PART 1 - FIRST IMPRESSIONS (August 2010)
As much as I would like a Prime lens for those close up, in your face razor sharp images, not being a car driver could prove a bit difficult in transporting one of them about on my motorbike or public transport due to their size and weight. Instead I’ve opted for the nearest equivalent in the shape of a Sony 500mm/F8 Reflex lens which is basically a small mirror telescope in a small, light compact design and gives a long telephoto performance of 750mm with the sensor crop. Fortunately it’s the only reflex lens in any make that has auto focus and with the image stabilisation system built into the Sony Alpha range of cameras, makes for what could be a good package. There is a down side though. The aperture, unlike a zoom lens, is fixed at F8 so exposure is controlled by the shutter speed and because of the arrangement of the mirrors, the Bokeh (out of focus background) can appear unusual and also as small doughnut shapes caused by the front lens element.
I’ve thought about getting this lens before, cheaper for me than a proper Prime, but it was always the Bokeh that had put me off from getting one. I had come across on the internet a translation from a Japanese web site that said that Sony had finished the production run for this lens so that made my mind up. Get it now before the price went up due to rarity or there was no stock left. I headed off down to Duxford to give it a try out on anything that might be flying. It was a bit of a steep learning curve and turned out you need a different mind set to use it. With the camera set on Shutter Priority, and the ISO on AUTO, I was using a slow shutter speed for a bit of prop blur but the images were coming out essentially white or over exposed. I also wanted to keep zooming in and out, which of course you can’t do. I was having a problem so I sat down on one of the benches outside the AirSpace hangar and had a bit of a think as I chewed on a few ‘Jammy Dodgers’.
I was using the shutter speed as if I was using a zoom lens. Because of the mirrors in the lens, a slow shutter speed was letting in more light, hence the over exposure of the images. I went back to the rule of having the shutter speed the same as the focal length of the lens.1/500th of a second and above worked a treat. Once I sussed out about the shutter speed, I was quite impressed with the images I was getting. I did try the camera on Aperture Priority, but shutter speeds and image quality were all over the place so I went back to Shutter Priority. More practice to come over the weekend of the 4th & 5th September 2010 with the Summer Air Show at Duxford and the Air Pageant at Old Warden.
I’ve been using the Sony 500mm/F8 Reflex Lens rather intensively for the last couple of weeks including the arrivals & practice display at Duxford for their Summer Show and the Shuttleworth Air Pageant. I wasn’t confident enough to use it at the actual Duxford show although I should have as it’s a lot lighter that the Sony 70-400mm G SSM lens that I did use on the Saturday. I tried different filter combination's, including leaving it out, along with different camera settings and shooting styles. The general conclusion I have come to is that despite what I had read about the lens on various forums and reviews, you definitely need the grey coloured 4x Neutral Density filter fitted for aviation photography or basically any photography where a lot of light is going to reach the sensor. Like pointing it towards the sky. The filter is positioned behind the mirrors and cuts down on the amount of light, but not the colours, from getting to the sensor and consequently reduces over exposure of the image. This was happening quite a lot with the clear filter. Down side is that it’s now a little bit dark when looking through the view finder. Plus side, I can get shutter speeds low enough for a bit of prop blur on take off and landings but it does work best at 1/500 and above.
ISO was generally set on AUTO and ranged from 200 (the Sony Alpha 450 default) for flying to 1600+ for landing shots with a bit of background included. With the sun shining I had it fixed at 400 as 200 produced a slightly darker image. Leaving the ISO on AUTO may be the way to go and let the camera work out and compensate for the filter and deal with any image noise created by high ISO numbers in post processing.
The auto focus is a bit like that on a Tamron lens. Point it at a target, press the shutter release button part way down, and it zooms in and zooms out and locks. Not particularly fast, unlike the 70-400mm G SSM, but once locked on a target it holds it very well and you can hear the auto focus motor clicking away as it maintains its lock and focus. The camera is set for ‘Continuous Auto Focus’.
Due to the fixed aperture of F8, the only Auto Focus option is ‘Spot’ and the subject matter really does need to be in the centre of the frame for a good result. I have a few images where they are slightly off centre and one part of the aircraft can be razor sharp and the other slightly soft, but they were mainly on shutter speeds of around 1/320. A higher shutter speed would probably have solved that problem but the keep rate is better than the delete rate and the overall general focus and sharpness is very good. The best metering mode is also probably 'Spot' with 'Centre Weighted' coming a close second and you can use the 'Exposure Comp' to lighten or darken the image but that does up the ISO number.
The lens hood is very small and it was suggested on the forums and web sites that it should be replaced with a longer one to help cut down excess light from getting to the mirror and sensor. It was also suggested that rather than forking out for a new lens hood one could be made from black craft card with elastic bands to hold it in place. So in the best traditions of Blue Peter I used the black plastic cover off an A4 clip file, which length wise wraps around the lens with a bit to spare and cut it width wise to the same as that of the lens. It’s held together with sticky backed Velcro so I can flat pack it in my camera bag. With a large lens such as this, hand holding can be a problem when taking photographs due to any movement being amplified by the lens. I use a shoulder brace and along with the Sony Alpha in built camera stabilisation feature, I have had no problems with wobbly vision photographs. So Far.
PART 2 - GETTING TO GRIPS WITH IT (September 2010)