Calculating exposure for close ups

[thegman]

Hello,
I just shot my first 4 shots of 4x5 film, and sent it off for development. I took 3 shots of distant subjects (i.e. 50 feet away). As I understand it, no bellows factor compensation is required for that?

I took one shot as a close up, the subject was perhaps 2 feet away from the camera. That means I should have (but did not) apply any compensation for the fact that my bellows were a fair bit extended. I did a 1 stop over exposure anyway, as I that is what I tend to do anyway, but presumably I should have applied compensation?

I've seen many formulas online for working this out, but I wonder could it also be as simple as metering off the ground glass? i.e. if I just put my VC II meter up against the ground glass, and meter from that? Would that in effect be TTL metering? Or am I missing something obvious?

Thanks

Garry

 

[Brian Legge]

I haven't heard of that approach before. Interesting idea.

You could test this by metering a scene and then metering off the glass. See if their is a common factor (ie the glass is always N stops less or the glass is always 1/N EV of the scene).

If so, you could probably run with that as your metering approach.

 

[thegman]

Thanks Brian,
I'll give it a go when I get home. I think I'm OK for scenes which don't require bellows compensation, but the whole bellows thing throws my Sunny/16 guesstimation approach out the window...

Garry

 

[Roger Hicks]

You can (sort of) do it -- there's even a 'metering cassette' attachment for some Gossen meters -- but it'll require (1) a good heavy dark-cloth; (2) compensation for where on the screen you meter (light loss through the ground glass -- hence the 'cassette') and (3) wasting a fair amount of time and possibly materials.

A significantly easier approach is remembering that double extension or life size (e.g. 400mm of bellows with a 200mm lens) requires two extra stops, while 150% extension or half life size (300mm with a 200mm lens) requires one extra stop. Quarter life size (250mm) needs half a stop. Interpolate from these: you'll be close enough with neg film, especially if you take care always to err on the side of overexposure.

Cheers,

R.

 

[thegman]

Thank you Roger, I think I was at about 300mm of bellows on a 150mm lens, and over exposed by 1 stop, so I guess in reality, I underexposed by 1 stop, which I guess is probably not going to look too awful. It was just test shot of some flowers anyway, just learning the ropes.

 

[mbisc]

There is a quick & dirty (but very accurate) rule of thumb. Take the focal length of your lens in inches (say, a 210mm lens, which would be 8 inches), and measure the lens-to-film distance after focusing (say, 11 inches). Then "translate" this into f stops: f8 to f11 -- that's one stop of compensation for bellows extension.

 

[thegman]

There is a quick & dirty (but very accurate) rule of thumb. Take the focal length of your lens in inches (say, a 210mm lens, which would be 8 inches), and measure the lens-to-film distance after focusing (say, 11 inches). Then "translate" this into f stops: f8 to f11 -- that's one stop of compensation for bellows extension.

OK, that's an interesting and simple way to work it out. Most of my shots will likely be at infinity or close to it, so generally I won't need to worry too much about it.

 

[mbisc]

OK, that's an interesting and simple way to work it out. Most of my shots will likely be at infinity or close to it, so generally I won't need to worry too much about it.

Exactly -- at/near infinity, you don't have to worry about bellows extension compensation.

 

[Jerevan]

I just use this: http://www.salzgeber.at/disc/

 

[oftheherd]

I just use this: http://www.salzgeber.at/disc/

That's kind of neat. But I guess I am just old fashioned and prefer to measure and do the math. Sometimes us old fogies like to stick with what we learned long ago (in a far away land )

 

[Jerevan]

I suck at maths.

 

[Sanders McNew]

I shot a portrait series in 4x5 and 5x7 for several years. As
a practical matter, I think the whole "bellows compensation"
business is overblown, at least for the distances you will be
using in portraiture. (Maybe macro work would be different.)
My only caveat is that I always rated TXP (my film of choice
for LF work) at 160 instead of 320, and processed in Rodinal.
To the extent any light loss was occurring, it was well within
the tolerance of my exposure and processing.

It's easy to overthink this stuff and fetishize the rules. Just
expose and process a few sheets, and tune from there. If your
negatives seem a bit thin, it could be from "bellows effect," or
a fast shutter, or from your film EI, or from your developer
recipe, or from your water temperature, or who knows what?
The easy answer is to open up a stop, or choose a slower
shutter speed. Or use a faster film. Don't drive yourself
crazy trying to make a mathematical compensation for a
hypothetical effect.

I shot the attached photo through a 12-inch Commercial
Ektar. I used no bellows compensation in arriving at an
appropriate exposure for the frame.

 

[mbisc]

If your
negatives seem a bit thin, it could be from "bellows effect," or
a fast shutter, or from your film EI, or from your developer
recipe, or from your water temperature, or who knows what?

Well, I think the point here is that once you nailed down all these variables via film testing, then having bellows compansion issues isn't going to affect the consistency of your final negative.