Almost finished my first pinhole camera

[Ric Johnson]

Don't forget to look at the f295 website. More pinhole information when you think exists.

[Existing Light]

I just developed my first pinhole print. Results were less than amazing It's waaaay underesposed. It's my first try, though, so I'm not too disapointed.

The picture was of a couch in the living room. I figured out the exposure for f/16 and then used a little math to figure out that my exposure time of about 70 minutes. There's a bit of an image, but not much.

I have the second one going now. I'm exposing my next sheet outside where it's a bit brighter. I determined that my exposure should be a little over 4 minutes, but I set my timer to 15 since my last sheet was so underexposed. Hopefully this one will turn out better

If anyone wants to know, I'm shooting HP5+ rated at EI 200. I'm developing it in Rodinal 1:50 at 20C. My aperture is 381, but I rounded up to the next fullest aperture. I dont have my notecard with me, so I dont know what that next full aperture is. (My notecard is taped to my camera).

I'll post scans when my film dries

[Existing Light]

Don't forget to look at the f295 website. More pinhole information when you think exists.

thanks for the link. I have it bookmarked

[RalphLambrecht]

I just developed my first pinhole print. Results were less than amazing It's waaaay underesposed. It's my first try, though, so I'm not too disapointed.

The picture was of a couch in the living room. I figured out the exposure for f/16 and then used a little math to figure out that my exposure time of about 70 minutes. There's a bit of an image, but not much...

Share your math with us.

Also, don't forget to adjust for reciprocity failure.

[Existing Light]

Share your math with us.

Also, don't forget to adjust for reciprocity failure.

Uh oh. If you're asking for me to share my math, there must be something wrong with my multiplication (which is very likely).

I finished my exposure and brought my camera and notecard in. I have an aperture scale in one of my photo books that only goes to f/64. I extended that out to f/512, which is the first full stop past my aperture of f/381


I figured out the aperture of my camera by dividing the pinhole diameter by the focal length. My focal length is 7.5 inches, which multiplied by 2.54 to get 19.05 cm. i multiplied that by 10 to get 190.5mm. I divided that by 0.5, which is my pinhole diameter. That gave me an aperture of 381.

I rounded up to f/512 because I knew underexposure was a problem. I didnt adjust for reciprocity the first time because I was like "well, let's see what happens before I start adjusting times." The negative turned out to be more underexposed than I anticipated

My second negative is ready to be developed, so I'll see how that one looks before reporting back here

[Existing Light]

Oh, I forgot to add how I got my times. I found the exposure time for the couch picture by finding the exposure at F/16. The exposure was 4seconds @ F/16. I used my aperture chart and saw that f/512 was 10 stops under f/16, so I added 10 stops to 4 seconds. That's what gave me about 70 minutes. Actually, I came up with a little more than 68 minutes, but I rounded up

[RalphLambrecht]

Oh, I forgot to add how I got my times. I found the exposure time for the couch picture by finding the exposure at F/16. The exposure was 4seconds @ F/16. I used my aperture chart and saw that f/512 was 10 stops under f/16, so I added 10 stops to 4 seconds. That's what gave me about 70 minutes. Actually, I came up with a little more than 68 minutes, but I rounded up

Let's think about this!

I agree with your f/stop calculation, but I think f/360, which is 9 stops from f/16 is close enough. Now to the exposure time:

You said you measured 4s at f/16 (are you sure, it wasn't 1/4 s at f/16). Assuming it was 4 s and the 9 stops above, this calculates to:

1st stop > 8s at f/22
2nd stop > 16s at f/32
3rd stop > 32s at f/45
4th stop > 1m at f/64
5th stop > 2m at f/90
6th stop > 4m at f/128
7th stop > 8m at f/180
8th stop > 16m at f/256
9th stop > 32m at f/360

and this doesn't even include reciprocity, which would take it to:

> 2h at f/360 (I don't think so)

It must have been 1/4 s, wasn't it? In which case:

1st stop > 1/2s at f/22
2nd stop > 1s at f/32
3rd stop > 2s at f/45
4th stop > 4s at f/64
5th stop > 8s at f/90
6th stop > 16s at f/128
7th stop > 32s at f/180
8th stop > 1m at f/256
9th stop > 2m at f/360

and with reciprocity failure:

6-12 minutes, depending on the film.

[Romary]

(are you sure, it wasn't 1/4 s at f/16).

That looks effectively very longue. How was the light?

[Romary]

I just developed my first pinhole print. Results were less than amazing It's waaaay underesposed. It's my first try, though, so I'm not too disapointed.

Do not worry, usually the first try is a disaster. With the time you indicate, I am surprise you are underesposed.

[DLawson]

You said you measured 4s at f/16 (are you sure, it wasn't 1/4 s at f/16).

FWIW, I grabbed my Luna Pro and set it at 200. My well lit basement rec room couch read 2-3s at f/16. The much dimmer lit (it is night) living room couch gave 60s at f/16.