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smithdoor
5-Nov-2013, 16:18
If you need Bellows Exposure calculation down load with filter calculation
Try this wheel for calculations

Dave

StoneNYC
5-Nov-2013, 17:41
The reciprocity timer app for iPhone does all that for you, it's really great and was developed by a LFF member :)

Check it out on the App Store

https://itunes.apple.com/us/app/reciprocity-timer/id459691262?mt=8

104144

Steve Sherman
5-Nov-2013, 19:23
Bellows Extension factors need not be nearly as confusing as some suggest.

Placing a known object in the zone of critical focus and then taking a measurement on the ground glass of that object with a unique measurement devise can seem quite daunting.

For years I've used a very simple method to calculate bellows extension compensation, and it's all in your head.

Example, 210mm lens, also known as a 8 1/4" lens ( this measurement is @ infinity ) Convert the length of the lens ( in inches) to an F stop, i.e. 210mm = F 8, if your bellows extension is measured at 11 inches then you allow 1 stop additional exposure, F 8 to F 11 = 1 F Stop, if measured at 14" then allow 1.5 stop increase in exposure.

210mm (8 1/4" ) lens extended to 16" is just slightly lens than 2 full F Stops. BTW, any size lens extended X 2 is life size, i.e. 6" lens extended to 12" or 10" lens extended to 20" produces a life size image on the ground glass and always dictates a 2 stop increase in exposure.

Some may say this method is not accurate enough, for years I did product / table top photography with box specific ISO Ektachrome film and rarely missed a bellows calculation.

Cheers

StoneNYC
5-Nov-2013, 20:02
Bellows Extension factors need not be nearly as confusing as some suggest.

Placing a known object in the zone of critical focus and then taking a measurement on the ground glass of that object with a unique measurement devise can seem quite daunting.

For years I've used a very simple method to calculate bellows extension compensation, and it's all in your head.

Example, 210mm lens, also known as a 8 1/4" lens ( this measurement is @ infinity ) Convert the length of the lens ( in inches) to an F stop, i.e. 210mm = F 8, if your bellows extension is measured at 11 inches then you allow 1 stop additional exposure, F 8 to F 11 = 1 F Stop, if measured at 14" then allow 1.5 stop increase in exposure.

210mm (8 1/4" ) lens extended to 16" is just slightly lens than 2 full F Stops. BTW, any size lens extended X 2 is life size, i.e. 6" lens extended to 12" or 10" lens extended to 20" produces a life size image on the ground glass and always dictates a 2 stop increase in exposure.

Some may say this method is not accurate enough, for years I did product / table top photography with box specific ISO Ektachrome film and rarely missed a bellows calculation.

Cheers

I'm lost, this is not at all easy, especially if you don't know how to convert mm to inches in your head... Why can't you keep it at mm's?

cowanw
5-Nov-2013, 20:14
Of course you can; as long as you know how many stops are between f210 and f420.
There are as many ways to learn this as there are learners.
Smithdoor's wheel is another good way.
As always, the best is to understand the principles and then you can understand why they all work.

StoneNYC
5-Nov-2013, 20:19
Of course you can; as long as you know how many stops are between f210 and f420.
There are as many ways to learn this as there are learners.
Smithdoor's wheel is another good way.
As always, the best is to understand the principles and then you can understand why they all work.

I think I'll stick to the app haha and version 2 is coming out soon with zone mapping and notes and goodies. Lol

Steve Sherman
6-Nov-2013, 04:45
I'm lost, this is not at all easy, especially if you don't know how to convert mm to inches in your head... Why can't you keep it at mm's?

25mm = 1 Inch Always several means to an end

Cheers!!

smithdoor
6-Nov-2013, 07:14
1" = 25.4 mm it was round off
here one for you 1 m is close to 1 yd+ or ( 1m = 39.37" or 3' 3.37" or 1.09 yds)

Dave

25mm = 1 Inch Always several means to an end

Cheers!!

Drew Bedo
7-Nov-2013, 08:33
I have pre-calculted the correction for my two most used lenses, 150mm and 210mm.

When in the field, I compose and focus, then measure the total amount of extension. For the 150 (6 inches, right) each inch beyond infinity is one third of a stop extra exposure.

For the 210mm (8.25 inches) the correction that I use is one quarter of a stop extra exposure for each inch beyond infinity.

To each his own: You can make this as complicated as you want. There are many threads on this topic and many methods—some with formulas (Ok: So what if the plural is "formulae).

Try out a few ways and settle on what works for you.

Kirk Gittings
7-Nov-2013, 08:40
http://www.salzgeber.at/disc/disc.pdf

I use this simple tool. It works fine and I don't have to use my math challenged brain.

BrianShaw
7-Nov-2013, 08:50
I use this simple tool. It works fine and I don't have to use my math challenged brain.

et tu Brute?

Kirk Gittings
7-Nov-2013, 09:43
et tu Brute?

:)

smithdoor
7-Nov-2013, 12:23
I have upload a APERTURE / SHUTTER SPEED Exposure Factor Chart and if you are use just a 135mm lens a Bellows exposur factor

Dave

Jim Becia
7-Nov-2013, 13:17
http://www.salzgeber.at/disc/disc.pdf

I use this simple tool. It works fine and I don't have to use my math challenged brain.

I use this also and have about 3 or 4 sets of the disc in every large format camera bag I own. They have been washed away and blown way, so having a few extras on hand works out well. Have also given a number of them away to LF guys who were not aware of bellows extension calculations. Seeing that I don't carry any other type of measuring device, this has worked perfectly for all formats when it comes to close focusing and bellows extension.

Mark Sawyer
7-Nov-2013, 13:45
I never figure bellows extension. I just figure out what the f/stop is. Focal length divided by aperture. No discs, no apps, no conversions...

Come on, guys, it's just a ratio...

smithdoor
7-Nov-2013, 13:59
The basic on Bellows Exposure calculations is if you more than 6' for lens under 100mm no change if you lens is 150mm then more 12' no change only if you are working close will make change in exposure setting. Most of the time I working over 12' with a 135mm and do not make changes

Dave

I never figure bellows extension. I just figure out what the f/stop is. Focal length divided by aperture. No discs, no apps, no conversions...

Come on, guys, it's just a ratio...