One answer to a burning question

Have you ever wondered, when stacking a teleconverter and an extension tube, whether it is better to put the TC behind the ET or the ET behind the TC? Neither have I, and yet I set out this morning to get the answer.

 

The photos below were both taken on a D810 with a 50mm f/1.2 Ai-s lens with a 14mm PK-12 extension tube and a Kenko TelePlus Pro 1.4x teleconverter. For the first photo, the equipment was arranged as Camera -> TC -> ET -> Lens; for the second, Camera ->ET -> TC -> Lens. The set aperture was f/5.6 (I have no idea what the effective aperture was.) All sharpening and corrections were disabled.

 

 

As you can see, there is very little difference between the two images. Either image is very slightly sharper depending on where you look.

 

I did notice that the second arrangement (Camera ->ET -> TC -> Lens) did not allow me to get quite as close (physically) as the first one. However, final magnification is the same, so that's only a difference in working distance.

 

So, there's an answer! For this particular combination of gear, it makes virtually no difference how you arrange the pieces.

 

You're welcome! :P

Interesting field test.

 

The physical arrangement matters when the the Tele-converter being used will not mount to the Lens because of the length of the rear section of the Lens: in this situation the Extension Tube serves a dual purpose - it also allows a physical space into which the rear of the Lens will sit.

 

For example, in Canon DSLR gear, the (Canon) Tele-conveters will not (physically) mount to several Lenses because of the reason stated above: (typically) all which is required is a 12mm Extension Tube, placed between the Lens and the Tele-converter, to allow the combination Lens>Extension Tube>Tele-converter>Camera.

 

This might be the case with (some) Nikon gear, I am not sure.

 

Also (with Canon gear) employing a third party Tele-extender, may negate this issue: for one example the EF 85/1.8 will not mount to a Canon Tele-extender because of the Lens's rear section, however that Lens will mount to (some models) of Kenko Tele-extenders.

 

WW

I have the 3 models of the Kenko tele-extenders - purchased as they were much cheaper than Nikons - and found soon after, that I could attach any of my 10 Nikons lenses at the at time. win win situation.

I have the 3 models of the Kenko tele-extenders - purchased as they were much cheaper than Nikons - and found soon after, that I could attach any of my 10 Nikons lenses at the at time. win win situation.

 

I have the Kenko 25mm tube. It's great to have a tube that provides pass-through communication and even screw-drive AF between lens and camera. I'm too much of a cheap bastard to buy the full set, though.

i'd say "try it"but not on a totally "flat"subject, that is pretty useless in my view.

See what it does to matter in front and behind the focal plane.

 

Differences would become vissible in the corners and at the edges of the resulting picture.

 

Also try a grey or white card so you can see the the "falloff" .

Try a shot with like a wineglass backlighted, to show internal reflections between the TC and main lens.

 

I would expect better results from the Tube first and then the TC, because tubes always have some "Internal reflection"which can cause a haze in the center of the picture, which would be enhanceed by the TC if it is at tha camera side of the contraption..

Edited June 14, 2020 by c.p.m._van_het_kaar

how close can you get just using the extension tube, or a longer one, I don´t see the advantage in using a TC in this setup.

There must be a reason why some TCs have a protruding 'nose' that gets their front glass closer to the rear of the matching lens. And whatever optical advantage that might give will obviously be destroyed by sticking an extension tube in there.

 

But if the TC is just a generic 3rd party offering, then all bets are off.

 

"A burning question"?

Not something that ever kept me awake at night! But then I'd only use a TC as a last resort anyway.

Edited June 14, 2020 by rodeo_joe|1

"A burning question"?

Not something that ever kept me awake at night!

 

I should know better than to try irony on the internet.

how close can you get just using the extension tube, or a longer one, I don´t see the advantage in using a TC in this setup.

 

Well that's another question—and one that people may actually ask. It's a given that adding a TC into the mix will result in higher magnification than using an extension tube alone. But which yields better results: an extension tube of length l in combination with a TC, or an extension tube of length l + a by itself, assuming both setups yield the same magnification? I think this question has been investigated, although I haven't searched for any findings in the internet.

The best description of this topic I have ever read is in John Shaw's book, "Close Ups in Nature", page 110. Here is a quote "Only at infinity focus is multiplying the focal length the same as multiplying the magnification."

I recently acquired a Vivitar 100mm macro lens with its 1:1 adaptor, AND two sets of three extension tubes, AND a 2x teleconverter, all bayoneted together, it was over a foot long. The seller said he used it to photograph a fly, focus stacking with a massive number of images. I can't remember what order they were assembled in.

As long as there is mechanical compatibility, if the TC is next to the camera, the extension tube adds to the focusing of the lens at its native focal length. For the same absolute magnification, the working distance will be less than if the TC is mounted to the lens. In the latter case, the extension tube augments the focusing relative to the magnified focal length.

 

John Shaw, nature photographer, prefers one over the other. That I can't remember which speaks volumes. Like a previous responder, I use a TC only reluctantly, and never for closeups. I do prefer using longer lenses for closeups in nature, for the added working distance.

 

Ed Ingold

Camera-TC-ET-Lens - TC multiplies the magnification

In this setup, the extension tube (ET) increases the magnification of the lens, and the TC then multiplies the resulting magnification.

 

Camera-ET-TC-Lens - TC multiplies the focal length

In this setup, the TC multiplies the focal length of the lens. The extension tube then increases the magnification of the resulting lens/TC.

 

The magnification of a lens and extension tube is given by: extension / focal length.

It should be plain that a given extension tube will increase the magnification less when attached to a longer lens. Therefore the first combination above will result in higher magnifications since the ET is applied to the native lens, not the longer lens/TC.

 

Which of the two combinations will give better results will depend on the individual lens, TC and the amount of extension. Some combinations will work better in the first setup, others will work better the other way around, and for others it won't make much difference. I don't think it is possible to make any generalised rules about which is better, you need to try and see what works.

I do prefer using longer lenses for closeups in nature, for the added working distance.

yup, me too.

 

I've been using the 200-500mm recently for butterflies. ~420mm and just under 2.20m doesn't scare them too much. Mine's a bit soft at 500mm.

 

Works well with the TC14 II at close range. Haven't tried an ext. ring. It might snap!

 

Did Nikon never make any 'custom' tubes for longer teles?

 

EDIT. Just found the TC800 1.25 for AFS. Does it only work on the 800mm E? Seems a shame!

Nikon made the TC 301 teleconverter, a 2x tc made for Nikon AF/AIS lenses 300mm or more. If attached to a AF lens, focus was done manually.

The TC800 1.25 is made specifically for the AFS 800/5.6, but but I am fairly sure it would fit other super-telephotos. As far as I know there is nothing to physically stop it fitting. Adding it to a 400/2.8 would give a nice 500/3.5, and a 600/4 would become a 750/5. Although not optimised for other lenses, I guess that performance should be good as TCs designed for telephotos tend to work well across all telephotos, and low-power TCs tend to have less impact on image quality than stronger ones.

 

Nikon never made AF extension tubes but there are third party options. Nikon's extension tubes (PK-11, PK-12, PK-13, PN-11) are from the 1970s and 80s, they are very well made but only support AI metering - no CPU contacts.

As far as I know there is nothing to physically stop it fitting

However, there's nothing physically to stop you using a 200-500mm on the nifty J5.... so Nikon did it in software...:(

 

Ah, the 400mm 2.8, the basis of many wonderful combos....:cool:

Did Nikon never make any 'custom' tubes for longer teles?

 

How long would you expec such a "Custom"tube" to be, to show any effect on a "long tele"?

How long would you expec such a "Custom"tube" to be, to show any effect on a "long tele"?

I'm glad you asked because I was about to ask...!

 

AFAIK, the old idea of adding the same as the focal length, ie 50mm extension for a normal 50mm lens got you to 1:1, so I guess you'd need 135mm to get the Sigma 135mm to a 1:1 macro (inf. not available!)

 

So 300mm for a 300mm 2.8....?

 

Humm, maybe not a good idea then!

I'm glad you asked because I was about to ask...!

So 300mm for a 300mm 2.8....?

Humm, maybe not a good idea then!

Xactly... :D

The formula for a thin lens can be used as an approximation.

 

1/d + 1/d' = 1/f

 

f = focal length; d = lens center to the subject and d' = lens center to the film plane. The magnification is d'/d. d = d' = 2f at 1:1 magnification.

 

While 1:1 is the holy grail number for internet experts, a majority of closeups in nature are far less demanding. I managed to use a Hasselblad with a set of tubes, 16, 32 and 56 mm, with a 180 mm lens for flowers, leaves and fungus at a comfortably long working distance (> 12").

 

Don't forget you can extend the lens considerably with the focusing helix alone, and that adds to the tube length.

Using a little algebra, we can estimate the amount of extension to achieve a certain magnification ratio

 

L = FL x magnification, where L = the total extension including that of the focusing helix.

 

To get 1:4 magnification, a 4x6" field of view, with a 300 mm lens, we need 75 mm of extension. This would probably require a 50 mm extension tube, but would give a working distance of 4(300 + 75) = 1500 mm, which rounds to nearly 60".

 

In real life, compound lenses behave differently, and lenses with internal focusing do so by shortening the focal length. As a result you tend to need less extension, and get less working distance for a given magnification. Regardless, you are unlikely to frighten skittish flowers or mushrooms with your attention.

 

You can use extension tubes with zoom lenses too, but focusing will no longer track the zoom level. That's not a deal-breaker if you take that into account. There is little aberration or field curvature at modest magnifications, and the quality is vastly superior to that using a closeup filter (diopter).

"and the quality is vastly superior to that using a closeup filter (diopter)"

 

Putting an extension tube between the lens and camera, moves the lens outside its design envelope and almost certainly will compromise optical quality. Don't believe that just because the tube contains no class that it won't have a negative impact. There are some lenses designed to work with extension, such as the old manual focus micros, but modern lenses with floating elements and internal or rear focusing are carefully optimised for use when attached directly to the camera and many do not perform well with extension.

 

On the other hand, a good quality two-element achromat diopter can give excellent results. They also have the advantage that when attached to zooms, the focus point remains steady when zooming.

Closeup filters work by shortening the effective focal length of the lens, allowing you to get closer the subject. If the lens is nominally focused at infinity, the working distance with a +2 diopter filter is 1/2 meters (~20"). The magnification is equal. to the FL in meters times the diopter strength. A +1 diopter on a 300 mm lens would give 1:3 magnification at 300 mm working distance (12"). Results with an achromatic filter would probably be pretty good at +1 diopter, but degrade significantly at higher power.

 

The downside is the expense and availability of achromatic closeup lenses. A 77 mm filter (Nikon 300/4) would cost about $500, if you could find one, and each lens needs a filter size to fit. Extension tubes fit all lenses with the same mount, and a set usually costs about $125. There is little or no degradation of the optical quality at modest magnification (e.g., 1:4). A dedicated macro lens will have a flatter field and less CA down to 1:1, perhaps greater if the lens is inverted.

Another downside of using closeup "filters"/ diopters is that they move the lens "outside its design envelope". ;-)