Longest working distance lens @ 1:1 range?

l2oBiN · Post by **l2oBiN** » Tue Jul 02, 2013 6:24 am

What is the longest high quality objective for photographing bugs/insects at 1:1. The combo I have been using is 1.4TC+Nikon 200mm macro. Any way of achieving longer working distance without increasing the TC mag??

ChrisR · Post by **ChrisR** » Tue Jul 02, 2013 8:20 am

Pass.
I bought a Sigma tele-apo-macro 400mm, but sent it back. It didn't go as far as 1:1 though that could have been made to happen with a weak dioptre or tube, but it wasn't really very good anyway.

Presumably one of the "Process" lenses designed for 1:1, of suitably long FL, could be arranged, but I think they're all pretty small apertures. They're designed for huge coverage so may not excel on a DX sensor.

Guido · Post by **Guido** » Tue Jul 02, 2013 10:17 am

Be careful with specifications as they always give the distance sensor to subject.

Th lenses with intern focussing don't get longer as they focus close.

ray_parkhurst · Post by **ray_parkhurst** » Tue Jul 02, 2013 2:30 pm

You're trying to achieve the opposite of what most folks desire, so wouldn't doing the opposite be appropriate? Maybe add a divergent telextender lens on the objective end, and then compensate with extensions on the camera end to get the correct magnification?

I don't have any telextenders laying around so I can't try the idea. I also am not sure what the inherent penalty to NA this would cause.

Also, correct me if I'm wrong, but I don't believe adding a teleconverter changes the focal length of the lens or the working distance. Doesn't it just divergently magnify the (focused) image presented to it and then present a (focused) magnified image to the sensor?

l2oBiN · Post by **l2oBiN** » Tue Jul 02, 2013 2:49 pm

ray_parkhurst wrote: Also, correct me if I'm wrong, but I don't believe adding a teleconverter changes the focal length of the lens or the working distance. Doesn't it just divergently magnify the (focused) image presented to it and then present a (focused) magnified image to the sensor?

It converts the 200mm into a 280, and by virtue of increased magnification provides a bigger working distance for the same on sensor dimensions as the non TC projected image.

ray_parkhurst · Post by **ray_parkhurst** » Tue Jul 02, 2013 3:01 pm

l2oBiN wrote:
ray_parkhurst wrote: Also, correct me if I'm wrong, but I don't believe adding a teleconverter changes the focal length of the lens or the working distance. Doesn't it just divergently magnify the (focused) image presented to it and then present a (focused) magnified image to the sensor?
It converts the 200mm into a 280, and by virtue of increased magnification provides a bigger working distance for the same on sensor dimensions as image not TC projected image.

OK, that makes sense.

I guess there is no free lunch...adding the telextender to the objective end lowers the NA the same as adding a teleconverter. No matter how you increase the effective focal length without proportionally increasing the exit pupil diameter you still proportionally reduce the aperture. Only answer is a big, expensive lens.

rjlittlefield · Post by **rjlittlefield** » Tue Jul 02, 2013 11:18 pm

l2oBiN wrote:
ray_parkhurst wrote: Also, correct me if I'm wrong, but I don't believe adding a teleconverter changes the focal length of the lens or the working distance. Doesn't it just divergently magnify the (focused) image presented to it and then present a (focused) magnified image to the sensor?
It converts the 200mm into a 280, and by virtue of increased magnification provides a bigger working distance for the same on sensor dimensions as image not TC projected image.

A quibble: both viewpoints are sort of correct but incomplete.

A 1.4X teleconverter does not convert a 200 mm lens into a 280. It simply increases the image size by 1.4X, as Ray says.

At infinity focus -- and only at infinity focus, this is indeed equivalent to converting a 200 mm lens into a 280.

But at closer focus distances, the combo's behavior does not correspond to any particular change in focal length.

Where the 200 by itself will focus from infinity to 1:1, the 200 + TC will focus from infinity to 1.4:1.

The working distance at which the 200+TC achieves 1:1 is equal to the distance where 200 alone achieves 1:1.4. This is farther than where a 200 alone would achieve 1:1, but it's not as far as what a real 280 would give.

Unfortunately, as far as I know the only answer to I2oBiN's original question is to use a longer lens, with all the issues noted by other posters.

--Rik

Guido · Post by **Guido** » Wed Jul 03, 2013 12:40 am

I use a Canon 500D close-up lens on my 300mm tele. That gives a long working distance but not 1:1

some examples

ChrisR · Post by **ChrisR** » Wed Jul 03, 2013 2:46 am

Me too, but , the greatest WD one gets with a 500mm ( 2 diopter) close-up lens is 500mm.

A "simple" lens focused at 1:1 gives a WD of 2x the Focal Length.
If you use a 300mm lens focused at 1:1, the WD would be 600mm.

I have visions of a 500mm (mirror?

) lens on 500mm of extension.

The working distance would be about 1 metre, it would be almost impossible to find the subject, working with 2mm dof, and the quality -??

ray_parkhurst · Post by **ray_parkhurst** » Wed Jul 03, 2013 10:24 pm

ChrisR wrote:Me too, but , the greatest WD one gets with a 500mm ( 2 diopter) close-up lens is 500mm.

A "simple" lens focused at 1:1 gives a WD of 2x the Focal Length.
If you use a 300mm lens focused at 1:1, the WD would be 600mm.

I have visions of a 500mm (mirror? ) lens on 500mm of extension.
The working distance would be about 1 metre, it would be almost impossible to find the subject, working with 2mm dof, and the quality -??

That's sort of what I was suggesting with the add-on telextender...but the mirror lenses have the same disadvantage in max aperture that a macro lens + telextender would have, unless someone knows of a 500mm f/2.8 or some such beast...

seta666 · Post by **seta666** » Thu Jul 04, 2013 3:19 am

Longest WD I can think of is a 500mm mirror lens with 1:2 macro plus a 2X teleconverter, quality would be other thing.

Best quality either a 180-200mm macro lens like you are using or a 120-150mm bellows lens (most modern macro lenses change focal length at 1:1, the canon 180mm becomes a 120mm aprox lens)

Regards

ChrisR · Post by **ChrisR** » Thu Jul 04, 2013 4:05 am

with 1:2 macro plus a 2X teleconverter

Not quite sure what you mean, but,

You remind me Javier, there are "1:1 macro converter" devices. They're a combined tele converter and macro focusing thing. Was that it? I have two in Nikon fit, one with Vivitar and one with Teleplus written on it. They're identical.
I bought them with the intention of removing all the glass, which leaves a nice helicoid "focus mount". (Once you've found how to get them apart

) .
One is still intact so I can try it with the longest I have, which is a 400mm.

On a mirror lens, (which I don't have) it would make a very short combination.

Who would like to predict the working distance on my 400??

A similar thing, an Olympus fit Panagor, doesn't increase its length, but moves the lens group internally.

seta666 · Post by **seta666** » Thu Jul 04, 2013 4:21 am

ChrisR wrote:
with 1:2 macro plus a 2X teleconverter
Not quite sure what you mean, but,

..................................

A similar thing, an Olympus fit Panagor, doesn't increase its length, but moves the lens group internally.

Some mirror lenses have macro capabilities, some lenses get to 1:4 macro and others to 1:2; add a 2X teleconverter and you get up to 1:1 macro with a very short combo; adding 300mm extension tube to a 300mm lens is a bit unconvinient, I would say

I had one of those panagor macro teleconverteres, it would zoom to 1:1 macro with a 50mm lens; longer focal length would give less magnification. It has a teleconverter on an helicoid so it also acts as a variable length extension tube. Quality was pretty bad

l2oBiN · Post by **l2oBiN** » Thu Jul 04, 2013 1:59 pm

seta666 wrote: ...most modern macro lenses change focal length at 1:1, the canon 180mm becomes a 120mm aprox lens...

So does this mean a 200mm macro lens focused at infinity on 200mm extension would provide more WD than when it's focused at 1:1?

I guess the extension combo would be inferior in quality?

Marko

ChrisR · Post by **ChrisR** » Thu Jul 04, 2013 2:43 pm

So does this mean a 200mm macro lens focused at infinity on 200mm extension would provide more WD than when it's focused at 1:1?

If the FL shortens as you focus close, yes. "Older" design macro lenses don't alter the FL (or very little), but some, especially newer lenses, do move the optics about to correct for shorter focus distance. I guess the shortening of FL makes that easier to design.

I have a 28-300 whose FL is 135mm iirc at closest focus at the long end.
It's sharper to use it at infinity with a close-up lens/dioptre, than closest focus OR on extensions.
That part may (hopefully) not be the same with a more tightly controlled macro lens though.