When I turn my focus to the minimum closest distance with marking at 1:2 ratio, I have an extremely difficult time to obtain focus in 1:1, but when I turn slightly to 1:2.5 or 1:2.2 minimal focusing distance, I find focus feasible as compared to 1:1 with the extension tubes. The closer to 1:1, the harder it is to obtain focus, perhaps due to the razor thin DOF.
With two different shoot out, I have to say that the extension tubes are good to retain bokeh, flare control and CA control with the lens with no addition of optical elements. But I find 100mm is too difficult for me to do hand-holding without tripod whereas 50mm is a bit easier to obtain focus for me.
Impressions & Notes:
- It is much harder to do hand holding with extension tubes on 100mm as compared to 50mm
- The closer I am with 1:2 original marking on macro lens with extension tube on, I find it extremely difficult if NOT impossible to focus.
- 1:1 macro is difficult to do without tripod
- Extension Tubes continue to benefit with no optical elements, flare control as well as CA are well within the limits of the lens used
- My 100mm usually stay about a foot from closest distance and with the extension tubes, that advantage of having a good distance in shooting bugs is lost
- Bokeh seems unchanged with the use of extension tubes
- In practice, I don't seem to be able to shoot in 1:1 at the 1:2 marking on my 100mm macro lens. I end up shooting most of my test shots in 1:2.2 and 1:2.5 marking.