100-300 vs. 50-200+1.4TC: surprised!

Woza wrote:

thanks for this thread Luis, I've been prompted to check the focus adjustment of my "new to me" 50-200 + EC-14 and found that the reason I was losing detail with this combination at distance (compared to the bare lens) was that it need +12 focus adjustment dialled in.

This is very interesting info.

Brian can you explain how you got to +12 your method

I have a long distance focus target I use for all my lens testing, a large electrical pylon at about 800m away across the river (+ a couple of nearer complex structures at about 400m and 50m)

Hand-held shooting, smallest single point centre focus, two shots per data point. staring at zero, I went up to + 20 and down to - 20 in 5 unit steps, repeating the exercise twice (same general lighting but with a 5 minute break between complete sets)

Each data set step was repeated at 50,75,100,150 and 200mm

I also shot a close target at about 3 m following the same protocol

Downloaded into LR5.4 and the images were examined at 100% making subjective comparisons between each duplicate at the same step setting and between each step (looking to check variability within a set and between sets) LF JPG files used for this stage of tests

From this it was clear that the best sharpness at all focal lengths was in the +10 to +15 range

I then repeated the exercise in 2 step jumps between +10 and +14 and subjectively determined that the best results were obtained in the +10 to + 12 range

Since posting my original findings I have done some real life testing of Sparrow Fledglings at approx 25ft and 40ft (different birds) and decided that + 10 seems to be the sweet spot (the light has gone so I was shooting at ISO1600, in raw)

All this was done using the Default setting so it was applied across the whole sensor

Hope this is clear and sufficient information for your needs?