Entrance pupil position - for panoramas

[Malcolm_Stewart]

I've recently bought a Manfrotto 303Plus panorama head, and I've now spent a bit of time finding where the entrance pupil positions are for 3 of my fixed lenses.

One of my results was a bit of a surprise: The distances are from the lens/camera body flange, and the entrance pupil lies forward of the body inside the lens.

EF 50 f1.4 ~60mm from flange - about where the aperture is
EF 85 f1.8 ~70mm - similar to above

EF 200 f2.8L ~40mm - i.e. very close to the flange

The 85 and 50mm lenses have their entrance pupils more or less where I expected, but the EF 200 f2.8 telephoto kept fooling me. Only when I followed what I was seeing in the viewfinder, did the variation in position of my 2 alignment rods start decreasing, and I got the 40mm figure above. (I found it difficult to get a precise measurement even using slim rods, and there's around 5mm of error in the figures quoted.)

The detented rotation mount which is part of the 303Plus head is a real boon in this type of photography.

Here's an example:

Willen Lake, Hospice & Church using the EF 200 4560 x 1000 pixels

The image is about 1/3 of the original vertical height - i.e. ~2900 pixels resampled down to 1000. On the original it's just possible to make out the spokes on the bicycle wheels.

Now to find something more interesting but with lots of detail.

[Benchista]

That's exactly what I would expect, as the 200mm is a telephoto design, unlike the other two. Try it with a wideangle - chances are if it's a retrofocus design, it will be in front of the lens.