Extension Tubes

[Ukwildlifeo]

Originally Posted by Geoff F

Let's see if I can put my thinking on this subject in another way.

Doing all the theoretical camera maths doesn't make any real difference to the average 'in the field' user. It doesn't even matter if a lens is strictly 1:1 or any other ratio.

The very simple starting situation is: You can't get a large enough photo of a small insect with your current lens. So what are the options.

If that insect flies away everytime you get closer than 12 ins, adding tubes will not help, apart from a very small increase in magnification. The only answer is to increase magnification, which means adding a converter (subject to using a suitable lens) or getting a bigger lens. And either option isn't cheap, unless you already have a converter.

Extension tubes can help if your lens has a minimum focusing distance which is further away than, say 12 ins, (the fly away distance) like some 'macro' zooms which have a minimum working distance of 18 ins or more. I have even managed macro shots with my 150-500 lens by adding a 25 mm tube.

Tubes can also work well in other situations, like photographing a dead insect or some other object, like a small flower, which won't fly away when closely approached.

If you can, by various means of deception, get closer than the average fly away distance, a tube will also be beneficial.

But if your current macro lens already focuses quite close, adding a tube will only help to get you exceptionally closer which besides frightening the subject may cause other problems by creating a shadow zone or creating flash problems (if using flash).

So yes, extension tubes can help in some situations but they might not be the best answer for everybody all of the time.

Like Mike, I use a 180 mm macro lens and still sometimes need to add a 1.4x converter. For instance, today I needed to know if a fly was Eristalis tenax or E. pertinax and due to a mixture of physical barriers and fly wariness I couldn't get closer than 3 ft. But adding a converter did the trick; tubes wouldn't have been any help.

Ah right, sorry I see what you mean.

I tried the 150-500 on my extension tubes today - didn't work of course as mine don't have the connections and there is no manual aperture ring on the lens I'll have invest in a set of tubes with the electronic connections.

[squishy]

Originally Posted by Geoff F

For instance, today I needed to know if a fly was Eristalis tenax or E. pertinax and due to a mixture of physical barriers and fly wariness I couldn't get closer than 3 ft. But adding a converter did the trick; tubes wouldn't have been any help.

That's odd, I usually find Eristalis species very easy to approach.
I got close enough to one today that I could see the brown eye stripes that mark it as tenax with the naked eye.

[Geoff F]

Yes, quite often I can identify a tenax just with my reading glasses; but I prefer a good photo for other species (it gives me a bit more 'thinking time').

However, today they were a bit skittish and were lurking at the back of a shrub with no alternative approach route.

With regard to the 150-500 lens. I haven't tried this but I would have thought that if you set the lens autofocus to manual, then turned off OS and selected full manual control on the camera, something should be possible.

It would mean a bit of trial and, probably, a lot of error to get the camera settings correct though. But it is possible that this still wouldn't work.

Has anybody else tried this approach?