Confused on Pinhole Exposure between these two web site for F # 280 pinhole ...

[peter k.]

Pinhole F=280

Pinhole Camera Exposure Guide

Chart exposure values for a specified fstop

www.mrpinhole.com

PinholeDesigner [pinhole.cz]

www.pinhole.cz

Calculated mrpinhole no reciprocity added, for a meter reading for 100 asa film @ f16 of 1/30 sec = 5 Mins 12 secs
pinholedesigner no reciprocity added for same reading for 100 asa film but for f22 1/15th sec = 11 sec

What the heck are we doing wrong... thanks for any help

 

[summicron1]

you don't say what kind of light. The longer the measure exposure with a light meter, the more reciprosity failure you have to include.

that said, pinhole exposures are amazingly fluid-- run a test with both in the same camera/situation, bet you anything both exposures end up looking similar. ASA 100 film in sunlight would typically be 2 to 4 seconds, but if you mess up it's no big deal.

 

[grain elevator]

11 s is correct, if that's what you want to know.

 

[peter k.]

... bet you anything both exposures end up looking similar.

Hmmm not with same sequence shot, but shot some with longer exposure and have also shot with the shorter exposure and they both look ok.
This pinhole thing is got a strange grip, more loose as a goose rather than trying to get a perfect exposure.

11 s is correct, if that's what you want to know.

With reciprocity added PinholeDesigner says 44 secs.

Think will try a shot at both 11 and 44 and take a look.

 

[MattKing]

As I read it, if the meter says f/16 at 1/30 second, Mr. Pinhole is calculating the exposure for f/280 to be ten seconds - the bottom row shown here:

I think you may be reading the wrong row.

 

[peter k.]

I think you may be reading the wrong row.

Oh yes.... definitely ...
That's funny.. checked several times and made the same mistake again.

So they match within one second... makes sense, knew we were messing up somehow.


Btw .. that is one heck of a shot of yours on the WPPD site http://pinholeday.org/gallery/2022/?id=834

 

[MattKing]

Thanks Peter - glad we could solve the mystery

 

[DWThomas]

Well at least there's an explanation! Mr Pinhole is nice because it runs on a browser script so it's more or less computer independent, but in the past I have been unable to ascertain what sorts of assumptions it uses in the calculations. I find that more than a bit frustrating.

Pinhole Designer seems much more transparent but it's a Windows executable app, and as far as I know it's had no updates for a decade, so built in film data is a bit behind. I can say I shot Fuji HR-T X-ray film at EI 50 and got exposures in the range of 10 to 15 seconds at f/300 that worked on a sunny, slightly hazy day.

I have some smartphone apps targeting pinhole too, but didn't even think to try them this year. They're now on a new iPhone 13 Pro and I can only test so many things at once!

 

[GRHazelton]

I should try a pinhole on my Pentax LX. It meters off the film during the exposure as long as the camera deems necessary, or until its battery runs down. I've only shot moonlit color pix for 15 or 20 minutes. The results are really strange looking, showing the motion of the moon during the exposure, but perfectly exposed.

 

[Donald Qualls]

@GRHazelton I did that with a Polaroid -- one of the cheap pack film ones, a Model 210; I added filtration to the metering window to compensate for a pinhole, dedicated to 3000 speed film only. Worked great. Fast enough in bright daylight to more or less hand hold, but good down to well lit interiors without flash (a couple minutes limit on that Polaroid's exposure circuit).