Stacking lenses in reverse for macro work

Question:

To get some of the highest reproduction ratios with regular lenses, one of the best options seems to be to reverse a wide-angle lense in front of a prime telephoto lense. I read somewhere that this should produce repro ratios equal to the ratio of the two focal lenses, i.e. if I have a 180mm lense and a 24mm one in front of it, the ratio should be 180/24 = 7.5:1. First of all, is this true? I wish I understood the optics behind this, and why this works at all.. Second, what determines the distance at which this contraption will focus? Third, what else can be done with this setup - i.e. an extra close-up filter inbetween does nothing (or even makes the ratio worse!); would putting extra distance between the two lenses change the ratio; would that change the focusing distance and the depth of field, too? Any other useful thoughts on this subject?

Thanks in advance.

Greetings,

Yes you can stack lenses in the way you suggest. The result of using a reversed prime lens in front of another lens, however, is no different from using a close up lens except the quality can be better than a single element close up lens. When you "stack" lenses in this fashion the optical effect is that the focal length of the combination will be determined by adding the diopter measurements of the individual lenses (doesn't matter how many just add them arithmetically). By definition the diopter measure of a lens is the reciprocal of the focal length in meters. A lens with focal length of 0.5 meters will have a diopter measure of 2, etc. Using that idea I calculate the focal length of your combination of 180mm and 24mm as being about 22mm. That means that with each separate lens set at infinity focus, the combination will be focused ar 22mm from the rear nodal point of the foremost lens which whch will put this combination very close to your subject and you might have trouble with lighting, etc. Also, at such distances you will have almost no depth of field.

Hope this helps.
--
Richard S.

Dmitry P. said:

Question:

Click to expand...

Answer:

See here http://www.stevesforums.com/forums/view_topic.php?id=15584&forum_id=50 and here http://www.stevesforums.com/forums/view_topic.php?id=17816&forum_id=20 The key point is that you have to find a matching lens pair (i.e., on-camera and reversed). Not all lenses can be paired due to various optical design factors. Traditionally, Nikon's MF lenses with 52mm thread are better choices. For example, 200mm and 50mm produce 4X (4 times of life-size) and 200mm and 24mm produce 8.3X. The drawbacks of using reverse lenses are very obvious. FIRST, a poorly matched lens pair will produce vignetting or light fall-off. SECOND, depending on the lenses being used, contrast and edge sharpness may be lower. THIRD, light loss may be significant forcing you to use slower shutter speed (and mirror lock-up is usually needed). FOURTH, focusing is difficult (even with a AF system) as DoF is very shallow.

CK

So I have actually tried this set-up before, although I didn't get a chance to get macro-couplers yet, so the 24mm 2.8 lens (the kind you mentioned, with 52mm threads) is holding on to the 180mm prime with a rubber band

I've dealt with some of the mentioned problems already... I shoot with the aperture small as possible and most of the time use a ring flash because of that. But I'm still wondering about how to improve this set-up - i.e. what combination of apertures to use.. Most people suggest having the front lens wide-open, but I get some CA on the edges this way.. Stopping it down solves this, but produces some vignetting; however if I also stop down the telephoto lens further, this effect seems to diminish. So what's the best combination?

Websites mention that flat-field lenses are the best for this - which ones are and which ones aren't?
And what will happen if I put more distance between the two lens?

And to whom who has done this, what specific combination of lenses worked well for you? I love the 7.5:1 ratio, despite all the problems...

Dmitry

Dmitry P. said:

I've dealt with some of the mentioned problems already... I shoot
with the aperture small as possible and most of the time use a ring
flash because of that. But I'm still wondering about how to improve
this set-up - i.e. what combination of apertures to use.. Most
people suggest having the front lens wide-open, but I get some CA
on the edges this way.. Stopping it down solves this, but produces
some vignetting; however if I also stop down the telephoto lens
further, this effect seems to diminish. So what's the best
combination?

Click to expand...

Stop down the lens on the camera and use the reversed lens wide open. But, you must have a good reversed lens, a flat-field one preferred.

Dmitry P. said:

Websites mention that flat-field lenses are the best for this -
which ones are and which ones aren't?

Click to expand...

24mm F2.8, 28mm F2.8 and 35mm F2.8 all have Nikon CRC feature. The 50mm 1.8 is also good.

Dmitry P. said:

And what will happen if I put more distance between the two lens?

Click to expand...

You get more vignetting and/or light fall-off.

Dmitry P. said:

And to whom who has done this, what specific combination of lenses
worked well for you?

Click to expand...

Many old-timer nature and macro photographers did it frequently. MF 200mm (or MF micro 200mm) plus 50mm F1.8 (or 24mm F2.8) work the best for me.

CK

Also, it seems that no underlying features of the lenses matter, i.e. if it's a micro-nikkor or a regular lens (except stuff like sharpness, of course). Is that so?

Hi, Dmitry

I have little or no idea about optics, so I'm afraid I'm not going to be able to answer most of your questions.

However, I have some experience working with reversed lenses (I said some, not a lot). I can assure you it's not an easy technique, you will have almost zero DOF and manual focusing (forget AF, of course) may become painful, literally painful for your eyes (and the small, dim viewfinder of most D-SLR makes things even worse!). You will also need a lot of light to compensate the telephoto lens closed diaphragm and the loss of light because of the attached lens. I tend to use a couple of external flashes. Maybe the built-in flash and a remote SB-800 will be enough with the D70. Of course, also forget hand-held shooting.

These samples have been taken with a S2 and a Nikkor 200 mm f4 AIS lens plus the reversed Nikkor 50 1.8.





Hard to catch these tiny bugs, but very rewarding when you achieve it!
Best regards!

Felipe

Dmitry P. said:

Question:

To get some of the highest reproduction ratios with regular lenses,
one of the best options seems to be to reverse a wide-angle lense
in front of a prime telephoto lense. I read somewhere that this
should produce repro ratios equal to the ratio of the two focal
lenses, i.e. if I have a 180mm lense and a 24mm one in front of it,
the ratio should be 180/24 = 7.5:1. First of all, is this true? I
wish I understood the optics behind this, and why this works at
all.. Second, what determines the distance at which this
contraption will focus? Third, what else can be done with this
setup - i.e. an extra close-up filter inbetween does nothing (or
even makes the ratio worse!); would putting extra distance between
the two lenses change the ratio; would that change the focusing
distance and the depth of field, too? Any other useful thoughts on
this subject?

Thanks in advance.

Click to expand...

--
http://www.beatusille.net
'Who are you going to believe, me or your own eyes?'
Groucho Marx

(Gear list in profile)

Felipe Rodríguez said:

These samples have been taken with a S2 and a Nikkor 200 mm f4 AIS
lens plus the reversed Nikkor 50 1.8.

Click to expand...

How much working distance do you get with this set-up? And how do you get subjects like a fly pose for you
Thanks,
Dmitry

You have really shallow working distance. The ant was shot leaning the lens (the reversed 50 mm in this case) on the table where the bug was taking a walk... I had to be careful to avoid smash the little bug! So go figure! I guess the bug was not more than 2 inchs from the lens.

The fly was shot in a cold day, so it was moving slowly. It was doing a regular walk on a window frame, so I awaited it...

Dmitry P. said:

Dmitry P. said:

These samples have been taken with a S2 and a Nikkor 200 mm f4 AIS
lens plus the reversed Nikkor 50 1.8.

Click to expand...

How much working distance do you get with this set-up? And how do
you get subjects like a fly pose for you
Thanks,
Dmitry

Click to expand...

--
http://www.beatusille.net
'Who are you going to believe, me or your own eyes?'
Groucho Marx

(Gear list in profile)