Reversing a telephoto/retrophoto lens - what effect on coverage?

Just thinking... it is common practice to use a retro or telephoto lens backwards for macro work...

I can't remember why

I presume because the lens can be positioned much closer to the object with the back focus being shorter than the focal length?

Well.... what about lens coverage? Will a telephoto lens, backwads, have a significantly bigger image circle than if it were the right way around?

I reckon I ought to be able to work this out for myself with a bit of common sense - but it is half past my bedtime and my brain has faded

Why do you think it is common practice to use retrofocus and telephoto lenses for macro work? I ask because commonly used macro lenses are neither retrofocus nor telephoto.

Why do you think it is common practice to reverse lenses for macro work? The rule is that lenses designed to be used at infinity should be reversed when working above 1:1 to preserve their corrections. There are exceptions, e.g., heliar type Enlarging Ektars, that do very well below and above 1:1 mounted normally.

Angle covered = angular field of view. The direction the lens is pointing shouldn't matter if it is not designed with mechanical vignetting on the film side. This is often the case for lenses made for 35 mm cameras, much less common with LF lenses.

It is best to post sober.

Dan Fromm said:

Why do you think it is common practice to use retrofocus and telephoto lenses for macro work? I ask because commonly used macro lenses are neither retrofocus nor telephoto.

Click to expand...

It was once possible to buy adapters that would screw into the filter ring of your retrofocus lens and allow it to be reversed when fitted to bellows or extension tubes. These days most people may use dedicated macro lenses... but when using a none-macro retrofocus lens for macro work a very popular suggestion was, at least at one time, to reverse it.

Why do you think it is common practice to reverse lenses for macro work?

Click to expand...

Just explained that.

Angle covered = angular field of view. The direction the lens is pointing shouldn't matter if it is not designed with mechanical vignetting on the film side. This is often the case for lenses made for 35 mm cameras, much less common with LF lenses.

Click to expand...

I was interested in coverage. I have a very large aerial photography telephoto lens which covers 9" by 9". It is designed (obviously) to be used at infinity. I was just wondering, if I used it for portraits, whether I could reverse it. This would be a similar situation to using a 35mm retrofocus lens, reversed, for macro work. I was asking, if used reversed, it might have significantly larger coverage - maybe it might cover a much bigger plate?

That was all...
Reading it back it doesn't seem a foolish or unreasonable question.

It is best to post sober.

Click to expand...

I said I was struggling to work it out for myself as I was tired. I was in transit travelling back from overseas and it was very late. I was sober, thank you.