Collecting • problems and possible rethink

I am encountering significant problems with my proposed ‘typology of bicycles’ concept for this assignment. My intention had been to use an OM-series 50mm prime lens on an E-30 (crop factor 2.0, therefore 100mm equivalent), wide open at f/1.4 to minimise the depth of field and suppress conflicting backgrounds.


However, I am finding the lens/camera combination difficult to use and I suspect that focussing is inaccurate. In the image above, I focused on the spokes of the nearest bike, but the sharpest detail is in the chainwheels of the furthest bike. With this focal length, my viewpoint is some 6m from the subject, which leads to practical difficulty in framing the shot in close spaces. This distance also means that the depth of field is correspondingly deeper. Even at f/1.4, nothing in the image above is sufficiently unsharp.

My next shorter focal length is on the kit zoom, 42mm (84mm equivalent) but the widest available aperture is f/5.6

With this combination, I am still some distance from the subject and far too much of the distracting background is sharp. At this stage, it is time for some calculations. I am using the Simple DoF application for iPhone.

With a Four-Thirds sensor and a 50mm lens, used at f/1.4 and focused at 6.0m, the depth of field (sharp zone) extends approximately 300mm to the front and rear and it has become clear that the ‘blur zone’ starts considerably further out. Stopping-down to f/2 to improve focusing accuracy extends the depth of field to 400mm in front and 460mm behind the point of focus, which is useless in the tight bike-park situations seen above.

Adopting the kit zoom at 42mm (84mm equivalent), f/5.6 and focussing at 4.5m gives a depth of field of 655mm in front and 970mm behind the point of focus.

It appears that my intentions are not achievable with the equipment currently available. At home, next week, I will make some test shots with an RB67. Calculated depth of field, assuming a 127mm f/3.5 lens focused at 4m, is approximately 200mm in front and behind the point of focus.

In the interim, I will make a start on ‘Plan B’, collecting bicycle details with a 42mm lens at f8 at approximately 600mm range. calculated depth of field is 22mm in front and 24mm behind the point of focus, so blur is eminently achievable.


Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Google+ photo

You are commenting using your Google+ account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s