Robber Fly

I do a lot of close-up photography with my Canon EF 300mm f/2.8L IS USM + 1.4x or 2.0x extender. That’s not the most usual combination for close-up photography, but has several advantages:

1. Long working distance: Due to the long focal length (420mm or 600mm) I can work at a longer distance from your subject than with a macro lens like my Canon EF 100mm F2.8L USM Macro. This is very useful when working with shy insects or when working from a trail and I don’t want to leave the trail when photographing subjects that are a short distance away from the trail (I might want to do this in order not to destroy any flowers that are between me and the subject or because in some national parks and other protected areas it may be forbidden to leave the trail).
2. It’s easier to get a calm background: Due to the narrower angle of view of the long focal length, it’s easier to isolate the subject against a calm background. Distracting subjects in the background (like other flowers, stems of plants or human made subjects) can often ruin an otherwise very good shot. I have written earlier for my reason to choose this combo as compared to a pure macro lens. A longer focal length is helpful when you want a clean and calm background.

Here I wanted to compare Canon EF 300mm f/2.8L IS USM and Canon EF 2X II Extender combo against Canon EF 300mm f/2.8L IS USM and 36mm Kenko extension tube. Basically I wanted to know which combination was sharper of the two. I used my Canon EOS 5D mark II for this comparison. All photos were taken using my Benro C45T Carbon Fiber Monopod as support. I fixed the settings as follows to get consistent result. ISO was fixed at ISO 800 & aperture at f/9.5. Shutter speed was 1/250 to 1/350 depending on the light condition as both combos differed optically. As a model I asked a Robber Fly to pose for me on the grass blade ;). As the Robber Fly just had lunch it was basking on that blade despite lot of insects flying around it. That gave me plenty of time to do my experiment.

First two photos here were taken using Canon EF 300mm f/2.8L IS USM and 36mm Kenko extension tube. This combination gives a fantastically sharp macro. Extension tube does not have any optical element in it. They also lack any electronic circuit in them, so you don’t see their mention in the EXIF information of the photo. By moving the lens father away from the sensor in the camera, the lens is forced to focus much closer than normal. The greater the length of the extension tube, the closer the lens can focus. Thus you can get a magnified view. This allows you to focus the lens closer than the minimal focal distance (MFD) of the lens. Not only do extension tubes reduce minimum focus distance, but maximum focus distance is also reduced. While not welcomed, this is part of the optical change made by the ET. For example, the Canon EF 300mm f/2.8 L IS Lens focuses from 4.5 feet to 10 feet with the Extension Tube. This is closer than 8.2 feet (2.5m) normally my 300mm allows without extension tube. Two drawbacks I find when I attach extension tube are my Infinite focus is lost and my magnification for distant object remains at 300mm focal length.

Second set of two photos here were taken using Canon EF 300mm f/2.8L IS USM and Canon EF 2X II Extender. This combination gives a relatively sharp photo. With Canon EF 2X II Extender Canon EF 300mm f/2.8 L IS Lens becomes a 600mm f/5.6 IS lens. Extenders do not affect the MFD (Minimum Focus Distance) of the lens they are mounted behind, thus the MM (Maximum Magnification) of the lens is also multiplied by 2x. I can stay away from the subject and get almost magnified view nearly double in size. With extender are my Infinite focus is intact and my magnification for distant object doubled to 600mm focal length. If you see the background bokeh it is more creamier with this combo. The optics in the extender cause deterioration of the image sharpness as compared to my earlier combo.

So which combination is better? Even though Canon EF 300mm f/2.8L IS USM and 36mm Kenko extension tube combo is sharper I prefer Canon EF 300mm f/2.8L IS USM with Extender combo for the advantage it has with larger focal length, larger working distance, and smoother bokeh. I also can shoot birds and other distance objects including infinity with higher magnification.

Insects in the Diptera family Asilidae are commonly called Robber flies. The family Asilidae contains about 7,100 described species worldwide. The Robber Flies are air hunters. They also known as an Assassin Fly and Bee Killer. All robber flies have 3 simple eyes (ocelli) in a characteristic depression between their two large compound eyes. The antennae are short, 3-segmented, sometimes with a bristle-like structure called an arista. Their eyes are set wide apart for good depth perception, with even a depression between the eyes to allow full sweeping vision. Also characteristic is the more or less hairy face (the “mystax“), which, it is theorized, protects the eyes during battles with large and dangerous prey. The high arching thorax containing the powerful muscles which activate the wings, allows it to fly up in an instant and snatch fast-flying prey out of the air. Robbers (unlike many similar appearing flies in other families) normally land with their wings folded together over the back of their extended abdomens, and this will help you pick them out. The long spiky muscular legs with which they capture and hold their prey (see especially the falcon-like talons at the ends of their legs).

The short, strong proboscis is used to stab and inject victims with saliva containing neurotoxic and proteolytic enzymes which paralyze and digest the insides; the fly then sucks the liquefied meal through the proboscis. Many species have long, tapering abdomens, sometimes with a sword-like ovipositor. Others are fat-bodied bumblebee mimics. Adult robber flies attack other flies, beetles, butterflies and moths, various bees, ants, dragon and damselflies, Ichneumon wasps, grasshoppers, and some spiders.

Robbers are in the Order Diptera, the true flies, characterized by having two wings (instead of the four wings typical of other orders). Two wings are much more efficient than four wings, and flies are the champion flyers of the insect world. Their hind wings have been reduced to little balancing organs (the halteres), which you can see on this fly as yellow knobs down below the wing bases.

Female robber flies deposit creamy colour eggs on plants or in gaps within soil, bark, or wood. Egg-laying habits are different depend on species and habitat. Most species lay eggs in masses and are covered with protective coating. Robber fly larvae live in the soil or in rotting wood. Larvae are also predators, they feed on eggs, larvae and other soft-bodied insects. They pupate in the soil and move to soil surface emerge as adults.