Sigma 85mm 1.4 - When?

[joseph_wisniewski]

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<p>Nikon apparently have a patent on a 85/1.4 with VR (mentioned on the rumor site).</p>

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<p>Nikon also has a patent for a 1.4x TC with built in VR, and a 1:1 "relay lens" with VR that looks like a TC. Those are "preemptive patents". And, as you pointed out, it's that highly accurate "rumor site".</p>

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<p>Also, the existing 200/2 has VR.</p>

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<p>OK, you've got me on that one. The 200mm f2 has a long enough optical path and the proper positive/negative group pairings to accommodate VR. I still don't think they can do it with the 85mm f1.4. It lacks that pairing (it's not really a telephoto, more like an 85mm normal) and it's dang near solid, the way the elements are packed together.</p>

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<p>Well, the 105 VR is generally considered to be an inferior macro lens to its predecessor, at least as far as sharpness goes. The VR version is superior at portrait distances though, and has much nicer bokeh.</p>

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<p>Exactly!</p>

<p>That's not evidence that VR compromises a lens, though. It's evidence that trying to make a "one size fits all" lens compromises a lens. They made it a better portrait lens (although not as good as a 105mm f2.0 DC or a 105mm f2.5 Ai-S) and this greatly compromised the macro performance. (you state all that, also, but I thought I'd paraphrase)</p>

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<p>If Nikon makes an AF-S version of the 105DC without VR</p>

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<p>I believe that if they recast the 105 DC, it will, indeed, be without VR. For much the same reasons as I stated for the 85mm. The 105mm is a pretty solid chunk of glass, and its design isn't very VR friendly. I can see them bringing in some ED elements to address the longitudinal CA, but the optical design is already AF-S friendly. The original 85mm f1.4 Ai was unit focusing, it needed a rear focusing redesign for AF-S.</p>

<p>Even the 135mm f2.0 DC isn't as VR friendly as the 200mm.</p>

<p> </p>

[joseph_wisniewski]

<p>You know, I must have the weirdest 135mm f2.0 DC on the planet, because if I set the DC collar 1/2 notch right of center, and then adjust the AF fine tuning, the thing focuses well enough to shoot sports with it.</p>

[anthony_bez]

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<p>Do you have any evidence to support this? I've seen several lenses replaced by VR models that substantially increased image quality. My experience with the 70-200mm f2.8 VR and its predecessor, the 80-200mm AF-D two ring shows that the VR lens is optically quite superior to the older lens.</p>

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<p>My point was that the VR function affects the IQ and out of focus rendition when used. <strong>My use</strong> with the 85mm f1.4 does not require VR so it is of no interest <strong>to me</strong>.</p>

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<p>Typically not so for large, heavy lenses. The AF-S mechanism lets you put the focus motors close to the focusing elements, saving very expensive gearing and complex mechanical A/M clutches. Several of the AF-S lenses are actually slightly smaller and lighter than their "screwdriver" AF predecessors. The 85mm f1.4 has a rather large "empty zone" surrounding the rear 1/3 of the lens. The internal design is more like a truncated cone, about 75mm at the front, 50mm at the camera end. That would make for a very ugly lens (like some large format lenses) so the outer shell holds maintains the 80mm diameter for most of the lens's length. Plenty of room in thatempty space for an AF-S motor.</p>

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<p>Then I may well be wrong but all the AF lenses I have replaced with AF-S versions have been bigger. For example 80-200 f2.8, 300 f4, 50mm f1.4.<br /> Personally an increase in size if needed is acceptable because AF-S would be useful<strong> to me</strong></p>

[joseph_wisniewski]

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<p>My point was that the VR function affects the IQ and out of focus rendition when used.</p>

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<p>And mine is that there is no evidence to support that.</p>

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<p>Then I may well be wrong but all the AF lenses I have replaced with AF-S versions have been bigger. For example 80-200 f2.8, 300 f4, 50mm f1.4.</p>

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<p>You're mixing cause and effect. All of the lenses you site underwent radical redesigns, with major improvements that have nothing to do with them being AF-S versions.</p>

<ul>

<li>300mm f4 went from 8 elements to 10. The redesign included an improvement in close focusing ability from 2.5m (1:7.1x) to 1.45m (1:3.7x). That's pretty good for a lens that got "bigger" by about 1% (diameter increased from 89mm to 90mm, length increased from 227mm to 230mm).</li>

<li>50mm f1.4 went from 7 elements to 8 elements in 7 groups. They widened the optical path and shifted the exit pupil forward, and that increased the filter size to 58mm. The new design has lower distortion, lower chromatic aberration, better bokeh, and better sharpness wide open than its predecessor.</li>

<li>80-200mm f2.8 went from 18 elements to 18, and from 3 ED elements to 5. The new lens has improved contrast, sharpness, and chromatic aberration.</li>

</ul>

<p>I'm glad you picked the 80-200mm f2.8 as an example.<br>

Back in the manual focus days, the 80-200mm f2.8 had another redesign, from 12 elements to 15. This also increased the weight and size of the lens a bit, but had nothing to do with a change in the focusing mechanism.<br>

This has been happening in lens design for many decades. My AF 200mm f4 micro-Nikkor is considerably larger and heavier than the Ai version that preceded it. It also went from 9 elements to 13, and gained the ability to go down to 1:1 in without tubes or teleconverters.<br>

The AF 28mm f2.8 had a radical redesign, 5 elements up to 6, greatly increased sharpness. Size and weight also went up. This happened at the same time Nikon was revising the AF system to incorporate their "D" type distance information. So, one might assume that the D update had something to do with the increased size and weight, but it didn't. None of the other AF lenses to get a D update that year got larger or heavier, and none of them had an optical redesign that increased the number of elements or the size of the lens.</p>

[anthony_bez]

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<p>And mine is that there is no evidence to support that.</p>

 

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<p>I fully accept your view on VR but my experience differs...<br>

I have obtained undesirable out of focus rendition when using VR, and I believe IQ in my images is affected. <br>

I only say for my use with this lens VR does not interest me. I am sure other people would want this feature. </p>

 

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<p>You're mixing cause and effect. All of the lenses you site underwent radical redesigns, with major improvements that have nothing to do with them being AF-S versions.</p>

 

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<p>Then I am wrong...... But adding a focus motor to a lens is likely to increase the size.</p>

[joseph_wisniewski]

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<p>I fully accept your view on VR but my experience differs...</p>

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<p>And I accept that your view and experience differs from mine. Peace</p>

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<p>But adding a focus motor to a lens is likely to increase the size.</p>

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<p>That is where life gets really, really weird. Focusing lenses, in general, is not easy. For auto focus lenses, you need a mechanism that connects to the Nikon "screwdriver" system.If your lens design needs its focusing elements far from the rear of the lens, you then have linkages from the screwdriver to where the focusing elements are. If the focusing elements move when zooming, then this mechanism also needs to be able to transmit small, precise focus motions along a sliding linkage, to get to wherever the focusing has to happen.</p>

<p>Just to make matters worse, the screwdriver is a radius of about 25mm from the lens center line.If you want to focus something larger than 40mm in diameter, you now need to have a link shaft, gears to move to a different radius, and then a second link shaft. The most complex AF screwdriver lens I've seen had three link shafts and a sliding shaft about 75mm (3 inches) long.</p>

<p>There's also a mechanical focusing collar, and a either cam (a curved "track" on a tube that surrounds the insides of the lens) or more link shafts that connect the focus collar to the A/M clutch, and then back to the focus mechanism. I have owned five Nikkors with that mechanism, the 85mm f1.4, 135mm DC, 60mm f2.8 micro, 200mm f4 micro, and 80-200mm f2.8 two collar. Only one of the five has not failed: the 85mm f1.4. The A/M collar also draws in a friction clutch mechanism to provide a "nice" manual focus feeling.</p>

<p>The ultrasonic ring motor is a marvel of engineering. It's literally a "friction motor". There are no bulky, heavy magnets, just a collar of plastic and light ceramic that turns vibration into motion (skip and stop, skip and stop). It weighs about as much as the mechanism that provides the nice manual focus feel in lenses like the 85mm f1.4, because that's what it is, just a big friction clutch. It can be placed anywhere in the lens. If you want a front focus design, like the 17-35mm f2.8 AF-S, you just do it. If you want to really simplify the lens, you can link the mechanical focus collar directly to the ultrasonic friction motor. It's more common to use a three roller planetary system, because that keeps the collar from rotating while the lens is being autofocused, but lets you manually focus right through the running motor.</p>

<p>So, by the time you get rid of the link shafts, coupling gears to change the shaft center line, the A/M mechanism, you're left with something pretty small.</p>

<p>The only time a lens gets larger because they add AF-S (not the situations I mentioned earlier, where the lens gets a more complicated optical formula at the same time it gets an AF-S revision) is when the lens has no A/M mechanism to start with, and it has a rear focusing or small unit-focusing mechanism. I look at the focus mechanism on my old 70-210mm f4-5.6 (yes, I still use it sometimes. It's an old friend) and think how much more compact it could be without that stupid sliding AF link shaft.</p>

[emiliogtz]

<p>We went off-topic, but still, this has been a very nice thread to follow.</p>

<p>Does anybody remember (if it was ever known) why it was that after flirting with motors on the lenses, before Canon, did Nikon choose to go with the "screwdriver" AF mechanism?</p>

<p>I think economics had something to do with it, but was it just that?</p>

[joseph_wisniewski]

<p>Pretty much a combination of two reasons. First, as you said, was economics. Spend X dollars on one really good motor, and all the lenses get that good motor.</p>

<p>The second reason was that when Nikon launched the first AF system, the piezo motor wasn't really a mature technology, and Nikon used a high speed electromagnetic motor, geared down to focusing speed and torque. This was awkward on small lenses, it really did require a diameter increase (or a "lump" in the lens casing where the motor was.</p>

[anthony_bez]

<p>Joseph,<br>

Thank you for your fascinating in-depth explanation I now fully understand your point.<br>

Unfortunately I still have two lenses (80-200mm, 85mm) on your list of impending AF failure!<br>

Best Regards</p>

<p>Emilio,<br>

I would not worry about it going "off-topic" I think we are the only one's left in the room. I have also enjoyed Joseph's lens design master-class.</p>

[tom_kay]

<p>Joseph, thanks a lot for your very interesting posts. I learned from them.<br>

I'd really like to see some images from the Sigma 85/1.4.<br>

I could imagine they've created a very fine lens, but I'm not a 100% confident they managed it.</p>