I have read posts that suggest that, when stopped down, a budget lens can almost equal a more expensive one. I have decided to put this to the test with my old, budget, film era, 75-300mm Canon lens.
For this test, the camera was mounted on a sturdy tripod, the mirror was locked up, and a 2 second self timer was used – all to minimise camera shake. In addition, the focusing point was ‘micro adjusted’ to its optimum (see this previous post). Here are some of the results:
This shows the corner at 75mm f4. Bear in mind that this is a full format lens, so with the cropped format sensor of my camera, this section is about half-way out to the edge (all lenses tend to be sharper at the centre compared to the edge). This is unacceptably soft. This next one is at F16:
A lot sharper, but not pin-sharp. This would probably withstand printing up to A4 size. Zooming in to 135mm and looking at the centre of the frame, at F8:
Moderately sharp, again this would probably print OK up to A4 size. But when stopped down to f32, although the depth of field has increased, sharpness has taken a hit:
OK for a postcard size perhaps… Going now to 300mm, this shows the corner at f5.6:
Quite blurred with purple fringing – not nice. Stopping down to F16 improves things a little:
But this is still rather soft with purple fringing. This might print OK at A4 but it is pushing it a bit.
So my conclusion? Much depends on the final use. With care, stopped down to about f11-16 and in the middle of the zoom range, with a bit of sharpening I might be able to get an acceptable A4 print. Otherwise I better start saving for an L series lens (all donations gratefully accepted!)