How to slow down a pinhold camera

I made a couple of pinhole cameras, either from scratch or by modifying an old not too functional camera.
The distance from the pinhole to the film is in the range of 10mm to about 60 mm and I am using Kodak 100 Tmax film and the pinholes are as calculated using the pinhole calculator (Mrpinhole.com) .

I've seen pinhole pictures where the motion was blended due to long exposures. For example flowing water or oceanside scenes where the motion of the waves results in a soft milky texture and the non moving objects are clear and distinct.

I suspect these were made using paper negatives and their longer exposure time associated with them.

Any suggestions as to how to lengthen my exposure times. Depending on the camera they are in the order of one second and the moving water doesn't blend nicely. I prefer simple solutions, if possible.

Thanks

Any way to mount a neutral density filter? That might be a relatively easy answer.

I'm actually a little surprised your exposures are that short. But I know on my first foray into pinhole shooting, I had obtained some 400 film and discovered that wanted to be down in the sub-2 second range which was too difficult to time with a manual flap, so I bought some 100 film. (I don't suppose there's any ISO 25 stuff left.)

Two of the last 3 Worldwide Pinhole Photography Days were cloudy, even rainy for me, so that helped draw out my exposures. With films having high reciprocity failure, things get longer fast too. I used Ilford Delta 100 last year, and in a wooded setting, some exposures ran out into the 40 to 60 second range. I admit a wild reciprocity curve does add complexity -- or at least reduces the intuitive determination of exposure.

I should add, my efforts were with a 4x5 using about 160 mm or so pinhole to film and a Bronica body cap adapter at about 90 mm -- maybe that shrinks the optimum pinhole size -- I was up around f250 or so.

My 2 cents,

DaveT

Shoot ortho film. If you really want to slow things down then pop on a blue filter. Yes, you can shoot to paper as well, then you're looking at ISO 3 or so (depends on whether you preflash it, I always do and it helps).

Another thing you could do is do chopped exposures, i.e., open a press shutter or withdraw your hand or hat when you have the particular motion that you want, but close it when the scene is static. So you multi-expose. That kind of strategy is good for when you're trying to get particular effects in your frame. I have an example here:

http://keithwilliamsphoto.net/Closer to Home/Give Thanks Like You Mean It.html

Though in this case I think I just hand shuttered it a few times. And that was with a pretty fast film, actually.

ND filters or perhaps a nice #25 Red.

You can make the pinhole smaller than what the calculator says too.

TMAX100 will tolerate some overexposure so you could pretend it was ISO50 for the purpose of computing exposure times.

Get slower film, there are ISO50 and ISO25 films (Efke for one) out there. Or ortho film.

Switch to a larger focal length (smaller effective f-stop).

Switch to photo paper, ISO3 to ISO10 depending on the paper and light conditions.

Switch to a wet-collodion process.

Lots of ways to get longer exposures but probably the easiest would be a #25 Red or some ND filters and rating your Tmax100 at 50.

The ND filter or a slower film would be by far the easiest.

Slower film, smaller pinhole, ND filter. If there is room, put the filter inside the camera on the back of the pinhole. This will help maintain good contrast, as only the light from the pinhole will strike the filter.

Efke 25, rated at 12 is getting pretty slow as far as conventional films go.

Smaller pinhole with an FL of 10mm is going to be difficult, you're already under .2mm at that distance. For the 60mm not to hard, but there may be issues with changing the pinhole size. Though last time I looked at the calc at Mr. Pinhole I think it uses the 1.9 constant, and many people recommend using a 1.5 constant which will yield a smaller pinhole, so there may indeed be room to play.