Haze with Pinhole

[anupam]

Hi,

 

It's great to have this new forum. I am looking forward to learning

from the discussion here.

 

Ok - so here's my opening question for the forum. I am just starting

out in pinhole photography. I modified the shutter and removed the

lens on an old kodak brownie 2A camera to make a 6x9 pinhole. I am

using Arista.edu 100 film. But I seem to be gettin a lot of hazy

pictures. I don't mean not sharp but more like lacking in contrast. I

do fine with the same film on my TLR, so I know I am developing it

right. Any suggestions would be welcome.

 

My guess is omething with the way I made the pinhole. It's about

f/250 but I made it on a piece of large format film behind which I

had stuck black electrician's tape to make it totally opaque.

 

-A<div></div>

[anupam]

I wanted to add that the above image was made at a 30 sec exposure, after accounting for reciprocity at 1 stop below sunny 16.

 

-a

[rjacksonphoto]

I wonder if the lack of a sharp edge caused by the tape has resulted in a lot of stray light rays, kind of like flare, that are decreasing the contrast of your image. Combine this with the loss of sharpness inherent to the pinhole, and you get these soft images. What happens when you increase contrast in PS?

[phule]

An AutoContrast and AutoLevels (usually my first test with an image) really seems to improve things in PS. Not the answer to your question, but it does help the scanned image :)

[anupam]

I can mostly get usable images with photoshop. But right now I am trying to do better in the camera itself, since I am learning the ropes for pinhole. I will look into the black tape suggestion. Indeed, that might be the key. I am wondering what else would be a good material to make a pinhole in.

 

thanks,

Anupam

[rjacksonphoto]

I use aluminum pie tin and poke the hole with a sewing needle. I then sand the edges smooth with steel wool. Might try that.

[silent1]

The large format film is most likely your problem. Even though you've covered most of the film with black tape to opaque it, there's still going to be a region uncovered around the actual hole, right? The D-max of your film isn't high enough to be perfectly opaque, first, so you have a region significantly larger than your pinhole that's admitting light, and that light will be scattered off the developed silver (assuming you used exposed and developed film); that will make a haze over the whole image, like flare in an uncoated lens, which raises the D-min and reduces contrast (especially in the lower exposure areas, meaning it will dull the blacks in the print). Second, if you didn't just poke a hole in the film, the film base will also scatter and refract light coming through the pinhole -- again, mostly creating what amounts to flare.

 

Alternately, if you just poked the hole into the combined film/tape sheet, the edge of the hole is probably both rather ragged and significantly deformed; reflection inside the hole can cause flare and produce the kind of haze you see.

 

I'd suggest trying a new pinhole made from a heavy duty foil baking pan, pie tin, etc., or from the aluminum side (the cylindrical part) of a soda or beer can. The pinhole material really needs to be very, very opaque right up to the edge of the hole (I've heard or people making pinholes, slits, zone plates and sieves with imagesetter film, but that stuff is optimized for high D-max and high contrast).

 

With the focal length of a 2A Brownie, f/250 is probably a little bigger hole than optimum (f/280 to f/300 is likely closer to "best"), but that would only lose you sharpness, not create haze, and the loss is small when you're this close to optimum hole size.

[anupam]

Thanks for the detailed explanation. I'll try modyfying the hole.

 

-A

[glenn_thoreson]

I see a couple of potential problems here. One, the film and tape are shiny. Any reflecting light will lower the contrast. Perhaps drastically. Second, electrical tape is not truly opaque. I found that out the hard way when trying pinhole work with Polaroid 3000 speed film. I use the bottom of the little aluminum pan that those 69 cent pot pies come in for making pinholes.

[Sandeha Lynch]

I bought some copper sheet from a craft shop after trying out foil baking tins because I realised that with use and abuse there was no way the foil would survive any damage. You can also get a firmer, and more importantly, a rounder hole by using a stiffer material. Copper is not as tough as brass, but still, it is rugged enough.<p>

One neat thing, IMO, is to cut the sheet to 35mm film size and slide it into a plastic slide holder. That gives you a solid and interchangeable unit if you're making your own pinhole camera boxes from scratch, but also it allows you to test the pinhole size by putting your pinhole 'slide' into a slide projector (damn near give-away on eBay these days).

<p>

Knowing the exact size of the pinhole helps in selecting an appropriate pinhole for the focal length and with judging the exposure, but at the very least, you can quickly spot which holes are ragged (and bin those immediately) and go on to refine your drilling technique to get a variety of perfect circles.