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Quick evaluate - how accurate are nikon's specs?
#1
Not sure if anyone can dig up MTF info for the 55/2.8 micro AI-S but I have tested one today.

 

Real focal length: 54.881mm

 

On-axis MTF results:

 

10lp/mm - 90%

 

20lp/mm - astigmatism becomes real - tangential plane at about 86-87% sagittal plane at 70%.

 

30lp/mm - 60% / 55%

 

40lp/mm - about  45% in each plane

 

The field curvature / astigmatism at infinity is "pretty strong" - the two planes peak in MTF almost 100um apart.  In terms of raw values this is quite intense - 100um is almost 20px of blur or so but in terms of the grand scheme of things it is not bad.  .1mm astigmatism is alright - because this is on-axis it points to some misalignment within the lens or tilt in the test system but it is not a bad result.

 

Here is the spot from the lens: http://i.imgur.com/82BxEKE.jpg

 

---

 

To break things down - MTF50% is about 35lp/mm here.  35lp/mm * 2 * 36mm = 2520px of "real resolution" on a full-frame sensor which could realistically be pushed to about 3000px.

#2
testing historic lenses? Introduced in 1979 and a year later updated with the version you tested tells something about how happy Nikon was about it. It's not even listed on Nikon's lens overview. No idea what you expect from those old designs: back in 1980 Nikon were not the best one could get, they were just more affordable. Here's a bit of it's history

 

[Image: MICROGROUPexten.JPG]

 

You won't catch me buying such old glass for a modern camera. Of course, the next comment is only a question of time. "Fabulous lens, I recall me getting great shots out of it" - blah. Back in those film days were better lenses than that one, especially for macro. And those were double or more more expensive.

 

Do you want to counter tests like that one (with MTF Wink )? Are you sure you got a good copy? One thing I learnt from Roger Cicala's MTF experiments: Never trust a single copy. Especially not in museum lenses, I'd like to add.

 

Btw, the only "spec" I read in your post is the focal length. Being only 0.119 mm off their spec is an excellent value. Or do I miss the other specs?

#3
Quote:testing historic lenses? Introduced in 1979 and a year later updated with the version you tested tells something about how happy Nikon was about it.
That is nonsense, really. Nikon replaced the last 55mm f3.5 version with the 55mm f2.8 Ai. Then the transition started going from Ai to Ai-S (every lens went from Ai to Ai-S). The differences between Ai and Ai-S lenses? A little notch on the back plate of the lens for some cameras to change aperture in smaller steps. And some got a cosmetic change, from the "K" style to the Ai-S style. And some got more blades in the aperture like the 50mm f1.2 Ai-S. There was no optical change between the 55mm f2.8 Ai and Ai-S.

Quote:It's not even listed on Nikon's lens overview. No idea what you expect from those old designs: back in 1980 Nikon were not the best one could get, they were just more affordable.
That is not true either. Many Nikkors from the Ai/Ai-S period were very, very good and still are. And Nikkors were never "more affordable", yeah compared to Leica they probably were. Nikon was so happy with the micro-Nikkor 55mm f2.8 Ai-S, that they make and sell it to this day. It is a very good lens, and outperforms many "modern" macro lenses still. The build quality and feel in the focus ring are of very high quality.
http://www.nikonusa.com/en/Nikon-Product...2F2.8.html

Quote:Here's a bit of it's history

 
[Image: MICROGROUPexten.JPG]

 

You won't catch me buying such old glass for a modern camera. Of course, the next comment is only a question of time. "Fabulous lens, I recall me getting great shots out of it" - blah. Back in those film days were better lenses than that one, especially for macro. And those were double or more more expensive.
That you would not buy "such old glass for a modern camera" is your own loss. This little Nikkor still performs very nicely on modern cameras, I acquired a pristine early Ai-S one a while ago but gave it to a friend who would get more use out of it, because I also have the micro-Nikkor Auto 55mm f3.5. Which works very nicely on my 6D still. And 55mm f1.2.

 

Quote:Do you want to counter tests like that one (with MTF Wink )? Are you sure you got a good copy? One thing I learnt from Roger Cicala's MTF experiments: Never trust a single copy. Especially not in museum lenses, I'd like to add.

 

Btw, the only "spec" I read in your post is the focal length. Being only 0.119 mm off their spec is an excellent value. Or do I miss the other specs?
#4
Quote:Not sure if anyone can dig up MTF info for the 55/2.8 micro AI-S but I have tested one today.

 
I guess you want to see the original Nikon MTF chart for the lens? I have not been able to find it.

https://photographylife.com/lenses/nikon...-f2-8-ai-s

http://slrgear.com/reviews/showproduct.php/product/1403
#5
Quote: 

testing historic lenses?
Not really, I was trained on the MTF bench yesterday and that was a lens we had lying around that is has been essentially locked in a metal block for life so it may easily be coupled to the MTF bench. 

 

http://i.imgur.com/ni1Sm4B.jpg

 

this is no standard F mount =)

 

(as far as evaluating their specs goes - I meant MTF claims.  The 55mm AF-D version may be the same optics - nikon didn't update several lenses when they went AF-D)

#6
Quote:Not really, I was trained on the MTF bench yesterday and that was a lens we had lying around that is has been essentially locked in a metal block for life so it may easily be coupled to the MTF bench. 

 

http://i.imgur.com/ni1Sm4B.jpg

 

this is no standard F mount =)

 

(as far as evaluating their specs goes - I meant MTF claims.  The 55mm AF-D version may be the same optics - nikon didn't update several lenses when they went AF-D)
The AF 55mm f2.8 indeed has the same optical formula as the 55mm f2.8 Ai/Ai-S. The main difference is in the duo-cam barrel design, allowing the AF version to go upto 1:1, where the MF versions only reached 1:2 (and 1:1 with the PK-3 extension tube).
#7
Tested the canon 35 F2 IS USM today.  EFL is 34.412mm, MTF is lower than expected but there was tilt in the test setup.  MTF is at least as good as 90% @ 10lp/mm and 50% @ 30lp/mm in the center at full aperture.

 

http://i.imgur.com/BK2uvbd.jpg

 

http://i.imgur.com/unzdZFK.jpg

#8
Quote: 

http://i.imgur.com/BK2uvbd.jpg

 

http://i.imgur.com/unzdZFK.jpg
Which lens was used for these two photos?
#9
70-300L on my 6D @ 1/60th, F4, ISO 1000

 

Tested a client's lens today - MTF of 78% at 100lp/mm - puts full-frame lenses to shame - I don't think even the otus line has MTF that high.  One of 9 prototypes for the design.

#10
Quote:70-300L on my 6D @ 1/60th, F4, ISO 1000

 

Tested a client's lens today - MTF of 78% at 100lp/mm - puts full-frame lenses to shame - I don't think even the otus line has MTF that high.  One of 9 prototypes for the design.
 

Very clean image from it.  Low CA.
  


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