Spot metering or "ambient"reading for equipt. shots

[michael_darrah]

For some time now I've taken my 35mm gear with me to work to record

some of the "more memorable" moments that occur there. I work

outdoors w/high voltage equipment and some real interesting sights

occur occasionally.

I've recently purchased a Hasselblad 501 cm kit w/ a few extra

acessories and a sekonic 508 spot/ambient light meter.

A few days ago, some of the men on my crew had the opportunity to use

some rather large earth moving equipment in preparation for an

upcoming high voltage cable installation job. I wanted to record the

progression of work in MF. As I prepared the camera and film backs I

wondered which function of the sekonic meter was going to give me the

most accurated reading for exposure. I was a day of rapidly changing

lighting situations. First sunny and then totally overcast. I tried

spot metering of the equipment itself for some tight shots, and then

went to ambient measurement just to see if the two readings would

match. They didn't. I've mostly relied on the spot function of this

meter since I've purchased the Hasselblad, but I've not had any of my

exposed film developed yet. Can someone tell me which method, spot

or ambient, should have been used to determine exposures in this

situation. Any instruction, opinions, ideas, or even a verbal

flogging would be greatly appreciated........

Thanks

Mike

[david_goldfarb]

A spot reading will tell you how to set the camera so that the thing you point it at will be recorded as a value equivalent in luminosity to a neutral grey card. If you point it at a bright white object, your image will be underexposed. If you point it at a black object, your image will be overexposed. If you point it at a properly oriented 18% grey object (there is some debate about how this object should be positioned for the best reading--check out the archives), then you should get the same reading as you would with an incident meter (there is also some debate about how the incident metering dome should be oriented with respect to the light source and the camera--again, check the archives for all the theories).

 

Unless you are photographing things that actually emit light (I don't know--arcing wires or arc welders or whatever), I would go with an incident reading for now, then read about spot metering to learn how to determine the tonal range of a scene and use that information to match your exposure and development to your film (see, e.g., Ansel Adams, _The Negative_).

[ellis_vener_photography]

I think by "ambient" metering you mean incident metering.

Incident metering is where the meter measures the light falling

on the subject. This is different from a reflected light meter -- like

a spot meter -- where the meter reads the light reflected back by

the subject. <P>

Unless you know what you are doing with a spot meter, which

takes just a little practice and some head scratching, probably

the incident metering method will be more reliable and will

certainly be quicker.<P> Using either the spot or incident method

you'll get the best results if you first calibrate your system. This

involves finding out what your film's true speed is, and also the

accuracy of your camera and lenses shutterspeed and deviation

(if any) from what the true �-stop as marked is, and finally how

accurate your meter is.<P>But back to your question: If you are in

a position where you can meter the light falling on your subject,

using incident mode, I'd try that. I would not expect the incident

and spot meter readings to agree at all, but for both to be correct

--after you have interpreted the spot readings by taking into

account the reflectiveness of your subject.

[kevin_kolosky]

Michael

 

I totally agree with Ellis. I would only add that when and if you start developing your own black and white film and want to try the zone system come on back onto photo net and we'll tell you why you should then start using the reflected meter to help you control the contrast of your negatives.

 

kevin

[andreas_carl]

For your purposes the incident metering would probably work best. Both methods can give you accurate results, but the learning curve is steeper with the spot meter. If you get into serious black and white photography, where you will match film development times with the contrast range of the scene, that's where the spot meter will really shine. Otherwise, stick with the incident method. Just my opinion of course...

[michael_darrah]

Very much thanks to you who answered my query. Although now I'm not looking forward to getting my first few rolls back. I guess thats how to learn though. I'll read some more threads here and find some books on light reading and go back to work to try to understand this facet of photography.

Again, many thanks to those who answered.......

Mike