Can anyone help me with "Pinhole assist" app?

[rpavich]

Hi,
I'm using pinhole assist IOS app for exposure times but I need an aperture of 1/250 and I can't get the app to let me choose it.
Can anyone help?
Also, while I'm at it...is there anyone who has a better idea of how to calculate exposures rather than this app? I'm just wondering

 

[BrianShaw]

I don't know anything about pinhole assis app, but might be interested in learning.

Here is the resource I've used for a exposure computation method:



The other method I've used is a BlackCat Expsure Guide:

http://www.blackcatphotoproducts.com/guide.html

 

[rpavich]

I don't know anything about pinhole assis app, but might be interested in learning.

Here is the resource I've used for a exposure computation method:



The other method I've used is a BlackCat Expsure Guide:

http://www.blackcatphotoproducts.com/guide.html

Thanks, I'll check that out.

 

[dasBlute]

That's Joe Van Cleve, one of my pinhole heros from the f/295 days, a master.

Figure out your f/stop. My pinhole aperture is 0.4mm, distance to film about 150mm.

f/stop is focal-length / aperture

150/0.4 = 375 => F/375, which is about 9 1/2 stops slower than f/16.

I meter just as I would for any scene, get the f/16 exposure recommendation,
and double that 9 1/2 times. Yup. Then calc the reciprocity for the film.
Full sun for me is about a minute. Shady creek beds, about an hour.

Point it that-a-way and have fun!

-Tim

 

[rpavich]

That's Joe Van Cleve, one of my pinhole hero's from the f/295 days, a master.

Figure out your f/stop. My pinhole aperture is 0.4mm, distance to film ~150mm.

f/stop is focal-length / aperture

150/0.5 ~ 375 => F/375, which is about 9 1/2 stops slower than f/16.

I meter just as I would for any scene, get the f/16 exposure recommendation,
and double that 9 1/2 times. Yup. Then calc the reciprocity for the film.
Full sun for me is about a minute. Shady creek beds, about an hour.

Point it that-a-way and have fun!

-Tim

Ok..
My pinhole is .4 (I think, I have to double check) and my distance to film is 113mm.
113/.44 = f256

The calc app just said a 20 second exposure for the bright conditions for today. I made my exposure at 25 seconds just to make sure. I'll develop tonight after work. Hopefully it worked.

 

[DWThomas]

I have Pinhole Assist but have barely used it. It allows selecting f/256 which is well more than close enough for pinhole work. In a quick look it appears to offer steps of 1/3 stop, that's as close as you'll get with a regular manual camera.

What I have done, from back before I had a smart phone, is export a spreadsheet from Pinhole Designer, or create an equivalent, and print it on a little card to stick in my pocket. PD offers a "multiplier" for use with a regular meter reading at f/22. With that you note the shutter speed for f/22 for the film ISO you're using, multiply that time by the multiplier, and cook it down to minutes and seconds, as the multiplier is typically 150 or larger. You can work that sort of thing out from scratch by increasing the f-number one stop and making the shutter speed twice as long, in enough iterations to get close to your pinhole f-stop. I have normally bashed this into a small table so I can take a reading @ f/22, find the corresponding shutter speed in my table and next to that will be the actual exposure time I need.

Where the stuff gets a bit exciting is when you factor in reciprocity failure. That can get pretty serious with some films, e.g., twice the exposure length no longer gives twice the negative density. The aforementioned Pinhole Designer has the ability to include reciprocity compensation for some films. Unfortunately the program is old, ca. 2002 or so, and doesn't have some of today's films. There are also some questions about the reciprocity data for some films anyway, so in essence, there's no substitute for experimenting with the specific material you are using.

Here is a screen snapshot of one of the spreadsheets I describe. You will note the bottom of it is shaded to indicate to me "Don't go there!" I have sometimes joked that among the gear required for pinhole work is a folding chair.

As I mentioned. there is some question about the reciprocity data! For medium format pinhole, Fuji Acros has relatively low reciprocity failure out to a minute or two which is handy. Most of my recent shooting has been on 8x10 X-ray film, so all bets are off.

Edit: And several replies have happened in the time it took me to fumble this post together, so excuse any redundancy!

 

[rpavich]

I have Pinhole Assist but have barely used it. It allows selecting f/256 which is well more than close enough for pinhole work. In a quick look it appears to offer steps of 1/3 stop, that's as close as you'll get with a regular manual camera.

What I have done, from back before I had a smart phone, is export a spreadsheet from Pinhole Designer, or create an equivalent, and print it on a little card to stick in my pocket. PD offers a "multiplier" for use with a regular meter reading at f/22. With that you note the shutter speed for f/22 for the film ISO you're using, multiply that time by the multiplier, and cook it down to minutes and seconds, as the multiplier is typically 150 or larger. You can work that sort of thing out from scratch by increasing the f-number one stop and making the shutter speed twice as long, in enough iterations to get close to your pinhole f-stop. I have normally bashed this into a small table so I can take a reading @ f/22, find the corresponding shutter speed in my table and next to that will be the actual exposure time I need.

Where the stuff gets a bit exciting is when you factor in reciprocity failure. That can get pretty serious with some films, e.g., twice the exposure length no longer gives twice the negative density. The aforementioned Pinhole Designer has the ability to include reciprocity compensation for some films. Unfortunately the program is old, ca. 2002 or so, and doesn't have some of today's films. There are also some questions about the reciprocity data for some films anyway, so in essence, there's no substitute for experimenting with the specific material you are using.

Here is a screen snapshot of one of the spreadsheets I describe. You will note the bottom of it is shaded to indicate to me "Don't go there!" I have sometimes joked that among the gear required for pinhole work is a folding chair.
View attachment 191812
As I mentioned. there is some question about the reciprocity data! For medium format pinhole, Fuji Acros has relatively low reciprocity failure out to a minute or two which is handy. Most of my recent shooting has been on 8x10 X-ray film, so all bets are off.

Edit: And several replies have happened in the time it took me to fumble this post together, so excuse any redundancy!

Ahhh...thanks! That's helpful.

 

[DWThomas]

Ahhh...thanks! That's helpful.

Glad to hear that. As an old engineering type, I suppose I could get a lot more obsessive over "the numbers," but I tend to treat pinhole as more like cooking without a recipe. It sometimes amazes me how far off one can be yet still get something out the stuff. I've occasionally linked to this, but anyway, most of my lens-less photography in this millennium is out in my PBase galleries, including a bunch of stuff about the cameras I've constructed. (Well, I suppose it's a way to help stave off Alzheimer's ... ) That might provide some additional ideas of what can be done, ideas of what not to do, etc., etc.