Light meter refresher? when to use diffuser

[oceanbeast]

I recently began shooting medium format on a camera with no light meter built in. I have been using a handheld light meter but I don't know if I am using it appropriately. It is a Minolta auto meter VF.

I am confused as to under what conditions leave the white dome/diffuser on and under which conditions to take the dome/diffuser off.

For example I understand if I am shooting a back-lit subject I should use the diffuser and point the meter towards the camera for an accurate reading.

But wouldn't that in most cases overexpose the sky?

If you guys know of any online how-to videos or write-ups I would love to take a look, I haven't found anything as in depth as I would like.

And when is it appropriate to remove the diffuser?

 

[Ysarex]

Use a hand incident meter to measure the light at the subject position with the dome pointed back toward the camera. If you can't place the meter at the subject position then place the meter in the same light as the subject and again point the dome toward the camera.

Your understanding about using the meter with a backlit subject is correct. Yes that would in most, or more likely all, cases overexpose the sky. If you reduce exposure so as not to overexpose the sky you will then underexpose the subject. There is no exposure that get's them both right -- pick your mistake or correct your mistake by altering the lighting contrast. The meter doesn't fix bad light.

If you remove the diffuser you can use the meter to take a reflected light reading of the light bouncing off the subject (point meter without diffuser at the subject from the camera position). This type of reading is subject to error to the extent that different subjects have different rates of reflectance and the meter can only deal with an assumed average. You would do this if you were prevented physically from placing the meter w/diffuser at the subject position or in the same light as the subject.

Joe

 

[oceanbeast]

Use a hand incident meter to measure the light at the subject position with the dome pointed back toward the camera. If you can't place the meter at the subject position then place the meter in the same light as the subject and again point the dome toward the camera.

Your understanding about using the meter with a backlit subject is correct. Yes that would in most, or more likely all, cases overexpose the sky. If you reduce exposure so as not to overexpose the sky you will then underexpose the subject. There is no exposure that get's them both right -- pick your mistake or correct your mistake by altering the lighting contrast. The meter doesn't fix bad light.

If you remove the diffuser you can use the meter to take a reflected light reading of the light bouncing off the subject (point meter without diffuser at the subject from the camera position). This type of reading is subject to error to the extent that different subjects have different rates of reflectance and the meter can only deal with an assumed average. You would do this if you were prevented physically from placing the meter w/diffuser at the subject position or in the same light as the subject.

Joe

Joe,

Thanks for that detailed explanation. It was extremely informative. I do however have a follow up question, I am using this meter for landscapes hence I can not fix the lighting. Is it preferable on film to overexpose the sky and then try to burn it back in?

 

[dxqcanada]

Ok to over-expose negative (print) film, don't do it with positive (slide) film.
To what extent varies with the specific film.

Over exposure creates denser areas on the negative so it can be dodged during printing and still have detail. Under exposed areas are void of detail so burning cannot bring back anything.

Video on lightmetering: Measuring and Evaluating Light in Landscape Photography

 

[timor]

Hi Joe.
The problem with over exposing the sky in landscape photography lies not in the fact, that sky is sooo much brighter, then the rest of the scene, but in fact, that sky emits a lot of invisible blue light to which b&w film is very sensitive. To cut off this blue light you should use filters: yellow and orange, in some cases red for very strong sky. You might also use graduate ND filers. There is also polarizing filter.
As for measuring the light with incident meter for landscape it is easy. As incident meter basically is a very refine version of "sunny 16" rule you should take just general reading by rising your meter above your head with the dome in direction of incoming light. If the sun is not directly behind you, you may also take second reading directing the white dome towards the sun and compare. Of course this has limitations; you may shoot from a shadow, you may shoot against the sun etc. That is something you have to deal on the spot as condition vary, or, you may invest in spot meter, an instrument which basically 95% of landscape photographers have in some form (hand held or "in camera").

 

[dxqcanada]

Some B&W film have lower/balanced blue sensitivity ... like Fuji Acros 100
Rollei 80S has lowest sensitivity in the 400-500nm range.

 

[Ysarex]

Use a hand incident meter to measure the light at the subject position with the dome pointed back toward the camera. If you can't place the meter at the subject position then place the meter in the same light as the subject and again point the dome toward the camera.

Your understanding about using the meter with a backlit subject is correct. Yes that would in most, or more likely all, cases overexpose the sky. If you reduce exposure so as not to overexpose the sky you will then underexpose the subject. There is no exposure that get's them both right -- pick your mistake or correct your mistake by altering the lighting contrast. The meter doesn't fix bad light.

If you remove the diffuser you can use the meter to take a reflected light reading of the light bouncing off the subject (point meter without diffuser at the subject from the camera position). This type of reading is subject to error to the extent that different subjects have different rates of reflectance and the meter can only deal with an assumed average. You would do this if you were prevented physically from placing the meter w/diffuser at the subject position or in the same light as the subject.

Joe

Joe,

Thanks for that detailed explanation. It was extremely informative. I do however have a follow up question, I am using this meter for landscapes hence I can not fix the lighting. Is it preferable on film to overexpose the sky and then try to burn it back in?

This is a classic problem. On sunny days the contrast range increases as the light moves to the side and then eventually becomes backlighting. With transparency film you either fix the light or photograph something else. With color negative film you have some room to try and burn down hot highlights when printing. If it's a landscape sky that you're trying to burn you're success will have a lot to do with the character of the horizon (flat ocean versus trees and mountains). With B&W negative film you use the Zone System first and then burning while printing to supplement that.

An option while taking the photo is to use a graduated ND filter which may or may not be useful depending on the character of the horizon.

If you're going to work hybrid (film/scanner) then you have additional options that involve combining multiple scans to balance the tone response.

I know you're shooting a film camera, but another option is to use a high-bit-depth digital camera and use tone mapping or masking in post process.

Joe

 

[oceanbeast]

I am currently using a yellow 15 and CPL to darken the skies and give me some leeway with processing, I will develop my first roll tomorrow and for the most part I have been doing what you guys are saying so hopefully they turn out well exposed.

Thanks for the video. I do need a spot meter and have a digital camera but it's so cumbersome to carry around another body only for light readings and spot meters are prohibitively expensive to me right now.

 

[oceanbeast]

update - looks like you really cant go wrong using the light meter, all my exposures were pretty close to what I envisioned and with proper printing they should be right on. Moral of the story trust the light meter. However I can see how a light meter in much more capable hands can be used to create exceptional images. This is a learning process that might never end, now I can begin to explore the zone system a little.

 

[Ysarex]

update - looks like you really cant go wrong using the light meter, all my exposures were pretty close to what I envisioned and with proper printing they should be right on. Moral of the story trust the light meter. However I can see how a light meter in much more capable hands can be used to create exceptional images. This is a learning process that might never end, now I can begin to explore the zone system a little.

To explore the Zone System you'll need a spot meter. An incident meter gives you the correct exposure assuming that your scene contrast is a good match to the default tone response characteristics of your film. An incident meter does not provide a method to measure that scene contrast and so it's up to you to pass judgement based on your experience and ability to make an evaluation. A spot meter provides a means to actually measure the scene contrast and so validate the incident meter reading or begin the process of deviating from that incident exposure in conjunction with compensatory alterations in film processing both designed to better handle a scene contrast range that is not a good match to the default response characteristics of your film. Going back to your original post and concern for backlight: The Zone System further assumes that you are physically unable to fix the lighting which always provides a superior result and should always be your solution of choice. That assumption given you use the Zone System as a next best alternative to still get a passable photograph.

Joe

 

[Helen B]

If you do want to try a version of the Zone System that uses an incident meter to estimate scene brightness range (by measuring the illumination range and then estimating the brightness range by using the typical realistic reflectance range) then you could read Minor White's Zone System Manual or anything that refers to Beyond the Zone System. Both of these address the use of the Zone System with incident measurements. There are both advantages and disadvantages of using incident metering in this way.

Side note: If you ever compare the spectral response of films, be aware that there are two distinct methods of producing the graphs, and they give very different curves. Kodak use radiant energy for the y-axis, most other manufacturers use a simple wedhe spectrogram taken in tungsten light. That makes the red end look more sensitive than the energy method, and the blue end less sensitive than the energy method. It is very misleading, especially at the blue and UV end.

 

[hirejn]

If you have a backlit subject and expose for detail in the subject, the sky will always be blown out. That has nothing to do with how you meter. It's the principle of dynamic range. If you want to maintain detail in the sky and subject, you need fill light, HDR or some monstrous scrim. In general, always leave the dome diffuser on. When you need to meter the light falling on the scene, leave the dome out. If the dome also goes in, that's for when you need to measure a specific directional light. I don't know what your meter looks like with the dome off. Maybe there's a specific function for that. But I use Sekonic, as do most pros, and you generally leave the dome on and just turn it in or out depending on how directional the light reading must be. The only time I take the dome off is to clean the sensor.