Film plane metering with handheld meter

[steve_yeatts]

I'm new to LF. I'd like to take some extreme close-ups without

having to calculate exposure adjustments due to bellows extension.

Is it possibly to meter at the film plane using a regular hand-held

light meter? I was thinking that I could remove the back, and under

the dark cloth simply hold the meter at the film plane. If I did

this, I know I'd have to adjust for the fact that the light hitting

the meter would already reflect apeture and shutter speed settings,

but I don't know how to do this. Is this practical? Thanks.

[michael_briggs2]

<p>There have been special meters made to meter in front of the ground glass, and other meters have attachments to meter the light from the ground glass image. Another recent thread discusses these: <i>Meter reading on ground glass?</i> at <a href="http://www.photo.net/bboard/q-and-a-fetch-msg?msg_id=00AqP6">http://www.photo.net/bboard/q-and-a-fetch-msg?msg_id=00AqP6</a>.</p>

[mark feldstein]

Hi Steve: I contributed to that thread Michael referred you to. As I said there, the answer to your question is no, although there are some very expensive spot meter attachments available that allow you to meter ahead of the ground glass, or back attachments used in lieu of your ground glass with spot meter attachments.

 

As far as bellows factors, there is a gizmo available from Calumet, I think, that's basically a two-part scale printed on plastic. You place one scale. Find it on the ground glass, then use the other part to measure the size of that scale as it appears on the ground glass. That measurement gives you the bellows factor. Accurate? Well, it gives you ballpark factors. I still calculate them the old fashioned way by measuring how far I've got them racked out, and roughly how much swing, tilt and rise I've got for whatever lens I'm using. After awhile, you get pretty good at estimating the amount of compensation you need and a quick Polaroid tells you how much to adjust in order to zero it in.

Take it light.

Mark

[mark feldstein]

Sorry, my previous note got away from me before I could check it. I meant to say place the scale in the scene, then look for it on the ground glass and measure that one with the other part the scale. The chart they provide gives you the bellows factor from that reading.

Mark

[ronald_moravec1]

Tha gadget from Calumet works. Alturnatively you may set the camera up for infinity focus and then aim it at a evenly lit white board. Take a reading off the glass with a flat diffuser on an incident meter. Cover with dark cloth for the reading. Then focus on a 16x20 target and take another reading. Same for 8x10 and 4x5.

 

2x2 1/2 perhaps 4 stops extra

 

4x5 should require two extra stops from infinity reading

 

8x10 one extra

 

16x20 1/2 extra.

 

These will not be correct readings, but will give you the correction factors to apply to an incident reading at the subject plane. The correction factors can be applied to gg to lens board distance or subject size, whatever is easier for you to work with.

 

If you are having sensitivity problems with the meter, do infinity at 22 and open the lens for the other distances and see how far you must open to get the same reading for the other subject sizes.

 

1:1 is always 2 stops with a symetrical lens, although 1:1 is a different subject size with different formats.

 

I have not done this in a while, so the 8x10 and 16x20 corrections may be off a little, but the ratios remain the same across all formats for 1:1, 1:2 1:4 etc. Symetrical lenses only! You may establish corrections for a tele lens this way, but can not apply it to other symetrical lenses.

 

Search the net for bellows correction factors for more detailed explanations.

[capocheny]

Steve,

 

Sinar use to make a film-like cassette that would insert into the back of your v/c (like

a regular film holder.) This cassette accepted a metering probe that's attached onto a

meter. I believe they're still made by Sinar and is very effective.

 

Alternatively, Minolta use to make a probe that was used to measure light falling onto

the groundglass. All you had to do was to calibrate it according to their set of

instructions.

 

Lastly, as Mark has discussed (and this is what I've been using), the Calumet device is

very useful for what you want to do. There use to be a free version, which you could

print out buy I'm not sure where it's located. Perhaps someone else on this forum can

jump in with the link.

 

Good luck.

 

Cheers

[davidv1]

Here's a free calculator. The PDF is at the bottom of the page.

 

http://www.southbristolviews.com/pics/Graphic/CloseUpCalc.html

[davidv1]

And another one.

 

http://salzgeber.at/disc/index.html

[john lehman, college alask]

I use a regular meter (a Gossen Luna Pro digital) with a 1/3 stop compensation using the techniques described in Baker's _Field Photography_. While I (and I suspect most of the scientists who used Baker as a textbook for decades) have found that this technique works very well, even for slides, the Photonet consensus from previous discussions has been that it is impossible, since it doesn't use expensive special purpose equipment.

 

Basically, you set the meter for somewhere between f/1 and f/1.4 and read the exposure time.