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adjusting lenses for infinity
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Have you had a manual focus lens adjusted for infinity?
Yes, I have
25%
 25%  [ 5 ]
Yes, and I found it improved results noticeably
20%
 20%  [ 4 ]
Yes, but I did not find it impacted results
10%
 10%  [ 2 ]
No, I have not
45%
 45%  [ 9 ]
Total Votes : 20



PostPosted: Wed May 16, 2012 9:46 pm    Post subject: adjusting lenses for infinity Reply with quote

Through my personal as well as the business I run I have access to hundreds of lenses, which I believe gives me a sample n of sufficient validity. I have in my years as a photographer found that lemons ie. bad copies of a lens do exist, and there is no doubt that lens manufacturers define "within factory tolerances" differently. (Which is why I stay clear of certain lens manufacturer's products.) The issue of lemon copies in my opinion is largely overstated however, as I believe there are multiple times more lemon photographers than lemon lenses. OK, so much for new lenses - this post is about aging manual focus lenses and how they wear.

Fact is: All lenses wear over time, they get banged and lens elements become misaligned, they dry out, focusing helicoids are worn and this affects lens accuracy. As an example, here are three copies of what optically is the same lens (though the Nikkor 50/1.2 Ai diaphragm has 7 rounded blades vs. Ai-S with 9 straight blades). My photo and my lenses yes, didn't steal someone's work. These are all exposed at f/1.2 and distance to subject is near infinity (Live View used).



This is a lens that has a focusing mechanism that stops at infinity, and I prefer that it stops where I want it to - at infinity. I know many photogs like their lenses to overfocus - I don't. Adjusting those three Nikkor 50/1.2 Ai/Ai-S copies cost me about 50 EUR each, so if you own a considerable amount of old glass (as many of us do), there is potentially a big cost involved. Results however were well worth the effort and money. After these lenses had been calibrated for infinity, they also showed less vignetting wide open, less CA overall and improved contrast and detail also at close focus.

Most of the fine-tuned focus error with lens samples is hidden when used on smaller (especially crop frame) sensors. You can't really say if a lens performs at its best until you combine it with a sensor that resolves more detail than the lens can.

Now that I have used the 36 megapixel D800 since early April I am considering taking some of my lenses for infinity calibration. This however is not a straight-forward solution for me as I live in a country where annual temperature changes from -35C to +35C. When nitpicking about detail at infinity one should remember that small factors as temperature changes can (and do) affect infinity. (The longer the lens and the shallower depth of field, the more likely you will notice this.)

More examples: The Voigtländer 75mm f/2.5 Color Heliar (Nikon Ai-S) has a mechanical flaw that with time loosens (and unscrews) the focusing ring. Unscrewing the focusing ring is the first stage of lens disassembly, and thus a loose focusing ring affects lens elements. This is easy to fix, a qualified repairman will add a notch and stopper to the thread and a drop of glue in the right place will cure all problems.

Result: What was sold on eBay for half the going rate (lemon copy sold cheap) was fixed for 50 EUR to be an excellent sample. I have more examples, any lens of a type that focuses by moving the whole lens assembly will most likely greatly benefit from adjustment, if the lens has been used for more than 10 years.

What are your thoughts on the subject?


PostPosted: Wed May 16, 2012 10:05 pm    Post subject: Reply with quote

I agree about what you say. In most cases a lemon copy is such because miscalibrated or because a previous user messed with it.
I feel differently about infinity though. When using my digital SLRs I like it when my lenses do exceed infinity a little, even if I would never adjust them that way voluntarily.
This because adapters may vary and the cameras themselves have little differences, plus over time as you noted the focus position may shift. A little beyond infinity allows for that critical margin.
Of all the possible focusing options, infinity is the one that requires less changes on the fly. I mean that you rarely have to rush to focus on infinity, because by nature, infinity aims at very distant things,
so unless you are focusing on a rocket Wink you usually have the time to adjust with liveview.


PostPosted: Wed May 16, 2012 10:17 pm    Post subject: Reply with quote

I never find a lemon lens
I needed to fine adjust 2 of my lenses, the others were perfect
http://forum.mflenses.com/infinity-tune-for-contax-lens-t7011.html


PostPosted: Wed May 16, 2012 11:10 pm    Post subject: Reply with quote

On any camera, the infinity focus adjustment margin of error is much less for wide angle lens than for telephoto. This fact does compensate some for less thermal expansions due to being smaller.

I know that focus on mountain 50km from here is different from focus on mountain nearly 80km from here, and focus on moon too! I have a nice 500mm lens that I think does not quite reach infinity. Close but not quite. I plan to adjust it myself.

Some money could be saved I think if there were some easy way to check for infinity focus. The telescope folks have methods, such as using a mask with two holes in it over the lens, focus on a bright star, when images from each hole align, lens is focused on that star -- I don't think even that far is quite to infinity. Laughing Wink


PostPosted: Wed May 16, 2012 11:14 pm    Post subject: Reply with quote

I have had a lemon, a Vivitar Series 1 2.3/135 that was real garbage. I have had other bad lenses but never was sure if they were lemons or just crappy lenses to begin with. Other people had good results with the Viv 2.3/135 so I reckon mine must have been a lemon.

Seems to me, the major manufacturers had sufficiently good quality control for it to be hard to find a lemon, but once you step into third-party brands the QC drops off and there are lemons to be had.

I think what orio says about bad copies usually being due to someone having messed with them also rings true.


PostPosted: Thu May 17, 2012 12:44 pm    Post subject: Reply with quote

iangreenhalgh1 wrote:
I think what orio says about bad copies usually being due to someone having messed with them also rings true.


In 2008, I bought a Nikkor 24-70/2.8G AF-S straight off the quality control line and from day 1 I was startled by how good the lens was. In the spring of 2012 I noticed on one wedding shoot that the lens had problems with acquiring focus and also delivered soft images. I took the lens to service and asked their opinion, saw when they attached it to an electronics bench and did optical tests to it. Diagnosis: one misaligned element, likely due to the lens sustaining a hit at some point.

Repair cost: 823 EUR, because rather than disassembling 15 elements in 11 groups they replace the whole inner barrel with a new lens module. In other words, factory refurbished and except outside barrel a completely new lens. New lens costs 1700 EUR so I decided to have it repaired, especially that I had paid only 800 EUR for the 24-70/2.8 when new (benefits of visiting the factory in Japan). Lens works as new now, delivering excellent results.

Now, given this background, I think 50 EUR/lens is a reasonable price for having the lot adjusted - I have in my personal collection more lenses than I care to count and I think maybe 15% of them may need adjustment to perform up to factory standards.


PostPosted: Thu May 17, 2012 12:46 pm    Post subject: Reply with quote

poilu wrote:
I never find a lemon lens
I needed to fine adjust 2 of my lenses, the others were perfect
http://forum.mflenses.com/infinity-tune-for-contax-lens-t7011.html


I have never found a bad copy from Zeiss, but then again I have always bought them new.


PostPosted: Thu May 17, 2012 1:13 pm    Post subject: Reply with quote

Simply adjusting the focus at the infinity stop cannot improve performance. All you are doing is moving the lens block in relation to the mount face. If the lens has a flaw this may become less obvious at perfect focus, visible CA for example, but the flaw will still be there. I don't think there would be any benefit to the faulty Nikkor examples above. My guess is the 50 Euros included more work than simple calibration.


PostPosted: Thu May 17, 2012 3:03 pm    Post subject: Reply with quote

+1 to that. Focus is focus. If the lens is focused on the GG, it doesn't matter what number shows up on the ring. Your example looked like mine look before and after cleaning. My local place won't do just one thing--if they get a lens to fix they make it RIGHT everywhere--they don't want to be blamed for the thing they didn't do.

The one place you can have problems that I don't think anyone realized is with mirror placement. If the mirror isn't stopping in the right place, that can throw everything off. I've had the Nikon authorized service set all my lenses spot on at infinity. Then if the finder doesn't focus right at infinity, I start adjusting the mirror. That's something you should notice, though, in pixel peeping: if you consistently focus behind or in front of where you intended, at every distance with every lens, that's the mirror.


PostPosted: Thu May 17, 2012 6:51 pm    Post subject: Reply with quote

Esox lucius wrote:
iangreenhalgh1 wrote:
I think what orio says about bad copies usually being due to someone having messed with them also rings true.


In 2008, I bought a Nikkor 24-70/2.8G AF-S straight off the quality control line and from day 1 I was startled by how good the lens was. In the spring of 2012 I noticed on one wedding shoot that the lens had problems with acquiring focus and also delivered soft images. I took the lens to service and asked their opinion, saw when they attached it to an electronics bench and did optical tests to it. Diagnosis: one misaligned element, likely due to the lens sustaining a hit at some point.

Repair cost: 823 EUR, because rather than disassembling 15 elements in 11 groups they replace the whole inner barrel with a new lens module. In other words, factory refurbished and except outside barrel a completely new lens. New lens costs 1700 EUR so I decided to have it repaired, especially that I had paid only 800 EUR for the 24-70/2.8 when new (benefits of visiting the factory in Japan). Lens works as new now, delivering excellent results.

Now, given this background, I think 50 EUR/lens is a reasonable price for having the lot adjusted - I have in my personal collection more lenses than I care to count and I think maybe 15% of them may need adjustment to perform up to factory standards.


That's shocking that the lens lasted only 4 years imho. Just shows how build quality has fallen so much, compared to old lenses the modern ones are junk in terms of the strength of the build, sadly.


PostPosted: Thu May 17, 2012 8:39 pm    Post subject: Reply with quote

peterqd wrote:
My guess is the 50 Euros included more work than simple calibration.


Very possible, results however were greatly improved and from three inconsistent samples I now have three lenses which perform identically.

iangreenhalgh1 wrote:
That's shocking that the lens lasted only 4 years imho. Just shows how build quality has fallen so much, compared to old lenses the modern ones are junk in terms of the strength of the build, sadly.


I divide lenses into two categories: A) workhorses (AF lenses) and B) brushes (MF lenses for slow photography)

If you knew me personally you would know that I subject my workhorses (AF-S lenses) to very extreme conditions, while I treat the discontinued MF lens designs with meticulous care.

AF-S lenses I use have been 20m below the surface underwater, highest I have taken some is 4280m, temperature differences from Sahara +50C to Finland -35C. Plus, I shoot about 30 weddings every year and documentaries aren't exactly nice on the equipment, despite good protective bags. I can't tell the exact moment that damaged the 24-70/2.8G permanently but I remember it receiving several hits and dings during its four year career... My D3 is so worn that Nikon's product manager in Finland one time jokingly asked if they could buy it back and put it up for display - despite serious cosmetic wear it still functions to factory standards.


PostPosted: Sat May 19, 2012 8:01 pm    Post subject: Reply with quote

Infinity calibration I did on my own (by trial and error) a couple of times (on adapted lenses - or when an adapter was not precise enough)... and got satisfying results. I had a version of Pentacon 200mm f4 that was soft at infinity as your samples and sharp when calibrated - but that a f4 lens... f1.2 has other abberations...it's impressive that just the misaligned infinity focus is the reason for softness.
But I don't quite understand how this calibration could affect lens performance at closer focus if the aligment is not calibrated (or some other parameters - distance between elements maybe?). I doubt that somebody would calibrate that for 50€, especially in finland?


PostPosted: Sat May 19, 2012 9:28 pm    Post subject: Reply with quote

Good to know it worked well for 4 years of abuse then Smile


PostPosted: Mon May 21, 2012 9:11 pm    Post subject: Reply with quote

peterqd wrote:
Simply adjusting the focus at the infinity stop cannot improve performance. All you are doing is moving the lens block in relation to the mount face. If the lens has a flaw this may become less obvious at perfect focus, visible CA for example, but the flaw will still be there. I don't think there would be any benefit to the faulty Nikkor examples above. My guess is the 50 Euros included more work than simple calibration.


+1


PostPosted: Mon Sep 24, 2012 1:43 pm    Post subject: Reply with quote

I thought this thread was going to be more how to, so I'll search for more, but will ask here anyway. I have just acquired a lens I've been after for quite a while - a near mint copy of Topcor Auto RE 100/2.8, but immediately discovered it is way off infinity. Is the infinity adjustment method pretty consistent between lenses? I have little time to do this as I need (want) to have the lens available in three days.


PostPosted: Mon Sep 24, 2012 1:57 pm    Post subject: Reply with quote

woodrim wrote:
I thought this thread was going to be more how to, so I'll search for more, but will ask here anyway. I have just acquired a lens I've been after for quite a while - a near mint copy of Topcor Auto RE 100/2.8, but immediately discovered it is way off infinity. Is the infinity adjustment method pretty consistent between lenses? I have little time to do this as I need (want) to have the lens available in three days.


Many of the lenses I adjusted, luckily, had some screws that coupled the ring with the focus distance marks with the optical group: in this case it's enough to set the lens at infinity, unscrew those, turn the uncoupled marked ring and re-screw everything.
In some cases these screws are under the rubber grip (e.g. MIR 24, Zenitar 16mm) in others are inside the lens, behind the front element (some smc takumar wides).

On my auto takumar 2.3/35, it was quite a mess: I actually don't know/remember how I did it, but it had something to do with moving a bit a small cone containing the back elements.

Hope this helps.


EDIT
I forgot to mention the quick and dirty way: sanding down the adapter.
It was the first solution I adopted, and it's the way I use lenses before I figure out how to adjust them.
It requires some tools, a suitable workspace, trial-error, and an expendable adapter, though.


PostPosted: Thu Sep 27, 2012 8:49 am    Post subject: Reply with quote

Just to add a point. When I had my film equipment for Pentacon Six I did some servicing for a few very old lenses and in a process found out that pretty much all of them focused slightly past infinity. I adjusted one of them initially (Vega 12b) to stop precisely at infinity and it was sort of fine until one day i discovered that it does not go to infinity anymore. I readjusted it back and after doing some research found out that it is done on purpouse. In a lenses with fully metal construction the metal can expand contract very slightly with temperature variations. This though microscopic does affect the focusing helicoid threads which in MF lenses are very fine to allow long turns and precise manual focus as a result the infinity focus tend to float a bit. So the lens manufacturers of old time were leaving a tiny amount of turn after infinity to cater for this - this is especially the case on a lenses that allow near 360 degrees turns for focusing.

So I would not encourage people to set their MF lenses to stop precisely at infinity as this mark may change.


PostPosted: Thu Sep 27, 2012 8:59 am    Post subject: Reply with quote

AlexeyD wrote:
Just to add a point. When I had my film equipment for Pentacon Six I did some servicing for a few very old lenses and in a process found out that pretty much all of them focused slightly past infinity. I adjusted one of them initially (Vega 12b) to stop precisely at infinity and it was sort of fine until one day i discovered that it does not go to infinity anymore. I readjusted it back and after doing some research found out that it is done on purpouse. In a lenses with fully metal construction the metal can expand contract very slightly with temperature variations. This though microscopic does affect the focusing helicoid threads which in MF lenses are very fine to allow long turns and precise manual focus as a result the infinity focus tend to float a bit. So the lens manufacturers of old time were leaving a tiny amount of turn after infinity to cater for this - this is especially the case on a lenses that allow near 360 degrees turns for focusing.
So I would not encourage people to set their MF lenses to stop precisely at infinity as this mark may change.


That happened to me as well on the first lens on which I adjusted infinity. I thought it was because of my error. Since then, I tend to not adjust lenses going slightly past infinite anymore.
Another case: I got my excellent looking MIR 24 N some weeks ago: I shot it mostly at f5.6/8 because it was sunny those days.
Last week i took some photos at night, in which I needed to focus at infinity wide open (I know it doesn't happen often, but..) and they looked unsharp. My AF confirm adapter told me that the small things far away were on focus, so I just thought the lens was unsharp wide open focusing far away. But then I tried to adjust infinity, allowing it to go slightly further, and I found out that actually it wasn't reaching it by very little.
Now it delivers much better images in these particualr cases, and I am even happier about my lens.
So, while it's nice having infinity right there where it should be, I think it's even nicer being able to tell that the pic is out of any doubts at the best sharpness possible.


PostPosted: Thu Sep 27, 2012 9:37 am    Post subject: Reply with quote

Aanything wrote:
But then I tried to adjust infinity, allowing it to go slightly further, and I found out that actually it wasn't reaching it by very little.


Yep - that's how it happened to me. What surprised me how far it could vary on those old lenses with long focus turn - my Vega 12b was nearly 360 degree focus turn and the infinity varied considerably between summer and winter temperatures.


PostPosted: Thu Sep 27, 2012 10:04 am    Post subject: Reply with quote

Aanything wrote:
woodrim wrote:
I thought this thread was going to be more how to, so I'll search for more, but will ask here anyway. I have just acquired a lens I've been after for quite a while - a near mint copy of Topcor Auto RE 100/2.8, but immediately discovered it is way off infinity. Is the infinity adjustment method pretty consistent between lenses? I have little time to do this as I need (want) to have the lens available in three days.


Many of the lenses I adjusted, luckily, had some screws that coupled the ring with the focus distance marks with the optical group: in this case it's enough to set the lens at infinity, unscrew those, turn the uncoupled marked ring and re-screw everything.
In some cases these screws are under the rubber grip (e.g. MIR 24, Zenitar 16mm) in others are inside the lens, behind the front element (some smc takumar wides).


That's the method usual for Japanese lenses, but not the only one. Some Zeiss Jena Zebra lenses have a screw that limits the helicoid travel. One adjusts for infinity by screwing it in or out. Every manufacturer does it in his own way, there is no way to be sure until you've taken the lens apart (or read about it somewhere).