Canon 100mm + 1.4TC + 250D or 500D diopter?

I'm having one of those brain fade moments - when using the Canon 100mm macro lens with 1.4 Teleconverter do we normally use the Canon 250D or 500D diopter? I've got both but simply can't remember which one to use.

Well, that would depend on how tiny the subject is. On a (1.6x) crop sensor body, with the 100mm lens the 1.4 tc + 500D would give you a 4 x6 mm frame, at least according to my tests shooting mm lined subject . Very difficult to shoot underwater in reality.

I'm having one of those brain fade moments - when using the Canon 100mm macro lens with 1.4 Teleconverter do we normally use the Canon 250D or 500D diopter? I've got both but simply can't remember which one to use.

You don't need to use either one. The Canon 7D sensor for example is 22.3 x 14.9 mm. With the 100 and the 1.4 tele you get 16 mm x 11 mm or so. Adding diopters will make the field of view even smaller.

Bill

If I remember correctly, the 250D is a +4 diopter, and the 500D is a +2 diopter. I've used the 250D with excellent results. I'd start off trying it with the 500D.

shame they don't do them in 67mm thread size for the new 100mm lens..