An alternative to carrying extra lenses – a Macro Filter – James Allan

Helmet Orchid 2

2 Helmet Orchids growing in thick scrubland

A Digital SLR camera may be a little too bulky an item to lug around on bush walks.  I sometimes think that my former Panasonic Lumix was more versatile and lighter. Anyhow lugging the dSLR was what I had decided to do.  Then when I subsequently find a rare orchid that I have been wanting to photograph for a few years – I am left cursing that I didn’t carry my macro lens in the back pack.  There are however added problems in doing that; apart from the weight of the lens, changing lenses in the field is precarious and can leave dust motes on my sensor.  If I sacrificed my standard zoom lens and only carried the Macro Lens, I would be unable to take landscape or people photos.  

Trig Point

We Walked to Mount Magnificent near Nangkita

On this occasion I was rescued by the cannon 500D macro filter.  This is small in comparison to the macro lens and fits easily inside my camera bag.  It is easy to screw onto the front of the standard lens and allows me to get quite a bit closer to the tiny little orchids.  The images seem to be sharp without any major problems in quality.

When I first looked at Macro filters I was discouraged by an article that warned about severe drop in quality.  The early macro filters came in a stacks of three allowing you to additively increase the magnification.  Unfortunately they were subject to chromatic aberration.  This effect causes yellow and cyan fringing on the image, particularly near the corners of the frame.  It also causes a loss of sharpness.  It is because glass bends light of different frequencies by different amounts.

The standard lens on the SLR overcomes this problem by using compound lenses.  Two different glass elements, each bending the light in a different ways so that the chromatic aberration of the first piece of glass is corrected by the second piece of glass.  The Cannon filter is a little more expensive and has this 2 element design.  Thus there appears to be no noticeable aberration.


Fungi photographed on the same walk.

I was interested to discover that the filter made a significant improvement in Macro performance of my standard lens.  I was able to get perhaps 10cm closer to my subject and produce a much larger image of it.  However when I tried it with my Macro lens it made hardly any difference at all.  I also read that the degree of effect is greater with wide angle lenses and less with telephoto lenses.

An interesting and useful addition to your kit.  If you enjoy Macro work in the field, consider getting a Macro filter.

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