Shooting Macro

I love shooting macro, though inspiration can be a little tough to find at times. I already have a 105 mm Micro Nikkor, but had been thinking about a longer focal length for some time. After some research, it seemed to me that, rather than buying the 200mm f4 Micro Nikkor which has a 20 year old design, I’d be better off going with the Sigma 180 mm F2.8 APO Macro ED DG OS. My thinking was thus. Firstly it is a faster lens, very sharp and has a good reputation. The 200 mm Nikkor, is also stunningly sharp, and built like a tank, but it is very much a one trick pony. The autofocus is very slow (though satisfactory for things a long way off apparently) and it has a maximum aperture of f4.

Making a Purchase, Checking It Out..

So, at the last but one photography show in Birmingham, I visited the Sigma stand and spoke to a representative. After looking at the lens, and hearing about it’s performance, a purchase was made from London Camera Exchange. It duly arrived, at our local store, about a week later. Had it not been a bank-holiday weekend it would have been even sooner. It’s been superb! Out of the box, the Sigma appeared well made and robust. I fitted a Wimberley Arca Swiss lens plate and set about shooting tethered using Helicon Focus. This revealed an unexpected, yet key, difference with the 105 mm Nikkor.

Bearing in mind that I had always considered the 105mm Nikkor to be an excellent lens, I was not prepared for the stunning absence of chromatic aberration. It’s not that the Nikkor is particularly bad, it’s just that the Sigma has no chromatic aberration. None at all. At least, I haven’t come across it yet. There must be some somewhere mustn’t there? But the visible difference was remarkable. With the same subject you could see the artifacting on the Nikkor but not on the Sigma. Amazing!

Choosing Between Macro Lenses

Choosing a lens for shooting macro requires a little thought. Firstly, what do you tend to shoot? If it’s wildlife, there is something to be said for a longer focal length to keep you more distant from your subject. This is not the only relevant factor however. Most of my outdoor shooting uses available light, sometimes with a reflector or torch to provide fill or dimension. The physical length of the macro lens I use makes little difference in this scenario, but if I’m to use flash then I need to consider two other issues.

Flash and Macro Lens Choice

Clearly, for macro shooting with flash, the length of the lens itself makes a big difference to the type of flash you might use on camera. Will the flash be a Speedlight on a flash bracket? If so, a 105mm or 150mm lens will be more useful as you can get the flash nearer to the subject. The flash bracket can reach over the lens (as opposed to be in the lens’ shadow). Here I’m using a Custom Brackets CB Folding-T folding flash rotating bracket to hold an SB900, with a Neewer SB1520 small softbox attached, to light a subject from above and to the side.

Were I to attempt this with the Sigma 180 mm F2.8 APO Macro ED DG OS I’d be out of luck. On a D500, with the APSC lens hood extension, it is approximately 330 mm in length compared to the 190 mm of the Nikkor (or aprox 115 mm without the lens hood).

Using a Nikon Speedlight Commander R1C1 Macro Flash

If you are going to use the Nikon Speedlight Commander R1C1 Macro flash, for instance, you also need to bear in mind that there is no adaptor ring available in the 86 mm filter size of the Sigma 180 mm. You have to use the SB200s off lens in this case. Personally, I felt this was an inconvenience rather than a deal breaker, because when I work with flash it is usually in the studio and I can easily use stands for the flash.

Multi-Purposing a Macro Lens

It occurred to me that I have used my 105 mm Nikkor as a portrait lens in the past, ideal on a full frame camera. Would a longer prime be useful for some of my larger birds in flight work, for instance Osprey at Rothiemurchus? With a working focal length of 27o mm on a crop sensor camera (my D500), it might be a useful alternative to using my D810 with my 300 mm f2.8 (which is a much larger lens). This could be ideal for the lower light situations pre-dawn when the D810’s ISO performance is less suitable.

Lower-weight, and shorter minimum focal distance, make it a good choice for ad-hoc wildlife appearances closer to the hide.

Depth of Field Calculations

Sigma do not supply depth of field tables for shooting macro with their lenses, so ascertaining depth of field for close up work is not straightforward.

Doing the Math..

Some research was required to find out how to do the DOF maths, but with an Excel Spreadsheet I was able to produce a depth of field table. This has helped me appreciate how some of my shots might work – pre shutter release.

I guess, ultimately, if you take enough shots, you learn from experience, but knowing whether to make a virtue out of a wide aperture shot’s limited depth of field can be a little thought provoking if not enough image is sharp. I never mind taking many different shots whilst I’m out in the field, on the basis that one of them might be spot on. When I can get them onto the computer, It’s easy to see how I did, but I’d really rather know how to take the image work with a single click.

Lateral vs Longitudinal Chromatic Aberration (CA)

Types of Chromatic Aberration

Chromatic aberration occurs because shorter wavelengths of light (blue) are refracted (bent) more than longer (green and red) wavelengths of light which are refracted less. There are two types of chromatic aberration. Lateral (or transverse) and Longitudinal (or Axial).

Lateral CA occurs when all the colours are focussed at the same plane, just not aligned. R, G and B light are focussed sharply, but side by side. In Longitudinal CA, the colours are not focussed at the same plane, they are superimposed with blue in front of green in front of red. To observe this, Lateral CA causes coloured fringes around objects of high contrast, whereas Longitudinal CA causes patches of colour (ie. the most in-focus colour predominates).

The 180 mm Sigma Macro lens is particularly good with Longitudinal CA, you do not see colours change as you move up to, and then through, the focal point for high contrast details. Longitudinal chromatic aberration is very noticeable in the Nikkor 105 mm in comparison.

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