I’m feeling really deficient in the focal length department. After my trip to the Baigup Wetlands I’ve realised that if I want a picture of a Crake I’m going to need a longer lens. At the moment I’m capped at 600mm on full frame, 800mm full frame equivalent on Micro Four Thirds, and 960mm full frame equivalent on APSC sized sensors. Unfortunately I’m handicapped by the fact that I don’t have a spare $35,000 AUD lying around or camera to put the lens on or I’d get the Canon RF 1200mm f/8L IS USM. More affordable at $4000 is the OM System M.Zuiko Digital ED 150-600mm f5.0-6.3, but even that is currently beyond my budget. 

 

 

 

So my solution was to use my Sigma 150-600mm lens with a Canon x2 teleconverter on my Canon 80d which would give me the full frame equivalent of 1920mm. That is serious reach in anybodies book, but will it work? The first thing to consider is whether the Canon teleconverter will actually fit on the Sigma lens. If you look at the photo you can see that the lenses of the teleconverter protrude beyond the lens mount and into the lens. Would there be enough room in the Sigma 150-600 to accommodate this. The answer was a resounding “YES!”. The next question was would it autofocus. The problem is that on DSLRs the autofocus mechanism  uses a sensor in the bottom of the mirror box that requires a sub mirror behind the main mirror to reflect some light onto it.  If light levels are too low then the system just doesn’t work and the camera can’t autofocus. So that means a lens with a minimum aperture of f8 won’t autofocus. Having said that if we use ‘live view’ the mirror is moved out of the way and on Canon cameras Canon uses ‘dual pixel autofocus’ where every pixel on the sensor can function as an AF point. So in theory it should autofocus. That is good because the minimum aperture of the Sigma 150-600mm at 600mm is f6.3, slap a 2x teleconverter on and that becomes f12.6. So I set up a target in the back garden to try it out. Lo and behold the camera failed to autofocus when using the viewfinder, so OK I knew that was going to happen, but using live view it did. 

The next thing to consider was image quality. When using a teleconverter image, and especially 2x teleconverters, image quality takes a serious hit – the image becomes notably softer. The answer to this is to stop down. After a bit of experimentation stopping down to f16 improved sharpness slightly, but it means using incredibly high ISOs which has impact upon the image quality. I figured that I’d run the images through Topaz DeNoise AI and hope that I’d get something decent.

 

 

Now I just needed to test this out on a live subject. Luckily our back garden is frequented by lots of birds, so I set the camera on a sturdy tripod and just waited. The results were that using live view and dual pixel autofocus the camera would definitely focus, it’s just it does it very, VERY slowly. I managed to get some photos, but the bird had to sit in one place for quite a while and this was with good light levels in the middle of the day. It wouldn’t be practical for a subject in the shade at dawn. I tried to manually focus but I couldn’t move the focus ring in small enough increments to achieve fine focus. The best results were achieved with birds that were about 5m away. I tried on Ring-necked Parrots that were further away and there was huge hit to image quality, the picture were just not critically sharp.

 

 

 

 

 

Ahh well back to the drawing board.