70-300L change of mind

drbird wrote:

I think you will have a hard time to find extreme focus breathing –in particular the decrease of focal length- in old non IF designs, but it is very common nowadays. Yes IF is not the only fact which is responsible but contributes a lot – for example just focus by extension (using extension tubes) like in the old days and the effect of focus breathing is nearly gone.

And it for sure isn’t a linear function – it is true that the focal length is measure at infinity but depending on the lens some keep it quite nice until you approach the close focusing distance others start to drop of like you describe it. I didn’t test the Nikon lens mentioned but had to do so with a couple of Canon and old Hasselblad and Zeiss. There is a huige difference between old and modern lenses.

totleytom wrote:

"extreme focus breathing at the long end and close focus – in fact it gives roughly the same magnification as the 4.0/70-200 at 1.2m means same focal length"

Can I just check that I understand what you mean by this? That when set to 300mm and focused on something very close, it seems to give the same image as a 70-200 at 200mm?

What about at longer focusing distances? Do you have any feel for what distance you need to be at before it starts acting like a 300mm lens?

I think it was around 280-285mm (or moreso similar to 70-200 f/4 IS + 1.4x TC) at 25'.

To get to the same 300mm as the tamron 70-300 vc or 300 2.8 IS it seems to take something maybe more like moon distance :).

drbird wrote:

I think you will have a hard time to find extreme focus breathing –in particular the decrease of focal length- in old non IF designs, but it is very common nowadays.

Even when a lens decreases focal length a little, FOV will get more narrow. With focal length remaining constant, FOV will get even more narrow. Only when focal length decreases a LOT, FOV will get wider.

There are non IF lenses that have floating elements, which will change focal length.

FOV and focal length are not linked 1:1.

Yes IF is not the only fact which is responsible but contributes a lot – for example just focus by extension (using extension tubes) like in the old days and the effect of focus breathing is nearly gone.

That is incorrect. With an extension tube you just shift the focus distance range, the new MFD will show a similar FOV change.

And it for sure isn’t a linear function – it is true that the focal length is measure at infinity but depending on the lens some keep it quite nice until you approach the close focusing distance others start to drop of like you describe it.

It is way more linear than you think. Just look through the view finder while going through the focus range, and you will see it is very gradual.

I didn’t test the Nikon lens mentioned but had to do so with a couple of Canon and old Hasselblad and Zeiss. There is a huige difference between old and modern lenses.

Not really, look at the 70-200mm f2.8 family from Canon to see its FOV narrows similarly.

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Geraldo Hofmann