Incident Light Metering

K

Kris

Guest
Alright, I will need to use handheld meter soon and have been doing some research on them.

Now the question: Sekonic manual says there are two type of incident light measuring techniques. The first one is with lumisphere in up position - for incident measurement. The second one is with lumisphere in down/retracted position - for light balance and simple illuminance. Can anyone gives this newbie some explanation on the differences?

Thanks in advance guys.
 
You read the manual?


I kinda just wing it. I keep the lumisphere over the light sensing thingy and take my readings as I walk around. I am careful to make sure I am pointing the Lumisphere towards my camera, or opposite the direction that my camera will be pointing (if your subject is in like light, ie open sunshine, you don't have to be right there at your subject to measure) and shoot away. In mixed lighting situations you have to be more careful of course, but same deal more of less. My 308bII came with another attachment, which I can't figure out what to do with, so it just sits in my bag. I can honestly say, that no matter how much I stressed over using a handheld correctly when I first got mine, it just worked and I have not had a "bad" exposure yet.
 
I'm eyeing on this second hand Sekonic L-408 and read the manual to see what kind of features it has. Sounds nice because it has spot metering capability to use in mixed lighting conditions.

There is one page that says about this two type of incident metering and you can set the lumisphere up or retracted by twisting the collar around the lumisphere. After Googling like crazy I still couldn't find any explanation on the two techniques. Not even from Sekonic website.

Oh well, just wait till I get my hands on it and lets see what it does. :rolleyes:

BTW, what made you decide for a collapsible Cron? I thought you had a Cron 35mm and 50mm already or you had only the 35mm?
 
No, I had the 50 and 35.

Now you know why I wanted a Chrome camera :), just a nice compact little lens.

I found the manual confusing too, so I just decided too much knowledge was, well, too much, and I just went out and started shooting. When this half of the world wakes up I am sure you will get more answers.
 
Kris, I have an older model (Studio DeLuxe L 398), so I took a look at Sekonic pages.
From what I understand, "Lumisphere in up position" is for incident measurement - like any other incident light meter. "Lumisphere" is used as Ralph (rover) said - just point it in direction of your camera and take a reading.
With the lumisphere retracted, you get only a flat diffusor, which is used to take contrast measurements: you get close to your subject, and take direct readings with it - several (or just two) measurements over light and dark areas, to give you an idea of the overall contrast.
My Studio DeLuxe uses a separate lumidisc for that, and I admit I never use it.
Basically, I just use lumisphere and take ordinary incident readings. Not much to it.

As for your meter, it takes incident, contrast, and reflected measurements. Contrast is what the cryptic sentence above refers to...
I'd go with just simple incident and reflected measurements - use reflected (with spot) to take more precise readings when you need them.

HTH,

Denis
 
I use the dome in up position for incident light mesurements of all 3d objects - when I shoot / "reproduce" a flat drawing, painting etc for later use as illustrations in books I have the dome retracted. this aplies for the 508 sekonic - on my old 328 sekonic I replaced the dome with a flat white plast thingy to get it into "retracted mode"
If anyone here has a Sekonic L328 but not the great spot mertering attachment I have just such an attachement piece in original mini belt bag plus the original domes and bag for the L328 (but not the L328) for 25 USD + postage send me a PM if you are interested - I will put it on E¤¤y next week if i gat around to it - ruben
 
Ok, I couldn't understand the contrast readings thing either. That is what the attachment I have hidden away is for, so I haven't done that. For general photography I don't think that is necessary anyway.
 
It pleases me to read that you are broke again, Rover. A fat PayPal balance is sick and wrong ;)

I meter the same as you and Denis; most often incident readings with the meter facing the camera and a spot meter for more critical measurements, critical on occasion meaning when I accidentally leave my incident meter at home :D

BTW, Congratulations on the M6!
 
Last edited:
I am happy that you exhasted your PayPal account as well, Rover. I was a bit nervous for you, as I had a bad experience with PayPal a while ago where they emptied my account and froze it.
 
Oh my god Nats!! I would not have reacted well to that. If I made it through without a stroke I would have been on the phone immediately with our state Attorney General's office and very publicly attacked Paypal. In a vertual world I think that when you deal with things like that you have to deal appropriately, but very strongly.

Well, I don't have that hole being burned in my pocket any more.
 
Denis, if I understand correctly, when the lumisphere is retracted the reading is more localised.

For example if you do northern-window portrait, you check the difference in brightness between the side close to the window and the face away from the window with lumisphere retracted then you set camera shutter speed/aperture based on reading taken with lumisphere up. Corect or not?

Ralph, with three Summicrons, I think you will need a second Leica body soon! :D
 
Kris, I can't help you much with Lumidisc - I don't have that model, but what it says for mine (L-398M) isn't very clear, either. It mentions footcandles, and use in situations where you have two light sources, one stronger, and one weaker. You point it towards one light source, make a reading, and then towards the second, and take another reading. Then you calculate "illumination contrast ratio"....
Too complicated, and I don't use artificial light, anyway. So, the plain ol' incident metering with lumisphere is what I usually use. Mine can also take reflected readings with the sphere replaced by a "lumigrid", but I've never used it, to be honest.

Regards,

Denis
 
Last edited:
As others have said, I just point the Lumisphere of my L-318B toward the camera (in the same light as the subject) and meter. I've never gotten a bad exposure this way.
 
I've got the answer :

...the dome retracted simulates the flat receptor cover of other meters. The flat receptor is used for flat subjects (such as copying) and for reading just one lamp at a time in a multi-source situation to determine lighting ratios.

Kindda incident spot metering I guess.
 
That is what I use the flat one for, one light metering with studio stobes to get the ratios set.

Todd
 
The best way to remember which receptor to use is to remember that the receptor is a "substitute subject." Its purpose is to integrate all the light that would fall on the subject, and use that information to generate an exposure reading.

So, when photographing a basically three-dimensional subject, such as a face, you want to use the three-dimensional receptor: the dome-shaped one.

When photographing a flat, two-dimensional subject, such as a book page or the surface of a building, you want to use the flat receptor. (On the newer Sekonics, this is simulated by retracting the dome-shaped receptor.)

This makes sense when you think about the effect of strong side lighting. If you're photographing a 3-D object such as a face, the side lighting will have a significant effect on exposure and needs to be included in the reading; so, you'd choose the dome receptor, which will pick up the side light the same way a face would. If you're photographing a flat object, the side light will just skim across it and have very little effect on exposure; so, choosing the flat receptor makes sure the meter will respond the same way.

Sekonic recommends using the flat receptor (or retracted-dome receptor) to measure lighting contrast because to do this, you need to measure each light separately. Using the flat receptor reduces possible "crosstalk" from other lights. However, if your incident meter doesn't have a flat (or retracted) receptor option, you can get the same effect simply by using your hand to shield the receptor from other lights.
 
One thing to keep in mind, though, when measuring contrast, you point the flat disc at the light source not at the camera.

Let's say you're taking a portrait using a fill light or reflector board. Aiming the dome toward the camera from the subject will give you the proper exposure, but not tell you anything about the relative contrast between the main and secondary parts of the subject. To find that, use the flat disc and while holding it at the subject aim it at the prime and fill lights. The ratio of the two will give you a number that you can always refer to for achieving the same look regardless of the correct exposure or overall brightness, which is found with the sphere.
 
You must log in or register to reply here.
Back
Top Bottom