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## Applied Mathematics to Holga Cameras

### As I like to use science for good Lomographic reasons, let me present you the External Shot counter!

Sometimes, you cannot see the shot N° from the little window behind so I thought to make an external shot-counter. When you roll your film, you turn the wheel of a certain angle to fall on a correct shot position. This angle reduces as the diameter of the roll is increasing. Here, I used an empirical analysis (empirical means by experiment) to determine the good angles (more than 360° rotation before shot 12) needed to turn the wheel in order to make 12 separated shots on any film.

To make measurements of the wheel angles, I placed a white sticker on the wheel, used my Holga normally (by watching shot numbers in the little red magic window) and noted every position of every shot on the sticker. I did this for four films (Provia, Sensia, Velvia and a strange one I forgot the name). Then, I calculated a mean rotation angle over all films to obtain a mean measurement applicable to all films (I hope) by applying a third order polynomial regression. Finally, I produced an external shot counter with Photoshop, printed it, and stuck it on the Holga wheel. I tried it many times. IT WORKS.

As science is about sharing information, I put here a copy of the counter. Print it with the good size, stick it on your wheel and shoot. This is useful when you do 70 mm and you can’t open the red window (‘cause 35 mm are transparent, you know…)… And same thing for 220 film, note that after the twelfth shot, you just make a 360° rotation of the wheel…

### written by stouf

1. #### kylewis

That's fantastic! all beyond me, I think that's why I like random holgaramas... of course all that overlapping is planned!

almost 5 years ago ·
2. #### stouf

Oh thanks for publishing that LSI ! I wasn't expecting it... : ) ... And I'd be curious if someone could test it for the Diana...

almost 5 years ago ·
3. #### stouf

Oh and if you don't like its design (I'm not good at that stuff) just keep the triangles position and remake you version of it ! Lomo on !

almost 5 years ago ·
4. #### azurblue

Smart idea !

almost 5 years ago ·
5. #### kirri-joy

fan-bloody-tastic idea stouf. i always screw up 35mm in my holga, in the end i give up counting clicks. this is great!

almost 5 years ago ·
6. #### kirri-joy

this is also great for 3200 ilford b+w...its super hard to see the faint numbers in a dark pub at night.

almost 5 years ago ·
7. #### dogma

Cool I love math :)

almost 5 years ago ·
8. #### lomosexual_manboy

Stouf, you are a wizard. I'm going to use this for sure.

almost 5 years ago ·
9. #### ebolatheelectricmonk

Just what I needed! My rule of thumb (1+1/3 turn at the beginning, a little less than one turn at frame 12) works only partly.
That's much better!!

almost 5 years ago ·
10. #### friskas

over 3 years ago ·
11. #### itsdebraanne

i'm so confused

12. #### stouf

@itsdebraanne Mmm sorry to hear that... Here's an example: After you took shot N°1, turn the wheel a full 360° until reaching again mark N°1. Then turn the wheel until you reach mark N°2. You can now take shot N°2. : ) Is that clearer ? : )

13. #### itsdebraanne

@stouf i think? haha. do i turn the wheel a full 360 after shot No. 2, then turn to mark 3?

14. #### stouf

@itsdebraanne: Exactly ! : )

fantastic

16. #### djramsay

sorry would this work for the 120 wpc?