Bronica GS-1 flash/hand-held meter exposures

[guyvickers]

Hi,

 

I have a GS-1 with 120 and 220 backs, waist level finder and two

lenses. I am going to be shooting people in their work environment

(outdoors) and need to know a few basics.

 

I have a gossen digisix light meter-is it just a case of taking a

reading at the person and using this value on the camera? (i.e white

plastic bulb (incident mode) toward camera). Or do I need to then

underexpose due to light coloured skin?

 

Secondly if I am to use flash as a fill, can I use my F280 Olympus

flash on the auto winder, have the flash fire at full output and then

use aperture to determine amount of fill. i.e use guide number/

distance to subject equals aperture. Or is there some rule about f8

on 35mm is not equal to f8 on 6x7? I Read that f8 on 6 x 7 has dof of

f4 in 35mm format.

 

Appreciate any advice from those who know this kind of stuff and have

had experience with it.

 

Kind Regards

Guy

[russ_britt1]

Fill flash is best done on a camera that will sync. with flash at any shutter speed. I don`t think you can do that with your Bronica. But you let the flash control your f-stop and the ambient light control you shutter speed ,untill you get the blance of flash/ambient light you want.

Example if flash output gives f8 at ten feet and you subject is ten feet away your fstop is f8. You then take a ambient reading at f8 and see what shutter speed you get. If the ambient reading calls for 1/60 of a second then f8 at 1/60 will balance the flash and ambient light at ten feet. If you want more ambient light in the picture you use a slower shutter speed and stop the lens down a stop. if you want more flash use a faster shutter speed.This is not as hard as it sounds.

[pavelp]

If you take incident reading, you shoot at the value that the meter shows (unless you have some other reason to compensate). You can try following experiment:

 

Take a reflected light reading of a completely white, evenly and well lit wall. Switch the meter to incident and take the reading right at the wall with the dome pointing to the light source. You should see about two stops difference between incident and reflected readings (the incident will tell you to open two more stops). Openning two stops is often recommended as a compensation for reflected light reading to expose the white color correctly. With incident reading colors do not come to play, only the intensity of the light source(s) illuminating the subject.

 

Regarding the flash, I would do it little differently. I would decide what lens I will use and from that how much DOF I will need. That gives me the aperture. Then using the guide number/aperture, I will get the distance of the flash from the subject. This requires off-camera flash, but gives me total control of exposure/DOF.

 

Or you can do it with on camera flash, but aperture will be determined by flash guide number and distance from the subject (so you cannot control the aperture).

 

Come to it, doesn't the Digisix have a flashmeter? I am using Luna Pro SBC (also Gossen) with Lunaflash module for flashmetering and nothing, nothing beats that in accuracy.

 

The DOF rule you mention is quite simplified. Normal lens for 6x7 is about 100mm (give a penny, take a penny). Normal lens for 35mm is 50mm. That's where the DOF difference comes from (longer focal length, less DOF). But that has nothing to do with aperture and so it will not affect your flash exposure.

[richard baznik]

Note that the GS-1 shutter can synch with flash at any speed. It's a leaf shutter. As Pavel indicates, you will still have to use the aperture necessary to give you the right exposure for the area to be filled-in with light, but you can alter the shutter speed to make the rest of the image look the way you want it to. Your other option is to pick a film whose speed will yield the aperture (and thus DOF) you want.

[guyvickers]

Thanks Russ,Pavel and Richard.

 

I have learnt a lot from your comments. My memory is refreshed about some flash reading done years ago. I have become reliant on TTL in 35mm format.

 

This is what I learnt, please make comment if you think necessary.

 

The incident mode on light meter measures accurately the exposure to use (i.e light skin is within the film latitude range and "medium" toned subjects will appear medium). Under or over exposing would only be necessary for creative effect. My Gossen Digisix is not a flash meter, only ambient and reflected.

 

I need to use 100 speed film (end-use reasons) for these upcoming outdoor people shots and always have flash on the camera (no assistant to hold flash closer to subject). Therefor I propose to use Russ's method of flash output decides aperture and ambient light determine shutter speed. My F280 Olympus flash has an effective Guide Number in outdoors of 16 (GN16/f8 = 2 metres distance to subject-this is accurate and proven with 100 iso).

 

So, if I took a sunny day,used f8 as an aperture (on my 80mm f3.5 PG Bronica), then the subject distance would be 2 metres and the correct shutter speed for a "normally" exposed background would be an equivalent of "sunny f16"-i.e f8 1/500. Perfect! This means I can hand-hold the GS-1 without fear of camera shake and then toggle these aperture/shutter settings to alter flash/background balance.

 

Last question-will my F280 be likely to fire on the GS-1 autowinder, or am I better to use a short PC cord and flash bracket (my OM flash does not have a PC socket)?

 

 

Last thought, re dof and medium format, understand that f8 on PG 80mm f3.5 will give me same dof as f8 on 40mm lens in 35mm format, yes?

Many thanks

 

Regards

Guy

[pavelp]

The incident mode on the meter measures the amount of incoming light without getting confused by the reflectance of your subject. If you take incident reading and shoot at measured value, white will be white, black will be black and gray will be gray. On the other hand, reflected light meter always assume that everything is 18% (or so) gray. So if you meter white, the meter will tell you to underexpose, because it wants the white to be gray. Same problem with black (but in this case the meter will tell you to overexpose). I believe the reason why the incident reading is not built into cameras is 1) you have to walk to your subject 2) you have to point the meter "the wrong way" (I get lots of snickers from general public when I take incident reading ("Uhmm, hello! We are here!")).<br><br>

 

Here's an <a href=http://www.dantestella.com/technical/fill.html>excellent article (by Dante Stella) on how to do fill flash</a>. <br><br>

 

I am not sure about how well the Olympus flash will work with the speed grip. GS-1 Speed Grip seems to have standard hot shoe with two added pins (most likely for Bronica Speedlite dedication). I've used nondedicated Promaster 5700 flash with the GS-1 using simple sync cord between the flash and the X-socket on the camera. It really depends on what is the show on the F280 (which I;ve never seen). But if all fails, the PC cord will work. <br><br>

 

f8 on PG 80mm will give you same DOF as f8 on any 80mm lens in 35mm format. DOF depends on the aperture and focal length, it has nothing to do with format. 80mm lens in 6x7 format will act like a very moderate wideangle while it is a slightly telephoto in 35mm format.But the DOF is same. BTW, I think the lens is actually 100mm/f3.5.

[guyvickers]

Thanks Pavel, great link to the flash info and think its now a case of getting out putting it into practice. Yes there is a Bronica 100mm f3.5 and an 80mm f3.5, I have read that the 80mm PG 3.5 is the "newer more corrected version with better coatings". I've only had it a few days so don't know the results yet.

 

Kind regards

Guy

[pavelp]

You're right. There really is a 80mm/3.5 lens for the GS-1. Interesting.