math in photo? nooooooo

[Fate]

lol thats awsome hertz..... but it went straight over my head

 

[DocFrankenstein]

Their shpellings and maths are not needed at all

 

[Christie Photo]

Bellows is to do with close-up work ....Actual exposure time=metered exposure x bellows extension squared/focal length squared

I can say all that in my sleep

Yeah! I KNEW you'd have it. Isn't funny how those things stick with ya?

You get a big "atta boy!"

 

[Don Simon]

My extension tubes only just arrived today, and since reading that last bit I'm now looking at them in abject terror. Curse you Hertz!

 

[Dave_D]

When I use a bellows I will borrow someone's digital body, take a shot and adjust for the exposure I want. When I have it, I get rid of the digital body and put the "real" camera on and shoot away.:lmao:

 

[Unimaxium]

Bellows is to do with close-up work - usually with 5x4/10x8 but you can get it with extension tubes.
Exposure meters and f-stops work on the principle that the image is formed one focal length behind the lens. Approximately true for normal circumstances.
When you focus on an object near to the lens the image is formed much further back behind the lens. The inverse square law means that the image will be much dimmer and so the exposure will be wrong.
An object at 2 focal lengths from the lens will therefore produce an image 1/4 as bright as the indicated exposure.
Bellows factor allows you to compensate for this effect.

Actual exposure time=metered exposure x bellows extension squared/focal length squared

I can say all that in my sleep

I'm a little confused. I understand how with e.g. an extension tube the image projected onto the film/sensor will be dimmer than if you use the lens at its native focal length(s). But I don't get how the exposure will be off if you are using a camera with TTL metering. If the lens is projecting a dimmer image, wouldn't the meter just read for a longer/wider exposure? Or am I missing the point?

 

[Hertz van Rental]

If you have TTL then it would compensate.
Bellows comes from the good old days of manual studio cameras. It's useful for large format work if you don't have a built-in meter - and not a lot of 5x4 or 10x8 cameras do.

 

[Unimaxium]

Ah, ok. I guess I was just confused what kinds of cameras you were talking about.

 

[Lumix]

Can I just SUM UP, if you will excuse the pun, In 52 years of photography I've calculated that you only need two things. One good eye and a quick finger.

 

[Rob]

One good eye and a quick finger.

And a camera... assuming you were talking photography of course

 

[doenoe]

film or memory card would be nice to.

 

[Lumix]

Rob, that's the army's philosophy, and it holds good in photography aswell.

 

[Rob]

They don't like it up 'em, Captain Mainwaring Sir!

 

[Don Simon]

And although no doubt a finger and an eye can be deadly, surely some kind of weapon would also be useful?

Welcome to the Pedants' Society AGM :mrgreen:

 

[Hertz van Rental]

They don't like it up 'em, Captain Mainwaring Sir!

:lmao: As you were, Lance Corporal Jones.