Incident metering in bright sunlight

[brambor]

I use an incident meter with my M3. It appears that it exposes properlu indoors and under overcast conditions but when I bright sunlight itseems to overexpose by a stop. Do you have similar experience?

[blakley]

What kind of meter?

 

If you use a meter with a dome, and you're not very careful about the angle at which you hold it, you can get "too much" or "too little" of the dome looking at the sun or sky. Try angling the meter different ways to see if this helps; alternatively, try a flat diffuser if your meter supports one and see if that helps.

 

Finally, of course, you should zero your meter - but I presume you already know that; instructions for zeroing should be in the manual.

 

When you say "seems to overexpose by one stop", how are you evaluating this? Are you comparing it against the readings of one or more other (presumably accurate) meters? Looking at slides? Looking at negatives? If you have a digital camera with manual exposure settings, it may be very instructive to use it as the meter indicates and then take a look at the resulting histograms in a variety of lighting situations.

[bill_carriger2]

Bob,

I've not heard of zeroing a meter. How is that done? I use a Sekonic L-508 and the operating manual does not mention zeroing. Thanks.

[blakley]

"Zeroing" a meter means putting its sensor in complete darkness (by covering it, for example) and adjusting it to make sure it reads zero in that state. The L-508 doesn't have a zero adjustment control, but it does have exposure compensation, which can be used to adjust the meter's sensitivity to your preferred level.

 

<a href="http://www.photo.net/bboard/q-and-a-fetch-msg?msg_id=000zG1">This thread</a> describes how to set exposure compensation on the L-508.

[ronald_moravec1]

Zeroing a selenium meter is making the meter read zero when there is no light hitting the cell or with the battery removed from a Cds or SBC meter.

 

If you are overexposing in sunlight, the proper exposure is 1/ISO at f16 at 40/50 deg N or S latitude in full sun with no haze in the air and the sun at your back. If the meter is telling you f 11 is correct, and you get overexposures, the meter is to blame. If it tells you f16, and there is over exposure, the shutter speed is probably running slow.

 

Check the shutter by going in open shade and shooting a series at 100-500-250-125-60. All should have the same density if you adjust the lens. If not, it is repair time or understand the high speed(s) run long and adjust for them being off.

 

Before I sent my cameras to DAG, I had corrected/marked shutter speeds taped to the bottom of every M body. Meters go to Quality Light Metric in Hollywood Ca. I no longer futz with stuff out of calibration.

[charles_stobbs3]

Isn't there a rule of thumb that you go to the subject wit the incident meter and point it at the camera position to get a reading? (I've never actually used one.)

[eliot_rosen1]

Incident meters are usually better than standard reflected light meters when there is a range of different lighting in the scene. However, the incident meter still doesn't know what proportion of the incident light will be reflected and it assumes that it will average out to medium gray. I would think, therefore, that if the scene has mainly high reflectance subject matter (eg., white snow, sand, etc.), the meter would "think" that less light would be reflected and would tend to over-expose. You still have to apply corrections for lighting conditions even with an incidence meter.

[kelly_flanigan1]

With a self powered meter, the cell is a current source, with current proportional to light, with the cell driving a low resistance coil. <BR><BR>The meter is basically almost short circuited in the meter coil, and swings due to DC currect.<BR><BR> IF the cells contacts are slighty resistive, the meter will read ok at low light levels, and a low meter reading at high light levels. <BR><BR> This is like a bad battery connection on a car, the radio and dome light work well, the starter wont turn over with a high current demand.<BR><BR> Its almost a given that an older cell will get a resistive contact when you have old age and humidity. Most all the meters I have fooled with that were declared dead, or "low readers", have dirty contacts, fixable with a pencil eraser. <BR><BR>Imagine placing a 0.1 ohm resistor in line with your car battery. A 1 amp radio will only have 0.1 volts drop, so 13.2 volts is then 13.1. With a 100amps from a starter, the drop would be 10 volts!

[david_d4]

"Isn't there a rule of thumb that you go to the subject wit the incident meter and point it at the camera position to get a reading? (I've never actually used one.)"

 

 

 

This is what I was wondering too. Pointing the meter the wrong way (at the subject, as you would with a reflected light meter) will still give good results on overcast days because the light is very diffuse and non-directional. In sunlight you'll overexpose if the sun's behind you and underexpose if you're shooting into the light.

 

It's one possibility. My apologies Rene, if you already know this, I just mention it for the benefit of anyone else reading this thread in the future who's new to the incident meter.

[brambor]

Sorry to be late to this. I posted the question and went hiking with kids. Now I'm back after coming home, processing a roll of film and making him dinner.

 

My meter is Sekonic L351. I definitely know that I need to point the meter back at the photographer. FWIW today at the hike I compared reading in full sunlight with the meter and with meter in Canon 1V and wouldn't you know it they came back the same. So it's just my crying over overexposing frames that I would love to get just perfect... ;-)

[Rob F.]

Let's think about this. In bright sunlight, the subject may or may not be fully frontally lit. If it is, then pointing the meter at the camera should also result in pointing it directly, or almost directly, into the sun. That would give the minimum exposure.

 

But when the subject is not fully frontally lit, the meter will be pointed somewhat away from the sun, giving a somewhat fuller exposure. Yet, there will probably still be highlight areas that are just as bright as if the subject were fully frontally lit (contrasty light). Those areas would now be at risk of overexposure.

 

So it might make sense, in a case like that, to temper the meter reading with knowledge of the sunny 16 rule, and/or point the meter dome more at the sun, to avoid blowing out the highlights.

 

I don't know if that has much to do with the problem you've been having, Rene, but since your results sound like they are variable, maybe this has something to do with it.

 

My 2 cents . . .

[fran_ois_courtois]

I totally agree with Rob: sunny 16 only works if you point directly to the sun, e.g., for landscapes or subjects uniformly and totally lit by the sun. In other cases (portraits) the rule usually becomes a "sunny 11" because people usually do not turn their head up towards the sun, wear hats, etc ... There are exceptions if the ground is very reflective (snow, beach, ...) : then the sunny 16 is verified whatever the angle ...

[ronald_moravec1]

Some advocate pointing the dome between the key light and camera. I find this works well with studio lighting, not paricularly well with outdoor pics. In any case it is about 1/2 stop less exposure.

 

Do not adjust for light or dark toned subjects, unless you want to have them rendered a little dark in the case of snow or a little dark in the case of a coal pile . The whole idea is to take those decisions out of the process. That is the reason movies are metered with them. They can`t be reshot or bracketed. Incident meters work all the time every time providing everything else is calibrated correctly.

[kelly_flanigan1]

You need to see if you have a meter linearity problem, ie dirty cell contact, or cockpit error in using the incident light meter.<BR><BR> The whole purpose of using an incident light meter is better control, thats why movie chaps started using them in the 1930's and 1940's, since the burn rate in dollars/hour is huge. <BR><BR>When the lighting ratio is too high, ie too deep shadows, no meter is going to give a magical reading that works. <BR><BR>In movies you measure the lighting ratios, and fill the shadows with more light so the scene maps its image onto film well. <BR><BR>Outdoors bright sunlight is harse, shadows can be very deep, you are using a wider range in brightness compared to an overcast or indoor shot. Here movie chaps often fill the shadows using reflectors.<BR><BR>A modern muliticoated lens will have deeper, darker shadows than an old scratched uncoated lens that adds flare to the shadows, and lightens them.<BR><BR>If your meter has a tad of linearity at the top end, you will be learning Kentucky windage to use your meter in bright scenes. Then if you use another meter that is OK, you may start underexposing at high light levels. A meter cal shop if decent should check the linearity of your self powered meter, so you are not doing Kentucky windage.

[roland_haid]

Yes, that is right and the reason that I have not used incident light metering for years. That is true for chrome (Positive) film only. The reason for this is the definition of film speeds for all films (including print and B/W) and the calibration of the meters to that. Read Jeff Conrads excellent explanation on light metering basics. For slide film the contrast outside (bright) is to high and needs correction up to 1 stop minus to avoid burned highlights (Jeff Conrad). An other possibility is to direct the meter to the sun (Q.G. de Bakker) which gives more or less the same result. In overcast and indoor conditions light meters trends to underexpose or show neutral readings as highlights aren't simply there there is nothing to fade out. For reflected meterering, its the other way round. It often overweigts the sun or sky a in bright condition. Thats what we need for Positive film

[brambor]

I just scanned my film from yesterday and yes, the subject is overexposed with the use of reflective meter. I think in situations like these I just have to close down a stop or brackett.

<p>

Yesterday's hike and blueberry picking. (after considerable burning)

<img src=http://static.flickr.com/61/202736664_3bb7998f6b_o.jpg>

[george_b1]

From the National Geographic "Field Guide" (Second Edition. page 148):

 

". . . In some situations, you may need to deviate from an incident meter's recommended settings. With a bright subject (like snow) decrease exposure slightly to retain texture. With a dark subject - - such a black cat in a shadow - - increase exposure slightly. This is contrary to the reflected exposure metering technique, but is correct with an incident meter."

[henry_a]

Rene,

 

This is not a metering problem, its a development problem (or more precisely an exposure and development problem) In this case I think about 20% shorter development time would have saved you. If you know in advance that you will shoot the whole roll in conditions like this you can expose it a bit more and cut development time further.

 

As for incident metering technique in this instance if you had held the dome toward the light source (the sun here) you would have gotten better results as far ar the highlights are concerned - the skin tones would not have been blocked up. Of course Sunny 16 would have done that as well, no meter needed. And in either case the shadows might have gotten a bit thin.

 

Next time you go out in these conditions, set your film speed one to one half stop slower (if you're at 400 now set it to 200-250) and cut your development time by 20% (maybe 25%) and see if you don't like that better. I think you will.

[jtdnyc]

Both reflective and incident meter readings may require adjustment when the subject matter is extremely reflective, such as a polar bear against white snow, or non-reflective, such as a black cat in a coal mine. The adjustments will be in oppposite directions, but that isn't the whole story. Equally worth noting is that the reasons for the adjustments are different.

 

Reflective readings require adjustment because the meter is calibrated for medium gray and extreme subjects therefore "deceive" the meter.

 

Incident readings, on the other hand, require adjustment NOT because of a calibration problem but because the subject matter falls outside the brightness recording range of the sensitive medium, film or sensor.

 

Thus, if film had, say, 20 stops of exposure latitude, the incident reading would be valid but the reflective reading would still call for adjustment for ideal exposure.

 

This may seem like an academic distinction, but I find that understanding what's going on with my meters helps me achieve appropriate exposure in tricky situations. YMMV.