Macro lens + tc, greater working distance?

[mark_stephan2]

<p>Having just purchased the awesome AF 105 f/2.8 D micro I'd like to know what happens when using a tc. Does it increase working distance or magnification? Since this is a screw drive lens which tc would you recommend? Being budget conscious, would an old manual focus tc be just as effective as a newer af tc? If so, which one? About the af, it's not as slow as I thought it would be. The closer I get to the subject the more it hunts for focus but at greater distances af works great btw. Lastly, the lens is only f/2.8 when used as a telephoto and more like an f/5.6 lens when focuing up close. I assume this is the norm for a macro/micro lens.</p>

[ariel_s1]

<p>A teleconverter will give you more magnification. So the 105mm lens, focused at its closest to 1:1, with a TC14e will give you a 1.4:1 magnification. Working distance will be the same as without the teleconverter, as long as you are focused at the same place on the lens. So at closest focus without the teleconverter and at closest focus with the teleconverter, you will be the same distance from the subject. Therefore, given that you can reach 1:1 with a teleconverter without having to go to the closest focusing distance of the lens, depending on what you meant by your question, it could also increase the working distance of the lens.</p>

<p>As for which teleconverter you need, since you have an AF-S lens that doesn't have an aperture ring, I'd think that you need one that will communicate lens information back to the camera, so you'd want the newer teleconverters such as the TC-14E II. And about being f/5.6 up close, you are correct in that the effective aperture decreases. Do some google searching on macro lenses and effective aperture/effective f-stop and you will have all the information you could ever want about the mathematics behind the phenomenon.</p>

[Matthew Currie]

<p>A TC will increase magnification by the factor it's listed for, but the focus scale remains more or less accurate. A 2x converter will make your 105 lens a 210 at the same distances, so if you stand the same distance away your image is twice as big. If you want the same size image, you move approximately twice the distance away. Approximate, because there may be some inaccuracy, but it's close. </p>

<p>Autofocus cameras will hunt more with slower lenses so it seems reasonable that this would happen when you lower the F stop with close work. I doubt you will save anything in speed here since you lose two stops of speed with a 2x converter. </p>

<p>Still manual focus here, so can't address the equipment itself.</p>

[jim_momary]

<p>The 105mm AF-D became an AF-S in 2006, if I recall.<br>

Mark:<br>

So do you have an AF-D model as you stated or an AF-S as in one of the responses, just so we are talking about the same thing?</p>

<p>Jim</p>

[evannorth]

<p>i have the 105 af-d, (and he 60mm af=d).both are classic japanese built, pin sharp lenses. the reduction of maximum aperture is normal at close distance. working distance will remain the same with a TC. magnification at minimum distance will increase. i cant say which TC is usable, but it does state which nikon ones that suit it in the lenses manual. </p>

[ariel_s1]

<p>Whoops, it's probably an AF-D, don't know how that got switched in my head. Sorry 'bout that. In that case, any teleconverter will work, although some of the Ai-s generation teleconverters won't meter with the lower-end cameras. If you have a D200, D300, D7000, or any of the full-frame or professional Nikons, then you'll be fine with whatever.</p>

[sgust]

<p>If my understanding of how a teleconverter works is correct, it takes the light that exits from the central part of the back of the lens and magnifies it. So you get a higher resolution image of the center part of the image that the lens would normally produce. But spreading the light out gives you less of it per pixel. A lot of people will say it shrinks your aperture, but I find that misleading because you may think you'll get the associated DOF with the small aperture. But in reality you get the same DOF that the lens would have without the TC with the amount of light that reaches the sensor reduced. Just something to keep in mind.</p>

[Jerry_]

<p>If you find a tele-converter that will work with the lens, be prepared for a 'no longer f2.8' lens for close-up work. Trying to manually focus at f8, or so (f5.6 with a T/C makes this so....) on a bug will be interesting. Let the lens work without a T/C and you may enjoy using it more.</p>

<p> </p>

[rodeo_joe1]

<blockquote>

<p>"So you get a higher resolution image of the center part of the image that the lens would normally produce. But spreading the light out gives you less of it per pixel. A lot of people will say it shrinks your aperture, but I find that misleading because you may think you'll get the associated DOF with the small aperture. But in reality you get the same DOF that the lens would have without the TC with the amount of light that reaches the sensor reduced."</p>

</blockquote>

<p>- Siegfried, nearly all of that is completely wrong I'm afraid.</p>

<p>A teleconverter will always result in lower resolution, both in the centre of the field and increasingly toward the edges of the frame. It'll also introduce more colour aberration and more geometrical distortion (usually pincushion).</p>

<p>"A lot of people say it shrinks the aperture"; that's because that's precisely what it does. The aperture number of the main lens is multiplied by the same factor as the focal length when a TC is attached. With a 2x converter you lose two stops, and for example an f/4 lens becomes f/8. This isn't a "virtual" thing, the aperture really is reduced, and the focal length really is doubled. Thinking of a TC as "spreading the light out" is what's misleading.</p>

<p>Also, the depth-of-field doesn't stay the same with a TC. You can verify this by using a D-o-F calculator and doubling both the focal length and aperture number for a given focused distance. There's more D-o-F with an unconverted lens than with a TC attached. The reason for this is that D-o-F is affected more by scaling focal length than by a similar change of aperture number.</p>

[sgust]

<blockquote>

<p>A teleconverter will always result in lower resolution,</p>

</blockquote>

<p>If that were the case why would anyone buy a TC? Why not just crop the center section of you image. I can't imagine the results from a crop of an image taken without the converter would show as much detail as one with the converter if they were both focused at the same distance.<br>

And the aperture shrinking? I don't think the TC effects the size of the opening created by the aperture blades. I believe what your talking about is the "effective" aperture, the value you use for calculating exposure. And yes it doubles due the reduction in light intensity at the sensor.<br>

I can't claim to be very knowledgeable about this, but I don't think it reduces DOF. I'm still fairly sure a TC works by magnifying the central section of the image circle so that it covers the entire sensor. By that reasoning shouldn't the DOF remain unaffected?<br>

Maybe I am completely mistaken on whats going on inside a TC. Anyone care to explain it?</p>

[Peter_in_PA]

<blockquote>

<p>If that were the case why would anyone buy a TC? Why not just crop the center section of you image.</p>

</blockquote>

<p>In fact, for many of us, that's exactly what we do. I have only ever owned one TC, and I used it exclusively on an old Vivitar 200mm f3.5 lens. An it gave poor results that way, to be honest.</p>

<p>With the high-res digital cameras of today, MANY lenses give better results if you crop than if you used a TC. TCs make sense on very long very fast lenses, and that's about it.</p>

[elliot1]

<p><em>"</em><em>A teleconverter will always result in lower resolution"</em> No, not ALWAYS. Both Nikon (TC-20E III) and Canon (2.0x III) offer improved TCs that give you improved resolution with the TC as opposed to cropping and upsizing the center section of the image.</p>

[ariel_s1]

<p>Sigfried, you are right that the TC doesn't <strong>affect</strong> (not effect) the physical size of the opening created by the aperture blades. However, given that the f-number is not a concrete number, but a RATIO of focal length to pupil diameter, then even though the diameter doesn't change, the ratio, and therefore the f-number, does. If you "can't claim to be very knowledgeable about this," then you should do some quick google searching before you state your arguments. A teleconverter will absolutely change the depth of field. A 105mm f/2.8 lens with a 1.4x teleconverter will have the DOF of a 147mm f/4 lens. not of a 105mm f/2.8 lens. Feel free to do all the google searching you want to verify this.</p>

[alan_olander1664878205]

<p>A TC will lower the resolution of a lens, but it will be less than what a crop would do.<br>

A 105mm with a 1.4 TC will:<br>

1) be a 147mm lens<br>

2) have the DOF of a 147mm lens<br>

3) have a maximum f/stop of f/4 (as Ariel explained)<br>

4) have a greater working distance than the 105mm by itself at the same magnification<br>

5) have greater magnification at the lens' closest focusing distance than the 105mm by itself</p>

[sgust]

<p>Thanks for the clarification. And yes Ariel your right, maybe I aught not to have hijacked this thread, sorry Mark, to get some explanation on TCs. But Google gave me a lot of mixed information especially about the DOF and the resulting resolution using a TC.</p>

 

[nigel_deacon]

<p>I would like to add an important correction. The responses above include phrases like: -<br>

"<em>you'd want the newer teleconverters such as the TC-14E II</em>" and, "<em>in that case, any teleconverter will work</em>." <br>

This is incorrect, and could lead someone into making an expensive mistake. The Nikon TC-14E/EII, and "E" versions of the TC-17 and TC-20 ONLY WORK WITH AF-S LENSES. You would need to use an independent such as the Kenko teleconverter. <br>

My 105mm AF-S VR produces fairly decent results with the TC-14EII, but the lens is noticeably sharper without it - so I never use this combination (I've never tried my TC-20EIII on it). The Nikon converters are optimized for use on longer telephoto lenses. </p>