Unfortunatly I am at a government computer and I am denied access to YouTube. I'll watch them when I get home. I seem to think of these things when I am work... Must be boredom ;-)

Thanks

Giles_uk, I first noticed it after I transferred the shots to my computer. Almost always it is pretty underexposed.

Do I need to calibrate it? At this point it is almost useless...

Bear_Music

Sony 24-70mm F4 Vario-Tessar T* FE OSS

12/30/2011 12:20:32 PM · #5

Are you using it as a flash meter or as an incident light meter? IN other words, are your problems when trying to set the correct exposure for strobes, or do they come when you are metering the ambient light falling on the scene?

In general, for any light meter to work properly with your gear you need to calibrate it to the actual (not stated) ISO at which you are shooting and the actual (not stated) shutter speeds of your camera.

Regarding shutter speeds, you can send the camera in to be calibrated, and ask for a chart of actual shutter speeds; this is something pros do regularly, at least with the big film cameras. I'm not sure it's a viable option for we hobbyists anymore.

For the sake of argument, look at it this way:

1. An incident light meter (with the little dome thingie) reads the light falling on the scene and gives you an exposure that will, if everything's accurate, render all the tones in the scene accurately; your blacks will be black, your whites will be white, your zone 5 gray will be rendered accurately. The light meter accomplishes this by telling you "At ISO 100, set the lens to f/8 and the shutter speed to 1/125 second (or whatever the values are) and the tones will be rendered accurately.

2. If you do what the light meter says EXCEPT you set the camera at ISO 200, you will get 1-stop overexposure. If the indicated ISO is 100 but the *actual* sensitivity is 200, ditto.

3. If you do everything the light meter says but your shutter is sticky so an indicated 1/125 is actually 1/60, you will get 1-top overexposure.

4. Likewise, if the aperture is not calibrated properly, or is not closing all the way during exposure (sometimes the case if it has gotten gummed up) your exposure will not be accurate.

5. Finally, of course, the light meter itself must be accurately calibrated to begin with; typically, no two of them are the same.

6. So as you can see, you have 4 variables: meter, aperture, shutter, and ISO -- any or all of these can vary from the designed or indicated specifications.

Now, in a practical sense, what's a guy to do? Well, you need to start testing. But how do you do that when you don't know if ANY of your variables are on-spec? You start by realizing that ISO accuracy and meter accuracy can be effectively linked. In other words, if your meter's off by 1 stop and your ISO's spot on, you'll compensate by changing the indicated ISO to "calibrate" your camera to the meter, and the same would be true if the camera's ISO is off by a stop and the meter's spot-on. OR any combination of the two.

Let me explain: when you're calibrating a light meter to a camera (or a film, for that matter) what you want to do is find an ISO to dial into the light meter that produces accurate results with the nominal ISO of the camera (or the film). So, for one reason or another, after testing, you may find that when the camera's at ISO 200 the meter needs to be at ISO 160 (or whatever) to produce nominal results with that particular camera. This could be because the light meter's off, or it could be because the cam,era's ISO is not as stated (very common), it doesn't matter. You compensate by changing parameters at the meter.

Now, since you don't know if your shutter speeds are nominal or if your apertures are accurate, how can you test? You do it by shooting your first tests wide open (so the aperture doesn't have to close down) and at a longish shutter speed (to minimize % variables in inaccurate shutters; usually they go off at the high speeds). So try shooting some tests of a calibration target (white through black stripes and a zone 5 patch) wide open in a dim enough light to require shutter speeds in the 1/4 second to 1 second range. Use these shots to determine your actual ISO performance.

This is just ballpark stuff, but it's a viable approach.

Once you've standardized on a match between the camera and the meter, as far as ISO goes, you have eliminated the major variable, and now you can start testing at different apertures and shutter speeds to see if there are any anomalous areas where results fall above or below the desired baseline.

Phew...

That's enough for now...

R.

12/30/2011 01:10:21 PM · #6

Wow, thank you for taking the time to explain that!
I will take your advice and go test by test until I find where the variance is.

I did notice, however, that the exposure is wrong when I set the light meter to take a measurment when I fire the flash.

For example, in a room, at night, incandesant bulb over head, softbox to the right.

A: I don't know how to read if my flash is to strong/close.
B: When I transfer the setting to the camera the exposure is wrong.

I know it is something to do with the flashes...

12/30/2011 01:18:00 PM · #7

Let's see if I can he;p since I do work in the studio almost fulltime.

These settings are default, you should try and see if they work.

Set your camera to ISO 200, Shutter speed 1/125 and F stop 11

Now, I assume you are using two flashes, if so

set your main light steady, about 6-8 feet from your subject.
set your fill light other side same distance

Have your meter set to 1/125 and ISO 200. Face its dome to the main light and fire flash. Edjust the flash's power until you read F11
Other flash should be set half stop lower (for default), could be low one stop.

Let's see if this helps. You can always play with the F stop, make it 10-9 or 11 until you get a satisfying tones. You must face the meter's dome to the flash and place it where ever the focus point of your camera would be, like nose, or eyes area, not the belly area.

PS: White balancing camera also helps. We usually do that after read the meter, but double check after the white balance.

BTW, I might be WAAAAY off what you're asking... sorry if I am :-\

Message edited by author 2011-12-30 13:31:39.

12/30/2011 01:34:37 PM · #8

Well that might be the problem.

I ALWAYS point the meter straight ahead to the camera from the focuspoint. (with the dome extended)

I assumed you make adjustments to the camers/flashes based on the readout, not the otherway around like you stated.

See? these are the things they don't tell you in the manual.

When I get home I'll give it a try. thanks again...

12/30/2011 01:38:40 PM · #9

Originally posted by sinistral_leo:

and those things covered on those videos... let us know if you like the videos and find them useful.

PS: Don't take my word though. after all everyone does it differently. Your technique could be correct as well, measurement could taken directly to the camera after lights are set... F stop should not change but if it does, you still have to continue adjusting the lights.

Message edited by author 2011-12-30 13:42:12.

Canon EF 24-70mm f/2.8L USM

12/30/2011 01:47:14 PM · #10

Well I am sure it is me.

Thanks again, I'll let you know what I was screwing up!

strew

Canon EOS-7D

12/30/2011 02:06:16 PM · #11

when you meter, you meter the light as it would hit the subject. do not point the dome to the camera.... point to the light source this will give a truer reading.

12/30/2011 02:31:37 PM · #12

Originally posted by strew:

when you meter, you meter the light as it would hit the subject. do not point the dome to the camera.... point to the light source this will give a truer reading.

Thanks, but I just got this from the manual.

2. When the Lumisphere is raised
This is used to photograph people, buildings, and other three dimensional objects.
Measurements are basically made by the method of measuring with the lumisphere aimed in
the camera direction (more precisely, in the direction of the light axis of the lens) at the position
of the subject.

I am confused...

Samsung Galaxy S21, S21+, S21 Ultra

12/30/2011 02:41:12 PM · #13

Originally posted by sinistral_leo:

Originally posted by strew:
when you meter, you meter the light as it would hit the subject. do not point the dome to the camera.... point to the light source this will give a truer reading.

Thanks, but I just got this from the manual.

2. When the Lumisphere is raised
This is used to photograph people, buildings, and other three dimensional objects.
Measurements are basically made by the method of measuring with the lumisphere aimed in
the camera direction (more precisely, in the direction of the light axis of the lens) at the position
of the subject.

I am confused...

What videos show is to aim meter to the flash and meter tham to find out half or full stop differences between the main and fill light, and other lights if you're using, then aim to the camera and take a measurement. If you read F11 from main and F9 from filling, when you aim the meter to the camera you should be able to read F10. That F10 can be also measured if main is 10 and fill is 10 which you don't want that for a portrait, so you aim the meter to the flashes first to find out good reading. I do it that way, 11 to 9 and still keep my camera at 11... gives me good results. So, you seem all those things are correct, depending on what you want to do. Outside, with no flash or one direct flash, I would aim the meter to the camera. As long as you have close readings, you should not have a burnt areas on your subject. I will hate to myself saying that but if you also use RAW, dynamic range can be fix with some PS work too.

Bear_Music

Sony 24-70mm F4 Vario-Tessar T* FE OSS

12/30/2011 03:25:36 PM · #14

What it boils down to is:

1. When you're metering a scene, you want the light falling on the lumisphere at the same angle the camera's seeing the scene from. So for a landscape, you stand in front of the camera and point the lumisphere at the camera. If you have a SUBJECT closer than "far away", you'd stand at the subject and point the lumisphere at the camera. That's how you do it in the studio, or outdoors when doing an outdoor portrait etc etc.

2. When you're setting up lights, you point the lumisphere at each light in turn, so you can meter the differential between them and adjust that. But when you're ready to shoot, you revert to 1 above.

That's basically it. You have to scope out for yourself how to set the particular meter to measure strobe exposures, they all do it differently. But the principle's the same.

R.

12/30/2011 03:31:57 PM · #15

Dittos, Bear ;)