Jump to content

Large Format Focal Plane Metering


davidgooding

Recommended Posts

Hi All,

 

It's been quite a few years since I was last on here.

 

I'm not actually a photographer! I don't have the artistic skill necessary for that and am an engineer by trade and nature instead.

 

A few years ago I made a post here about whether a low-cost focal-plane metering system for large format cameras would be a useful product, after having developed one for my father (he has a Sinar P), and I got quite a bit of positive response and helpful suggestions.

 

After that, life got in the way and I did nothing much further with it. However, more recently, after having refined the design and providing a few more for large format photography hobbyists (and developing it further each time with their input), I have decided to take this further. I have therefore put in some effort over the past year to productionise the design, have produced a production batch, and am now taking steps towards marketing it.

 

Basically it consists of a metering frame, which is inserted in place of the film carrier, which contains a metering probe which can be moved around the image to meter at specific points in the image. There's a picture below to give the general idea.

 

At the time I originally started this, there were other meters of a similar concept on the market but at prices that were out of reach of many. The aim here was to produce a more basic, but still accurate, useful and reliable, meter at a much more affordable price.

 

Do people consider that this is a useful product, and one which people would seriously consider at the price point I can achieve (£120, or roughly US$160, or Euro 140)?

 

Are there any suggestions, questions or comments on the design?

 

Do significant numbers of people still use film anyway?

 

I have put it up on the internet here if anyone is interested in taking a closer look - www.dlgelectronics.com. I'll go further with this if people think it worthwhile.

 

I would also be interested in developing further products if (1) this proves at least moderately successful and/or (2) anybody has any ideas or requirements for similar things.

IMG_0224.JPG.c3bcc29e4a27f11320095115e435b618.JPG

 

Thanks for your interest!

 

Dave

Link to comment
Share on other sites

Did you check to see if that metering frame and probe are covered by patents from Sinar or Gossen?

Thanks for your input. I did do a patent search and I am not infringing any patents that I know of. However I'll run some more specific searches for Sinar and Gossen.

This unit does not have a special metering back for the camera (unlike the Sinar meter) but instead is a relatively cheap and cheerful thing using a frame that inserts in place of the film carrier with dimensions compatible with a standard film carrier. This frame accommodates a moveable metering probe through a slot in the top. The price you pay for this is a slight defocussing of the image while you are metering due to the rearward movement of the ground glass when the frame is inserted, approx 9mm.

Link to comment
Share on other sites

  • 2 weeks later...

IIRC, this looks exactly like the Sinarsix; a modified Gossen Lunarsix with an external CdS probe that slotted into the camera back.

 

It had issues of its metering being rendered inaccurate by light coming through the viewing screen and affecting the meter sensor. Beside which, its spot-metering character required quite a lot of experience to use effectively.

 

This sort of meter only comes into its own at close focus where bellows draw is an issue, and as such the chances are high that flash will be used for lighting. If it can't meter flash, then it's of limited use.

 

A handheld incident/reflective meter proved much more accurate in practise IME, provided one made allowance for bellows extension. And that's not difficult by simply multiplying the marked aperture by the factor of (actual bellows length/infinity bellows draw) to give the effective aperture.

Link to comment
Share on other sites

I bought the Gossen thing back in the day. I absolutely agree with Joe above about spot metering wisely being a challenge. - The work around was the old Linhof metering and focusing bellows where you had a plastic funnel to stick your Lunasix behind it's diopter and meter the entire ground glass. Since you already built a modular meter I guess providing another metering sensor with attached cable and an option to adjust it for metering the entire groundglass or a whole lot of it shouldn't be complicated?

I guess I would buy your construction (or kit?), if I had nothing (and if it does indeed meter flash too).

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
×
×
  • Create New...