Canon 100mm Macro Lens

Canon and Tamron macro lenses

Canon and Tamron Macro lenses extended

In my last post, I said that appearances can be deceptive.

Perhaps that’s something of a mantra in photography.

In this case, I’m talking really about the length of the lens and the focussing systems. And you can now see that the Tamron lens when fully extended is really just as long as the Canon.

This shows one of the most important points about the Canon 100mm macro lens which is that the focussing is internal.

This is important for a number of reasons.

The most important reason is that the length of the lens does not change and the front of the lens does not revolve when you change focus and this gives a number of advantages which I touched on before for my own type in photography.

One of the most important advantages is that I can use a rubber lens hood, and then press my lens against, for example, the wires or glass of a cage and I can focus the lens knowing that it will not get longer or turn round and that there will be no damage to the lens or the cage.

When it comes to the question of the actual work of macro photography, if you look further at the Canon 100mm macro lens we get to the question that Tony asked about the two settings for focus limiters.

The principle is quite simple.

If the lens has to focus from zero to infinity, the focussing system will have to travel a very long way and take a long time even with Canon’s very quick, ultrasonic motor system.

And of course by this time, the object that you are trying to get into focus may have flown away or crawled out of the frame.

So the idea of the focus limitation is to get an approximate distance that you know that you’re going to be focussing on and to set the focus to that distance.

And then hopefully, the amount of travel that the focus system needs will be much smaller.

This is, of course, a sound idea and will certainly help.

But in practice, I believe as I said before that by far and the best way of dealing with this matter is to switch off the autofocus system altogether and use manual focussing .

The Canon 100mm macro lens, unlike a number of autofocus lenses has got a very large rubber ring for manual focussing and its clearly designed for manual focussing .

However, manual focussing can be best organised in one of two ways.

One is that you can maintain your position and turn the focus ring around.

This of course has some of the same problems as automatic focussing because it will take time.

The other way is simply to set the approximate focus depending on the image magnification you want and then to physically move yourself and the camera backwards and forwards until you get the correct focus.

What is the correct focus? and why are autofocus system likely to fail?

The reason is quite simple.

Most autofocus cameras now have a whole range of focus spots which you can see in the viewfinder.

My Canon cameras, have several focus spots which can be set in different ways. I normally switch off all of them apart from the central one.

It is also possible in some cameras to move the focus spots around but this does take time.

And the main problem with automatic focusing is quite clearly that the lens will only focus accurately if your focus spot is absolutely over the object that you want photograph.

Let’s take a practical example.

Close up of a Fringe Tulip

Here is a photograph of a fringed tulip, a beautiful flower, which I photographed in studio conditions using a flashlight with soft box.

The focussing problems are clear.

If you focus absolutely in the centre of the image what you’ll a sharp background which might be your intention.

Still I wanted to focus mainly on the stamen.

There are obvious problems.

The stamen is not in the centre and therefore a central focus point would miss it.

I could perhaps fool around trying to get the focus point to hover over the right place but in my opinion, it’s much much easier and much better to focus manually.

manual focusing does have one or two problems.

Many modern cameras including my Canons have a mirror based reflex viewing system, rather than the traditional and brighter glass prism.

This means that you do need quite good light to focus accurately and in this case it was provided by the modelling light of my flash.

In brief, in many practical macro photography situations autofocus, even with the help of autofocus limiters. is not the best choice.

So it’s best to use manual focusing.

It’s manual for macro.

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February 2021
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Stock photography by John Rocha at Alamy

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