Author Topic: Rorslett's Rule and Short Telephotos for the Df  (Read 12697 times)

Roland Vink

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Re: Rorslett's Rule and Short Telephotos for the Df
« Reply #60 on: April 15, 2019, 23:43:54 »
When choosing lenses I tend to grab a 50mm lens first, and then add a 28 or 24 as a wider companion, and 105 or 135 as a telephoto. I tend to skip 35mm and 85mm lenses, not that I have anything against them, but the focal length is too close to provide a useful spread of lenses.

On the other hand, taken in isolation the 85mm is an excellent lens and it nicely compliments the 35mm focal length. The 85/2 is very compact, hardly bigger than most manual focus 50mm lenses, and much smaller than the current AF 85/1.8 options. Some reviews say the AI 85/2 has rather low contrast, which was intentional to make it more flattering for portraiture (but less suitable for general use). My AI-S copy, which supposedly has the same optics seems as sharp and contrasty as my other AI-S lenses so maybe the coatings were improved? Performance is about the same as my AI 105/2.5 although I haven't done any close side by side comparisons. I'd say the rendering of the 105 is slightly "rounder". Ric Haw has some useful comments on his blog:
https://richardhaw.com/lens-repair-articles/

I prefer the AI-S 85/2 over the AI. The focus throw of the AI version is too long so focusing is very slow, the focus throw of the AI-S is better balanced. The AI-S also looks nicer. Given the small size, good performance and relatively low cost, why not try one? I have one for sale if you are interested (some years ago I bought a spare copy but I don't really need it)

Jacques Pochoy

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Re: Rorslett's Rule and Short Telephotos for the Df
« Reply #61 on: April 16, 2019, 00:53:30 »
After my Leica M era, I used to prefer the 35mm-50mm-85mm combo (I've never been a fan of "wide" ). Since I've bought the 28mm/2.8 AI-s and the 105mm f/2.5 AI-S I tend to use them more but still often return to the 85mm/2 AI, the 35mm/2 O.C and the good old 50mm f/2 AI. I do find a real difference between these focal lengths, even if I understand the 24 or 28-50-105 theory  ;)
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Akira

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Re: Rorslett's Rule and Short Telephotos for the Df
« Reply #62 on: April 16, 2019, 02:18:17 »
I prefer the AI-S 85/2 over the AI. The focus throw of the AI version is too long so focusing is very slow, the focus throw of the AI-S is better balanced. The AI-S also looks nicer. Given the small size, good performance and relatively low cost, why not try one? I have one for sale if you are interested (some years ago I bought a spare copy but I don't really need it)

Roland, if you use the live view more often or a mirrorless camera, you would appreciate the longer focus throw of Ai lenses.  During the film days, I was frustrated by the slower focusing of Ai lenses and loved the intuitive rotation/focusing ratio of Ais lenses.  On the other hand, now that precise nailing of the focus is possible on both EVF and LCD, the short focus throw of Ais lenses is simply irritating: the focus changes too fast, and it is difficult to stop at the best focusing point.
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Roland Vink

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Re: Rorslett's Rule and Short Telephotos for the Df
« Reply #63 on: April 16, 2019, 05:52:22 »
Akira, I agree that the longer focus throw of AI lenses is generally preferable. In this case I think the focus throw of the AI 85/2 is too long. The focus ring turns 255 (nearly 3/4 turn) from infinity to the non-macro limit of 0.85m, you need to adjust your grip two or three times to focus from end to end which is inconvenient. The focus throw of the AI-S 85/2 is 170, which I find is very comfortable, and comparable to the Ai 105/2.5 :)

Akira

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Re: Rorslett's Rule and Short Telephotos for the Df
« Reply #64 on: April 16, 2019, 06:09:14 »
Akira, I agree that the longer focus throw of AI lenses is generally preferable. In this case I think the focus throw of the AI 85/2 is too long. The focus ring turns 255 (nearly 3/4 turn) from infinity to the non-macro limit of 0.85m, you need to adjust your grip two or three times to focus from end to end which is inconvenient. The focus throw of the AI-S 85/2 is 170, which I find is very comfortable, and comparable to the Ai 105/2.5 :)

I didn'tr know that the "total" focus throw of Ai 85/2.0 is that long.

Admitting that the rotation of nearly 3/4 turn between 0.85m and infinity is inconvenient, my main concern is the focus throw between 10 meters and infinity which is still too short on the Ais version as a relatively fast mid-tele.  That's why I always prefer Ai versions in general, so long as the optical designs remain the same.

In the closer range, Ais can be more convenient, though.

By the way, I just realized that the focus throw of 200/4.0 is slightly longer on Ais than on Ai.   :o :o :o
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richardHaw

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Re: Rorslett's Rule and Short Telephotos for the Df
« Reply #65 on: April 16, 2019, 14:40:02 »
ladies and gentlemen, the 135mm f/2 Ai  :o :o :o

the solitaire

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Re: Rorslett's Rule and Short Telephotos for the Df
« Reply #66 on: April 16, 2019, 23:21:56 »
As far as rules go, in recent times I tend to put the 35mm f2 Nikkor-O in my camera bag a lot along with the 300 f2,8 Ai-S. Which rule does that comply with? Works for me either way ;)
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Roland Vink

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Re: Rorslett's Rule and Short Telephotos for the Df
« Reply #67 on: April 16, 2019, 23:24:15 »
I didn't know that the "total" focus throw of Ai 85/2.0 is that long.

Admitting that the rotation of nearly 3/4 turn between 0.85m and infinity is inconvenient, my main concern is the focus throw between 10 meters and infinity which is still too short on the Ais version as a relatively fast mid-tele.  That's why I always prefer Ai versions in general, so long as the optical designs remain the same.

In the closer range, Ais can be more convenient, though.

By the way, I just realized that the focus throw of 200/4.0 is slightly longer on Ais than on Ai.   :o :o :o
The focus throw of the AIS and AI 200/4 is the same (205) :)
There are a few AIS lenses with a longer focus throw than the AI counterparts, so sometimes the AIS is the preferred version:
- AIS 35/2.8 (120) vs AI (100), although the earlier AI version is even longer (195) and probably better optically
- AIS 180/2.8 ED (190) vs AI (170)
- AIS 300/4.5 (180) vs AI (150), although that is due to the closer focus limit.

As for the AIS 85/2, I find the focus throw near infinity is adequate, but I agree it would be nice if were longer - focusing in this range is surprisingly difficult as even a small movement of the focus ring will shift focus a long way and it's not always obvious in the viewfinder. Especially since shots near infinity are often landscapes where critical sharpness is important.

This is a consequence of linear helical focusing - the range near infinity is bunched up while the close range is very spread out. To solve this problem you would need to have a non-linear focus cam to even out the focus range, but cams tend to be harder to manufacture and more prone to sample variation so are not used except for zooms and some specialist lenses.

Or how about a lens with two focus rings? One for fast focusing from near to far, the other for fine tuning, which would be useful for critical focus near infinity, and at close range could be good for focus stacking etc.

Lenses where the focal length changes while focusing can also spread out the focus scale more evenly. For example, AIS 105/4 micro and 105/2.8 both have the same focus throw (300) from near to far, and both achieve the same magnification at close range (1:2). However the f/2.8 needs to focus closer (0.41m vs 0.48m) to get there because focal length reduces at close range due to CRC. Both have the same focus throw near infinity, but at close range the focus throw of the f/2.8 is more compressed compared to the f/4 version. The same effect could be used to even out the focus scale for non-macro lenses, although the effect is not very noticeable and probably not worth the effort unless there are some other benefits such as improved near-far optical performance.

Roland Vink

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Re: Rorslett's Rule and Short Telephotos for the Df
« Reply #68 on: April 16, 2019, 23:26:27 »
As far as rules go, in recent times I tend to put the 35mm f2 Nikkor-O in my camera bag a lot along with the 300 f2,8 Ai-S. Which rule does that comply with? Works for me either way ;)
That appears to be the "solitaire 8x ratio between lens" rule :) :o

Akira

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Re: Rorslett's Rule and Short Telephotos for the Df
« Reply #69 on: April 16, 2019, 23:50:04 »
The focus throw of the AIS and AI 200/4 is the same (205) :)
There are a few AIS lenses with a longer focus throw than the AI counterparts, so sometimes the AIS is the preferred version:
- AIS 35/2.8 (120) vs AI (100), although the earlier AI version is even longer (195) and probably better optically
- AIS 180/2.8 ED (190) vs AI (170)
- AIS 300/4.5 (180) vs AI (150), although that is due to the closer focus limit.

As for the AIS 85/2, I find the focus throw near infinity is adequate, but I agree it would be nice if were longer - focusing in this range is surprisingly difficult as even a small movement of the focus ring will shift focus a long way and it's not always obvious in the viewfinder. Especially since shots near infinity are often landscapes where critical sharpness is important.

This is a consequence of linear helical focusing - the range near infinity is bunched up while the close range is very spread out. To solve this problem you would need to have a non-linear focus cam to even out the focus range, but cams tend to be harder to manufacture and more prone to sample variation so are not used except for zooms and some specialist lenses.

Or how about a lens with two focus rings? One for fast focusing from near to far, the other for fine tuning, which would be useful for critical focus near infinity, and at close range could be good for focus stacking etc.

Lenses where the focal length changes while focusing can also spread out the focus scale more evenly. For example, AIS 105/4 micro and 105/2.8 both have the same focus throw (300) from near to far, and both achieve the same magnification at close range (1:2). However the f/2.8 needs to focus closer (0.41m vs 0.48m) to get there because focal length reduces at close range due to CRC. Both have the same focus throw near infinity, but at close range the focus throw of the f/2.8 is more compressed compared to the f/4 version. The same effect could be used to even out the focus scale for non-macro lenses, although the effect is not very noticeable and probably not worth the effort unless there are some other benefits such as improved near-far optical performance.

Roland, thank you for confirming the focus throw of 200/4.0.

I completely agree with you in terms of the cons of the linear helicoid.  It's shame that Nikon didn't employed the non-linear cam system on their IF telephoto lenses.  And, yes, the all-too short focus throw for the distance on Micro Nikkors are notorious, which prevents them from being true all rounder, at least to me...
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Kenneth Rich

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Re: Rorslett's Rule and Short Telephotos for the Df
« Reply #70 on: April 17, 2019, 04:13:58 »
I am adopting Rorslett's Rule and it has saved me money and extra baggage already!  In addition to dropping the idea of getting the 85mm, I'm also dropping my plan to buy a twenty mm to replace the one I sold forty years ago!  Long live Rorslett's Rule!  Thank you. I need fewer lenses, not more.

Airy

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Re: Rorslett's Rule and Short Telephotos for the Df
« Reply #71 on: April 17, 2019, 05:19:27 »
The Zeiss MP 50/2 suffers from the same issue - very short throw between 5m and infinite, very long throw at close range. Usability at long distances is however saved by the relative stiffness of the focussing, combined with total absence of dry friction or slack in the helicoid. It comes at a high price (narrow manufacturing tolerances...) and may degrade with time though.
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the solitaire

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Re: Rorslett's Rule and Short Telephotos for the Df
« Reply #72 on: April 21, 2019, 11:49:18 »
That appears to be the "solitaire 8x ratio between lens" rule :) :o

It's more like the "Solitaires, whatever you do, bring a 300 f2,8" rule :)

I would not mind the 8x ratio between lens rule either, but with the 55mm I would have to bring a 400mm f3,5, which I do not yet own ;)

Now if anyone would be willing to trade my 300 f2,8 for a 200 f2, I could adhere to Bjorns rule and bring a 55 f1,2 or f3,5, the 105 f2,5 and 200 f2. Any takers? :D
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