Article

Pinhole Adaptor

Nikon D300 with Pinhole adapter with T2 mount

Introduction

Having created my own pinhole devices and decided to search out pinholes, I came across a pinhole adaptor, and decided to get one as it has some advantages in some uses, and is simpler to use than the more elaborate experimental devices I have been constructing.

This does not fit directly onto a camera, and is designed to be used with a T2 Mount, available at extra cost.

You also get a cover that is made of the material you construct fridge magnets out of, so is lightly magnetic, that is used to protect the pinhole. In practice this is okay, and easy to remove, but comes off very easy so it needs to be kept in a close fitting plastic bag to keep this in place in your camera bag or pocket.

It is supplied with an A4 piece of paper giving some suggestions as to use and a piece of card that can be cut up to make an exposure calculator.

above left T2 mount - bottom right pinhole adaptor

The adaptor has a 3mm pinhole that is central. There are no adjustments. The pinhole appears to be the same type as you can purchase separately from the Pinhole Factory, who also supplied this adaptor.

Its far easier to use than the type I have made, although not quite as flexible.  There is no reason why you cannot put this on tubes to change the focal length, but you cannot change the pinhole size or the position of the pinhole.

The cost of the adaptor was £30 and the T2 adaptor, I also got at the same time, cost £10, both post free. As pinholes are £12 each the cost of building a kit myself using 4 pinholes is a little higher, but of course I needed then other materials, equipment and time. The same supplier had another option that would give similar results, you can send them your camera body cap, they add a 0.3mm pinhole lens and return it together with an exposure calculator for £30. This will only work if the camera body cap is made of a material that will not let light in. The Body cap would then not be a complete seal against dust. Most people don't routinely use the body cap, usually leaving a lens on, but would need it if they had to send the camera away for repair, so this is perhaps more or an option if you have several cameras or an old body cap from a previous camera, that will fit.

The advantages of the adaptor over making your own are:-

• ease of use - easier to use

• known size and position of pinhole

• simpler to take with you

• less likely to be damaged

• when used in public its more like just changing a lens, so causes less attention

• you are more likely to use it

• it is compact, and does not weigh very much so could be carried in any camera bag or a pocket without causing problems.

I personally prefer the Pinhole kit Mk3, that also uses the same type of pinholes, for experimentation but until I can get a version of the Pinhole kit Mk3 constructed to fit an adaptor, I will use this adapter for more general use. To see it in use take a look at the images I took at Stanton Drew Stone Circle - Pinhole Gallery. If general artistic work was the criteria as opposed to experimentation then this adaptor would be the one of choice. So I expect this to be used far more than my other options. The cost of this adapter plus a T2 mount was exactly the same as buying the 4 pinholes used to construct the kit I made.

Adaptor description and mounting options

This is a piece of metal that is shaped so as to hold a pinhole that is part of it, as far back towards the camera as possible, and fits a T2 mount.

T2 Mounts are used by some lens manufacturers, more in the past than today,  so that they can have a single lens that will then go onto many makes of camera. Devices like slide copiers are often constructed so they fit a T2 mount. The T2 mount is in two parts, a piece that screws to the lens, or other device, and a piece that connects up with the camera, these two parts are held together by screws allowing the relative position of rotation to be adjusted.

Pinhole adapter in T2 mount, looking at the side that connects to the camera. You can see the other side in the images with it on a camera Shown larger than actual size.

In this case, as the rotational position is not important, we just screw it onto the T2 mount and mount it on the camera. The thread on a M42 adaptor, that is usually used to allow something like a Practika or Pentax lens with standard screw flitting to fit another camera, is similar, and this adaptor will fit into a M42 adaptor but then sticks out of the back. I decided not to risk using this as you may have a collision with the mirror when it flips or other internal parts, altogether there would appear to be plenty of room and some lenses do stick out the back, and some even have filter holders on the back. If I did use the M42 adaptor it would give a wider field of view. I could use the M42 Adaptor if I used a tube element. The M42 adaptor option is therefore a possibility, if you already have one, to save purchasing the T2 Mount.

Pinhole adapter in M42 adapter, looking at the side that connects to the camera. The black part is the pinhole adapter and the shinny part the M42 adapter. Notice that this sticks out further into the camera than in the photo above when a T2 mount is used. This would give a slightly wider angle of view, but there is a small risk of contact with the mirror mechanism on some models, so this would need further investigation, before being used. Shown larger than actual size.

Focal length and pinhole size

The position the pinhole is held with the T2 mount, gives a view that is the equivalent to a 50mm lens on my camera (35mm on a full frame camera). Using my method of card wraps, I cannot get back as far as this and with the smallest tube its around 60mm, I can use a M42 adaptor with a card wrap and get more like 54mm, but this is less ideal.

Used directly on the camera with the T2 mount you get about the same view as from a 50mm lens and have an aperture of f167.

Ease of Use

It is easier to use because its similar to a normal exchangeable lens and as the image is a known size and position you can use another lens to set up the shot and work out the exposure.  The image with the pinhole in place is too dark to see in most situations, but you can quickly set this up with minimal effort by using the following steps:-

1. With the camera on the tripod look thorough a lens set at 50mm, set up the shot, and note the exposure. 

2. Without moving the camera, switch to the pinhole adaptor, instead of the lens.

3. Using the exposure calculator, you can work out what exposure you need.

Taking the photo this way, and with a little practice, you can get this right first time most times.

Camera settings

• Camera set to manual exposure, the exposure time only.

• Under expose rather than over expose (using the time set, exposure variation settings have no effect in manual).

• ISO set to allow exposure time you prefer to use.

• White balance set for the light condition, i.e. sunny, cloudy, shade ... although on my camera auto white balance works quite well.

• All camera menus, processing options turned off, or could be set up so as to increase contrasts and sharpness.

• Use with minimal enlargement.

Exposure

The exposure calculator has one scale that rotates within a another, you have shutter speed on the outside and aperture inside. Line up the exposure that you would use with your lens, for example 1/250 at f32 with ISO   set to 400, and then look at what the corresponding exposure time is with F167, you have F128 and F180 on the scales, so take the lower of these (F128), as with digital it's always better to under rather than over expose. In the example above this then gives you 1/16. If the time does not suit you then change the ISO, if you double the ISO you halve the exposure time, and if you cut the IS0 in half you double the exposure time, so in the example instead of using 1/16 at ISO 400, we could use 1/8 (twice as long) at ISO 200, or 1/32 at ISO 800.

We have an EV Guide you can use this instead of the calculator, although it goes to f64, exposures only have to be halved to give F128, and you can then get exposures for just about any situation and ISO. As half the exposure is shown one line above, this is already available.  The EV table is a three fold sheet with a table on one side showing EV values for each ISO against different exposure combinations, while the second side lists a large number of situations and gives the EV value for this. As you can add or subtract stops by simply moving up or down the lines in the table it is useful when using filters, teleconverters and in all types of experimenting.

Telephoto options

Used with Kenko tube set, which has 3 tubes, 12mm, 20mm and 36mm you can get 7 additional focal lengths.

The table below shows the theoretical focal lengths with different tubes in use, the aperture with this combination and a typical exposure on a sunny day  at different ISO's.   Times are shown in decimals of seconds for ISO 200, and the practical exposure value that you could use with other ISO's set, assuming you are using a scale with just full stops on.  The EV table, explained above, shows the in between steps if you are using a 1/3 or 1/2 stop setting within your camera menus, but this is a good enough starting point.

If you are using a a  different size set of tubes, or some other arrangement then you can get the relevant figures for your setup to create your own table from the calculator at  www.mrpinhole.com/calcpinh.php

Nikon D300 with 2 smaller tubes and pinhole adapter, so the equivalent of a 82mm lens.
Aperture from the table above is f273.