Topic: holga large aperture modification

[LT]

I was doing the standard wide aperture mod on my new holga today - the one that widens the widest lens aperture (not the one where you make the swinging arm actually useful) which went a bit wrong.  In fact, the whole coin sized plastic lens insert came away leaving the lens aperture the same size as you can see the plastic cover on the front of the lens.  It looks about twice the size that it was so I expect this will over expose by an extra stop - handy to know for lower light. 

I was wondering if anyone else has done this and how it affects the images on their cameras?  obviously there'll be a more shallow DoF but how about edge blur and vignette?  any pointers would be gratefully received before I start wasting any film though it.

I've taken the retaining screw right out so I can unscrew the lens and swap between my usual aperture lens and the wider version ... I'll report back with reports.

L

[gary m]

Hey Leon, check this link out. It shows how to remove the lens aperture washer and glue it on the aperture arm. You can then switch back and forth    http://www.flickriver.com/photos/ornellas/sets/72157617456109361/   

[Pitxu]

I'll take this opportunity to remind you that the swinging arm on latest models does in fact work correctly. F16 and f8.

I have two recent models, a N and a GN. The N version I've just taken out that little ring which changes the f8 to, I guess f5.6.

I'll be putting a roll through it this week.

[moominsean]

i took out the little plastic ring on one lens and didn't notice a difference.

[LT]

Just to be clear, I'm not talking about the little plastic ring, I'm talking about the whole piece of plastic that the little ring is attached to - it's diameter is about half inch/ 1 cm ish. It's that whole thing that I have accidently taken off.

Sean - taking out the plastic ring makes all the difference in the dull British light so you can expose 400 speed film with sufficient shadow detail (for my tastes anyway).

Pixtu - yes, thanks for reminding me. I'm so used to the proper Old holgas that I forget they have been improved. I've never found a need for a smaller aperture though - I think it detracts from the whole box-camera style and feel to using a holga. That said ,this extra-wide aperture I've stumbled across will prove more useful than a smaller one to me - if it work ok that is

[Francois]

This thing about opening the lens to the maximum possible got me puzzled a bit, so I took out my Holga, micrometer and optics book (Popular optics from Edmund Scientific... great book by the way) and came out with the following:

f/stop= Focal Length/Diameter of aperture

A Holga has a 60mm lens (or at least it should be since it's written on the lens barrel).
The lens diameter is 19mm on the exterior of the body (which is your aperture)

This makes the full aperture an f/3.2 lens.

And a depth of field of:

3.25 ft - 3.12 ft to 3.38 ft
6.5 ft -  5.99 ft to 7.09 ft
20 ft -  15.83 ft to 27.14 ft
33 ft - 22.98 ft to 58.50 ft

Notice that infinity in lost with your mod... but you gain a much wider aperture...
Can't wait to see what the camera will produce

[Pitxu]

A Holga has a 60mm lens (or at least it should be since it's written on the lens barrel).
The lens diameter is 19mm on the exterior of the body (which is your aperture)

This makes the full aperture an f/3.2 lens.

I think you need to remeasure/rethink this.

The aperture is not the exterior of the lens, but the hole that the light passes through.

I can't see any way of getting greater than about 10mm, thus about f6.

[LT]

Pixtu - the first picture here is a photo of the lens as it should be after the small plastic ring has been removed, the second shows what happened to mine - it is more than 1 cm across to my eye, but in the spirit of the Holga, I'm not going to measure it.

 

[Sorry, image deleted during forum software upgrade. Please re-upload if so inclined.]

[astrobeck]

The little rectangle that lets the light through is smaller than this opening you are showing Leon.
I think you are going to max out at whatever "that" opening is.

I'm not measuring either...but

Leon has me all curious so I'm going to run a roll through and check this out though.

Leon shall we have a shoot-out?

Becky

[LT]

I did wonder about that Becky - you mean the shutter aperture - right?  I guess, in theory anyway, the light should converge and flip at that point , but hey, this is a bloody holga we're talking about, right

[astrobeck]

I did wonder about that Becky - you mean the shutter aperture - right?  I guess, in theory anyway, the light should converge and flip at that point , but hey, this is a bloody holga we're talking about, right

Yes, the shutter aperture.  The little rectangle in the center of this photo.
Anyway, I have mine configured now  like the one you have shown.  I used a hose washer as a spacer to keep the lens from falling backwards into the housing.



[Sorry, image deleted during forum software upgrade. Please re-upload if so inclined.]

[Pitxu]

OK Leon, I see what you did now.

I only took out the small piece, shown in red on your photo.

The second image shows what I see from inside the camera. My new aperture (f5.6?) fits just inside of the square shutter hole.

I just finished a roll this afternoon and will post results tomorrow.

[Sorry, image deleted during forum software upgrade. Please re-upload if so inclined.]

[Francois]

I just checked the shutter like said before...
The square shutter makes it a bit hard to measure... especially since it isn't perfectly square!

It's 5.5mm x 7mm on mine...

If we consider that it's the surface of the aperture that's important. Surface of the aperture is 38.5 sq.mm
Diameter=2x(sqrt(surface/pi))
So the shutter aperture has a diameter of 7mm

So no matter how much you try and open up the lens aperture, the maximum you should get is an f/8.6

I must admit I'm quite surprised... 

That means a nice big squarish bokeh in perspective...

[LT]

this is getting well technical for a toycamera .... 

[Pitxu]

this is getting well technical for a toycamera .... 

WHAT!  WHAT? How dare you sir!

Pistols at dawn.

[LT]

or Dianas at dawn?

[moominsean]

yeah i was wondering why you questioned the possible outcome and didn't just shoot a roll to see.

[LT]

with the price of film these days, Sean..  What -  are you made of money or something?

[Francois]

That's pretty much why I learned to over-calculate and over-engineer everything. It saves money in the long run...

[Nigel]

I'm interested to see what these turn out like, I've got two Holgas. I could have a low light (or lower light) Holga and a regular one. Instead of changing the aperture you just change cameras!

[astrobeck]

I'm interested to see what these turn out like, I've got two Holgas. I could have a low light (or lower light) Holga and a regular one. Instead of changing the aperture you just change cameras!

Only two?