Wednesday, 30 June 2010

Home made stand off ring

A stand off extension ring is a ring for attachment to the filter threads of a lens, and allows for mounting something further away from the lens. It has the same diameter threads on the outside as on the inside.

This kind of ring has many uses. One can be to offset an attachment to the Panasonic Lumix 20mm f/1.7 pancake lens. Mounting a step up ring to the Lumix 20mm is not advisable, since it will cause the lens to jam when powering down. The front lens assembly is withdrawn into the chassis when powering down, which will cause anything wider than a normal filter to jam. But using a stand off ring between the lens and step up ring solves this problem.

Stand off rings are uncommon, and can even be pretty expensive. What's far more common and inexpensive, though, are UV protection filters. These can be bought from various auction sites at a small cost. You can remove the glass from these, and what remains is a stand off ring.

Here is an example UV protection filter:

Let's break the glass off it:

Be sure to use eye protection, and gloves. I used gloves then breaking the glass, but not in this illustration photo. Note that I put the ring into a plastic cup, to avoid having the shattered glass flying all over.

Breaking the glass takes a surprising amount of force. The round shape of the glass makes it extra strong. This is the reason why airplane windows are rounded: A rectangular shape is much weaker, especially in the corners. Hitting the glass towards one side may be an easier way to break it.

Once broken, remove the shattered remains:


It turns out that the glass was held in place with a threaded locking ring. Unscrewing this ring would have released the glass, without having to break it! Anyway, this was a cheap filter, so no harm done.

What I have now is a stand off ring, used to mount front lens accessories at an offset from the lens.

Here is an application of a stand off extension ring. A 52mm screw in hood is attached to the Lumix 20mm f/1.7 Pancake lens. As the lens has 46mm front filter threads, a step up ring is needed. However, connecting a step up ring directly to the lens is a bad idea due to the jamming risk discussed above. Using a stand off ring between them solves this problem.

Of course, attaching all this stuff to the moving front assembly of the lens is not a good idea. If you want a hood, it is better to use a light, low profile one.

Wednesday, 9 June 2010

Using older flash units

People who have previously used another camera system may have an old flash unit lying around. Chances are that you can still use them with your new Micro Four Thirds system.

Using a spare flash unit, rather than the built in on board flash, has many advantages. First of all, the dedicated flash unit usually has significantly more power, and can be used from a larger distance.

There is also the effect of having the flash further away from the lens, which means that you are less likely to get pictures with red eyes, and also makes the shadows somewhat nicer. Last, but not least, the external flash units can often be tilted, so that you can bounce the light off a white ceiling or wall. This will usually give much better lightning when taking pictures of people, as the light comes from a larger area, i.e., the ceiling or wall, and not from a single source.

Here are a couple of old flash units. Let's see how they can be used on the Panasonic Lumix GH1.

To the left is the Metz Mecablitz 36C-2, and to the right is the Nikon Speedlight SB-22s.

The Metz flash unit only has one connecting pin, and hence can only be triggered by the camera. No other communication is possible. The Nikon flash unit, on the other hand, has some more pins, and is capable of autofocus assist light and TTL. However, as this is a rather old flash, these functions can not be used on newer Nikon cameras, and certainly not on Micro Four Thirds cameras.

What can still be used, though, is the auto-function. The auto-function is a bit like TTL, except that the flash measures the light coming back from the subject, and cuts off the light when the exposure is sufficient. In TTL mode, the camera measures the amount of light coming back from the subject Through The Lens (TTL), and shuts off the flash at the correct exposure.

Since there is no communication between the flash and the camera, the flash does not know the ISO and aperture settings on the camera. So you need to give the flash directions manually. The picture shows the Metz flash rear panel, set in auto mode:
In this case, the ISO sensitivity is set to 100, the zoom is set to 85mm, which corresponds to 42mm on Micro Four Thirds. With this setting, the aperture can be set to f/8 (yellow), f/4 (green) or f/2 (red auto mode). Adjusting the ISO slider will give other aperture possibilities.

On the rear panel, you can also see that in this setting, with f/4, ISO 100 and 85mm zoom, the maximum range of the flash is approximately eight meters.

When using the flash in bounce mode, i.e., bouncing the light off a white surface, you generally want to have a wide angle flash zoom, and the effective range becomes smaller.

As for the Nikon flash, the rear panel settings are quite similar:
Again I have selected ISO 100, and with the selected auto mode, the usable aperture is f/2.8. The mode selector can be adjusted, to yield f/4, f/5.6 and f/8 as well, albeit with lower maximum distance as the aperture gets smaller.

Here is the Nikon flash in use, on Panasonic Lumix GH1:
The settings are: ISO 100, f/5.6, 1/160 second, manual exposure mode (M). The lens is the Panasonic Lumix G 45-200mm f/4-5.6 set at 45mm zoom.

I used this combination to take this picture, bouncing the flash off the white ceiling:
This picture showing the Pentax K10D camera with the Sigma 30mm f/1.4 lens, is not very interesting, but the exposure is good. Also, notice that the shadows are soft, due to bouncing the flash light off the white ceiling.

If you use this flash setup, and notice that the images consistently get too dark, then select a slightly larger aperture on the camera, as compared with what the flash rear panel says. And vice versa if the images consistently get too light.

Flash units can be used like this for virtually any camera, of course, as long as you can manually control the ISO, aperture and shutter. You will usually want to set the shutter fairly fast, e.g., 1/60 second, when using an external flash. This is to get a good balance of ambient and flash light in the picture. Normally, you will also need to set the white balance to "flash", to avoid the wrong colour balance.

Warning

Some older flash guns use a high voltage trigger, and could potentially damage the circuitry of the camera. Here is a list to check before using your old flash.