On a recent trip to the Kirstenbosch Botanical Gardens I decided to carry along both my camera bodies. I have been using my older 550D as secondary, mostly to capture landscape shots using my wide angle lens, while I use the 7D and the 300mmF4 to get birding photos. The visit to Kirstenbosch was in the hope of seeing a Cape Sugarbird and add a new species to my list. I decided however to switch the wide angle out for a 100mm macro to get a few close up of the flowers at the gardens.
As a little test I decided to set up the same shot for each of the camera and lens combinations. I selected the vibrant orange clivias in the deep shade at the Dell as test subjects and set it up the best I could given the different focal lengths, aperture and sensor capabilities.
The 550D with the 100mm F2.8 had the low light advantage in that I could push open the aperture all the way to F2.8 and get in much more light. However the downside of doing that was leaving the flowers at the front of the bunch a little bit out of focus due to the shallow depth of field. The background is also much lighter but suitably soft due to the very shallow depth of field. Lastly the minimum focusing distance being shorter allowed for a closer bunch of flowers to be used as the subject.
The 7D had the 300mmF4 on it but I was also using my 1.4x extender – I was therefore shooting using an effective 420mm F5.6 (disregarding the crop sensor crop factor). Two full F stops less meant having to compensate with a longer exposure (1/200s versus 1/320s on the 100mm macro). But as you can see that only helped to a certain extent. The suggested rule of thumb is using 1/focal length as minimum shutter speed, which with the 300mm would mean limiting the shutter to 1/300s. However this would have meant having to compensate by increasing the ISO. And because I wanted to compare both lenses I decided instead to go with a little longer exposure.
The greater depth of field allowed for almost all the flowers in the bunch to be in focus. The minimum focusing distance on the 300mm is 1.5m, which the extender does not affect. However this meant selecting a bunch of flowers further back than the 100mm. This of course can be advantages when the subject matter is actually further back with restricted access, like I found in the orchid house at the Durban botanical gardens. However, I could not reach the leaf in the shot that is clearly not adding anything to the picture and could have otherwise been shifted out of the way. Setting up the shot allowed me to chose a more uniform background that was darker and get the good natural lighting effect.
Editing both pictures post shooting allows them to be lightened and some colour saturation to be introduced as the RAW images tend to be more neutral.
The verdict? Both lenses have their advantages and disadvantages. But they can be worked around (and I am learning as well through this post even). The shallow depth of field shooting at F2.8 needs better focusing and selecting a subject that’s in the same plane. The longer lens and F5.6 gives better focus through the image and a nice blurred background but because the subject matter was further away left a leaf in the image as well as created a much darker image. Which would I choose? Probably the 300mm image but if I could get rid of the leaf. If I go back I will definitely try again!
As a special bonus of using lenses for what they not meant to be doing, see below the landscape photo I took using the 100mm macro hand held on the 550D. Again I broke the minimum shutter speed, shooting at 1/15s due to being in the deep shade of the Camphor trees.