Working out exposure times for pinhole hybrid

kristelt · Mar 23, 2023

Hey, Hope everyone's keeping well.
I've found this forum really useful and hoping I can get some advice on this.

I have built another box camera hybrid and need to work out the exposure times. I have a hand held light meter, but can't seem to get the focal ratio right somehow.

Im using a lens with a built in shutter and apertures 8 and 16 Im mostly sticking to.

Am I right in thinking that I need to divide the focal length of the camera (ex.210) by the aperture (8) ?

Any advice would be much appreciated.

{Moderator's edit: readers of this thread may find it useful to know that it appears to be in reference to a lens camera using an extremely small aperture, rather than a classically defined "pinhole"|

BradS · Mar 23, 2023

the f-number or, focal ratio, is simply the distance from the pinhole to the film divided by the diameter of the pinhole.
so, for example, if your focal length is 210mm and the diameter of the pinhole is, 0.7mm then the f-number is:

210 / 0.7 = 300

BradS · Mar 23, 2023

or are you using a lens?
if using a lens the focal ratio is still the focal length divided by the diameter of the entrance pupil of the lens.
so look into the front of the lens and estimate the diameter of the aperture....looking through the lens.

wiltw · Mar 23, 2023

The intracacy of f/number calculation lies in the difference between a 'simple' optic and a 'complex' one. Most manufactured photographic optics consist of multiple optical elements and are 'complex'.

reddesert · Mar 24, 2023

Even when an optical system is complex, the f-number is given as BradS said, the focal length divided by the entrance pupil diameter - the entrance pupil is the apparent aperture diameter as viewed through the front of the lens (not the mechanical diameter of the aperture).

kristelt · Mar 24, 2023

Okay, thanks for your messages. Maybe I should have framed it "Working out exposure times for a pinhole hybrid"
I have a hand held light meter and cant seem to get it right, which was making me question that my focal ratio was correct.

The lens I am using is a carl Zeiss Jena f 16.5 (its a simple lens)
The shutter options range from 1sec to 200th
Apertures I've been sticking to are 8 or 16

kristelt · Mar 24, 2023

BradS said:
or are you using a lens?
if using a lens the focal ratio is still the focal length divided by the diameter of the entrance pupil of the lens.
so look into the front of the lens and estimate the diameter of the aperture....looking through the lens.

Thankyou...Its what I tried, but I had a day of test shots and no consistent results. Perhaps there are other underlying issues that need to be ironed out.

grain elevator · Mar 24, 2023

kristelt said:
The lens I am using is a carl Zeiss Jena f 16.5 (its a simple lens)
The shutter options range from 1sec to 200th
Apertures I've been sticking to are 8 or 16

Wait, what is pinholey about this? You're using a lens! Are you saying it's a 16,5 cm (not f/16.5) lens? You just also stated the apertures you used, so what are you trying to calculate?

Maybe coming from pinhole you're used to having to do calculations, with a lens you have your f/numbers stated on the lens/shutter, you don't need to calculate them. Or does your shutter not belong to the lens and you question the aperture markings on it?

BrianShaw · Mar 24, 2023

It might help further the discussion if we understood what camera is being discussed. I’ve been puzzled for about a year! See post 4. “Pinhole” and “hybrid” might be used differently than we normally use those terms.

Is stop necessary for a paper negative?

Hello, Im creating a pinhole hybrid camera...that uses paper negatives. I'm just wondering if I could get advice from anyone on whether a Stop bath..for a paper negative is even necessary? I've read that an acidic fixer means you don't need one. Just want to make sure it doesn't effect the...

www.photrio.com

nmp · Mar 24, 2023

BrianShaw said:
It might help further the discussion if we understood what camera is being discussed. I’ve been puzzled for about a year! See post 4. “Pinhole” and “hybrid” might be used differently than we normally use those terms.

Is stop necessary for a paper negative?

Hello, Im creating a pinhole hybrid camera...that uses paper negatives. I'm just wondering if I could get advice from anyone on whether a Stop bath..for a paper negative is even necessary? I've read that an acidic fixer means you don't need one. Just want to make sure it doesn't effect the...

www.photrio.com

As I understand, hybrid pinhole uses a simple lens with an attached aperture whose diameter is close to a pinhole's. So in a way it is a regular lens camera with really, really high f number.

:Niranjan.

BrianShaw · Mar 24, 2023

Well that sounds rather standard to me!

… then aside the possibility of a knowledge gap of basic photographic exposure principles and practices, I don’t understand the question/problem. Perhaps how to time a long exposure or reciprocity failure impacts?. IDK.

I’m hoping that @krisfelt will clarify!

xkaes · Mar 24, 2023

You do not use a pinhole on a lens. It's either a pinhole or a lens -- not both.

Ian C · Mar 24, 2023

I think that kristelt is refering to a Carl Zeiss Jenna Tessar f/4.5 f = 16.5 cm lens.

If so, then in standard language, it’s a 165 mm f/4.5 Zeiss Tessar. Hopefully he will clarify this so that we can address his question.

We need to know the shutter speed and aperture ranges available. It seems likely that this has nothing to do with a pinhole camera. It would also be useful to know the make and model of light meter used for measuring the light. Likewise, is this camera using film, or is it using photo enlarging paper to record the exposure?

A pinhole camera uses a pinhole to form the image. It has NO LENS. If the image is formed by a lens, then it isn’t pinhole camera, regardless of the aperture size and whether the lens has a variable-aperture iris unit or some sort of jury-rigged waterhouse stop.

grain elevator · Mar 24, 2023

Ian C said:
f/4.5 f = 16.5 cm lens.

Right, I just realised f/ and f= must be confusing for someone not well versed in the lingo/principles behind this.

xkaes · Mar 24, 2023

Let's add in f: to confuse things even more.

We should probably stop guessing what kristelt is trying to do -- although I know we won't.

BrianShaw · Mar 24, 2023

grain elevator said:
Right, I just realised f/ and f= must be confusing for someone not well versed in the lingo/principles behind this.

xkaes said:
Let's add in f: to confuse things even more.

We should probably stop guessing what kristelt is trying to do -- although I know we won't.

If the lens is indeed as Ian C guesses and krisflet seems to imply...

and how about that comma; 16,5 versus 16.5 cm always seems to confuse me. And converting to mm or inches... wow, more confusion!

(image from ebay and used for educational and demonstrative purposes only (fair use)

nmp · Mar 24, 2023

This might explain the confusion:

MattKing · Mar 24, 2023

In any case, this thread clearly doesn't involve any sort of "hybrid" as it is referred to in the Photrio sub-forum organization, so I'm moving it to the Miscellaneous Equipment sub-forum, and then adding the following explanation to the OP's first post: {Moderator's edit: readers of this thread may find it useful to know that it appears to be in reference to a lens camera using an extremely small aperture, rather than a classically defined "pinhole"|

BrianShaw · Mar 24, 2023

Taht was really informative and educational... I did not realize that there was a lost tribe of masonites.

BradS · Mar 24, 2023

The guy in the video is talking about a 150mm glass lens with a 3mm stop ( ==> f/50). He keeps saying "hybrid pinhole" but this is a glass lens. It has nothing to do with pinhole. Extreme confusion.

BradS · Mar 24, 2023

kristelt said:
Thank you...Its what I tried, but I had a day of test shots and no consistent results. Perhaps there are other underlying issues that need to be ironed out.

No problem.
I'm kinda confused about what you are doing and what you are using.

Please confirm the following:

using a glass lens with focal length = 16.5 mm ?
exposing paper? or film?
what film speed (ISO/ EI) are you using ?
making the exposure in daylight?
using an aperture of f/16 ?

your question is what shutter speed to use?

Are you aware of the "Sunny-16" guideline for exposure estimation?

kristelt · Mar 28, 2023

BradS said:
No problem.
I'm kinda confused about what you are doing and what you are using.

Please confirm the following:

using a glass lens with focal length = 16.5 mm ?
exposing paper? or film?
what film speed (ISO/ EI) are you using ?
making the exposure in daylight?
using an aperture of f/16 ?

your question is what shutter speed to use?

Are you aware of the "Sunny-16" guideline for exposure estimation?

Hello,
Part confusion probably is I started off using pinhole and am now using a glass lens.
Im using a glass lens with the focal length 16.5
exposing a paper negative
Most paper has been 100 ISO (currently just ordered some with no ISO number written on it)
Making exposure in daylight
using aperture f/16 or f/8

My question is what shutter speed to use with my hand held light meter? (So far not consistent, which made me feel I was getting things wrong)...

Wasn't aware of the sunny 16 guideline, this is all fairly new to me, so thanks for that too..

BrianShaw · Mar 28, 2023

You seem to be struggling with photographic exposure and a fundamental misunderstanding of ISO speed may be a problem. Film and paper ISO speeds are not the same.

You might want to review some basics from a reliable source. Scroll down to the pinhole section where using paper negatives is discussed.

Starting out and Pinhole photography FAQ'S

Your first point of call for all Frequently Asked Questions relating to getting started in film photography and pinhole photography

www.ilfordphoto.com

kristelt · Mar 28, 2023

BrianShaw said:
You seem to be struggling with photographic exposure and a fundamental misunderstanding of ISO speed may be a problem. Film and paper ISO speeds are not the same.

“Paper and film ISO speed work in different ways. As an approximation use a film ISO speed of 3-6 for our Multigrade papers but this may vary with the product and types of exposure. You may need to find your optimum value through trial and error.”

You might want to review some basics from a reliable source. Scroll down to the pinhole section where using paper negatives is discussed.

Starting out and Pinhole photography FAQ'S

Your first point of call for all Frequently Asked Questions relating to getting started in film photography and pinhole photography

www.ilfordphoto.com

Thats great..I'll take a look . Many thanks.

BrianShaw · Mar 28, 2023

Understanding Exposure, Part 1: The Exposure Triangle

Photography is all about capturing light. In fact, the etymology of the word “photograph” is basically “light drawing.” To make a photograph that we can see, we have to control both the amount of light that is exposed to a photosensitive surface, be it film or a digital sensor, and also control...

www.bhphotovideo.com

Working out exposure times for pinhole hybrid

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