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Four 50s compared.
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PostPosted: Sat May 15, 2010 11:37 pm    Post subject: Reply with quote
Arkku wrote:

There can be focus shift when stopping down.


I have not heard of this, can you enplane further?


PostPosted: Sun May 16, 2010 12:09 am    Post subject: Reply with quote
If you want to see more tests on "standard" F1.4 lenses, look into this thread:
"Super Takumar F1.4 or Rokkor 58mm F 1.4?"
http://forum.mflenses.com/super-takumar-50mm-f1-4-or-rokkor-58mm-1-4-t28217.html


It's not a bokeh test, but test charts done by myself the last couple of days.
The lenses are:

MC Rokkor 58mm F1.4
MC Rokkor 50mm F1.4
Super-Takumar 50mm F1.4
SMC Takumar 50mm F1.4
MD Rokkor 50mm F1.4
Olympus OM 50mm F1.4
Nikkor 50mm F1.4
Canon SSC 50mm F1.4
Konica Hexanon 57mm F1.4


PostPosted: Sun May 16, 2010 12:11 am    Post subject: Reply with quote
revers wrote:
Arkku wrote:

There can be focus shift when stopping down.


I have not heard of this, can you enplane further?


It's caused by spherical aberration. If the aberration is perfectly corrected, rays of light coming from all heights of the lens pupil will have the same focal point. However, if spherical aberration is either under- or overcorrected, the rays from the edges of the pupil intersect at a different point than those from the centre. When the lens is stopped down, the edges of the pupil are cut off by the smaller aperture and this results in focus shift.

This is common with fast lenses in particular, which is why e.g. f/1.2 lenses are often better focused at f/2 or f/2.8 if one means to stop down, even though common sense would dictate that f/1.2 gives the most precise focusing due to ultra-shallow depth of field. (Spherical aberration can also cause lower contrast at large apertures due to a slightly unfocused “halo” showing around the focused area. This, and smoother background bokeh from undercorrected spherical aberration actually makes many such lenses well-suited for portraits.)

Last edited by Arkku on Sun May 16, 2010 12:27 am; edited 1 time in total


PostPosted: Sun May 16, 2010 12:18 am    Post subject: Reply with quote
dnas wrote:
If you want to see more tests on "standard" F1.4 lenses, look into this thread:



Thanks, I did view this thread previously. Nice work!


PostPosted: Sun May 16, 2010 12:25 am    Post subject: Reply with quote
Thanks Arkku.

I did notice that with at least one lens (maybe the TaK) that the focus was good stopped down but when I opened up to fine tune it was off quite a bit. This information is very helpful.


PostPosted: Sun May 16, 2010 12:56 am    Post subject: Reply with quote
So that lens was after Rokkor and before AF? I don't know why they dropped the Rokkor name.


PostPosted: Sun May 16, 2010 1:21 am    Post subject: Reply with quote
woodrim wrote:
So that lens was after Rokkor and before AF? I don't know why they dropped the Rokkor name.


This lens is approx. an 1982 or 83 lens. It's a MD Gen. 3 lens.
The Gen. 2 lens would have the Rokkor name on it.

This is the lens I would choose. Smaller ,lighter weight , better coatings.


PostPosted: Sun May 16, 2010 1:26 am    Post subject: Reply with quote
woodrim wrote:
So that lens was after Rokkor and before AF? I don't know why they dropped the Rokkor name.


The earlier Minolta MD lenses still had the "Rokkor" on them, from 1977 until about 1981.

The Minolta MD lenses from around 1981 no longer had the "Rokkor", so that lens has to be post 1981. These MD lenses appeared around the same time as the Minolta X-700 (which was produced until 1999!!!!) I think the later MD lenses were made up to about then.

Minolta produced the newer Minolta AF mount(later to become the Sony Alpha mount) in 1985, but even so, they continued to produce the X-700.


PostPosted: Sun May 16, 2010 2:47 am    Post subject: Reply with quote
My MC Rokkor is from 1974.


PostPosted: Sun May 16, 2010 3:42 am    Post subject: Reply with quote
woodrim wrote:
My MC Rokkor is from 1974.


The first MC Rokkors came on the scene around 1966. They improved coatings and some designs for more than 10 years.


PostPosted: Sun May 16, 2010 3:59 pm    Post subject: Reply with quote
Arkku wrote:
revers wrote:

I assure you they were all very accurately focused on the exact same spot using the expanded view with the lens wide open & then stopped down.


There can be focus shift when stopping down.


+1


PostPosted: Sun May 16, 2010 4:08 pm    Post subject: Reply with quote
woodrim wrote:
So that lens was after Rokkor and before AF? I don't know why they dropped the Rokkor name.


Apart from the reasons of market, the optical design is very different. The production of the series MD, it is more economic than the series rokkor. Wink


PostPosted: Sun May 16, 2010 11:35 pm    Post subject: Reply with quote
francotirador wrote:
woodrim wrote:
So that lens was after Rokkor and before AF? I don't know why they dropped the Rokkor name.


Apart from the reasons of market, the optical design is very different. The production of the series MD, it is more economic than the series rokkor. Wink


Yes, the designs are cheaper.

I've worked on quite a few MC and MD lenses. Mostly this has involved removal of fungus, which is often reasonably successful if you can get to the affected lens element(s). The lens elements and their coatings seem to be fairly resistant to damage from fungus.

The MC lenses were built in a fairly traditional, with all metal rings holding lens elements in place. The earlier MD were similar in that repect. This woud usually have involved assembly of each individual lens element by hand.

However, the later MD lenses have complete groups which are molded together with reinforced plastic. If you get any fungus between these groups, then you usually cannot remove it. In a lot of cases, these molded lens groups have only two groups to assemble into the finished lens, so this is one reason why they were cheaper. There is also a lot more plastic in the construction.


PostPosted: Mon May 17, 2010 12:02 am    Post subject: Reply with quote
The minolta 50/1.4 is by far my favorite here !
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