Bosun Higgs
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This post was prompted by my purchase of a Sankyo Kohki 105mm f2 lens, I already had the 100mm f1.8, but the 105mm was for sale at such an attractive price, I just could not resist ;O)
When I first looked at Sankyo 100mm(ish) lenses I was torn between the 100mm and the 105mm, and could not decide, but in the end the decision was made for me when a defective 100mm lens came up at a very low price. As I knew I could repair the lens, it was a no-brainer.
Strangely, these two nearly identical lenses were produced side by side for quite a while. The 100mm f1.8 was part of SK's "standard" lens range, but the 105mm f2 was part of their "High Speed" lens range, which is odd as it is slower than the 100mm.
Both lenses were made in fixed mount, and later, with interchangeable mounts; Unidapters for the standard lenses such as the 100mm, and special "High Speed" adaptors for lenses like the 105mm. With my lenses the 100mm is a Unidapter (Nikon F in this case), and the 105mm has a fixed Canon FD mount.
Precise dating on these lenses is difficult, but these two are definitely 1960's vintage. The earliest mention of the 105mm known at present is a 1965 EPOI advert for all four of the High Speed Lenses.
Having both lenses, I thought that instead of just describing the new 105mm, I would also do a comparison with the 100mm, and my usual yardstick, the Canon FD 100mm f2.
The Tests.
The test shots were taken with each lens at maximum aperture using the same A7rII body with the same settings. Images were put through ACR with default settings, no correction of vignetting or fringing.
My main interest in lenses this old is the bokeh and rendering, so I took no stopped down shots.
The Lenses.
From L to R, SK 100mm f1.8, SK 105mm f2, Canon FD 100mm f2. All mounted up as used for the tests.
The Sankyos were probably made mid 1960's and the Canon was introduced in 1980, this particular lens was made in 1986. The Sankyos were definitely designed by traditional means, but there is a slight chance that the Canon could have benefited from early computer optimisation. Canon is unclear which nFD lens designs had CAD help, apart from the aspherics.
Optical diagrams of the three lenses to the same scale,
All three lenses are Ernostar derived designs, the similarities are obvious. This is one of my favourite lens designs and is capable of excellent bokeh results. The two SKs are 5:4 designs and the Canon is a 6:4.
As mentioned above, the 105mm SK is a fixed mount lens (ironically Canon FD in this case), and the 100mm is a Unidapter lens (Nikon F).
The Results.
Contrast levels look very similar in these untweaked images.
Note the stronger edge emphasis in the 100mm SK's bokeh bubbles.
Although the 100mm has more blur, the less textured background from the 105mm can sometimes look smoother.
Background bokeh differences are very apparent here. The texturing inserted in the 100mm bokeh is offsetting its greater blur.
Note the strong catseyeing in the Canon pane, the 100mm SK shows the least of all.
The two SK lenses are about even in sharpness, with wide open shooting and the DOF implications of this, it was difficult to tell them apart. The Canon was much sharper, every time, which does make me wonder about the possibility of CAD playing a part there.
Contrast-wise there was little to choose between the three, which is pretty impressive considering the Canon has the benefit of multicoating. The 105mm backgrounds sometimes looked a little less contrasty, but I think that this was probably due the softer bokeh effects (more on this later).
Vignetting was slight on all three lenses and field curvature was not a problem.
The 105mm showed the most fringing, with some subjects this could almost resemble a slight "glow", the 100mm had much less, and in comparison, the Canon seemed to have none.
The Bokeh.
Bokeh bubbles were predictably largest from the 100mm with its aperture advantage. Once again, the Canon had the smallest bubbles, noticeably smaller than the 105mm despite them both being f2 lenses.
Bokeh bubbles cropped from one of the shots above, the size difference is obvious. Despitethe 105mm and Canon both being f2 lenses, the Canon bubbles are mcuh smaller.
The bokeh bubbles from the 100mm were more strongly outlined than those from the 105mm, consequently they tended to stack, whereas the 105mm bubbles tended to blend. This was especially true with small specular light sources.
The bubble differences are reflected in the general bokeh of the lenses. Although the 105mm has smaller bubbles, the soft edges increase the blur effect, and for more diffuse lit areas the two lenses produce similar blur. In fact the edged bubbles of the 100mm can inject quite a bit of texture into the bokeh, and with some subjects, it can seem that it was producing less background blur than the slower 105mm because of this.
The Canon produced less background blur than either of the SKs. It also has quite strongly edged bokeh bubbles, and these inject far more texture into the bokeh than either of the SKs.
The Canon had the most catseyeing, and of the two SKs, the 100mm had the least. I saw no swirl, at any time, from any of these lenses.
The Bottom line.
The two SKs acquitted themselves very well against the Canon which is a 20 year later design and has multicoating. The main deficit was in sharpness, the Canon was clearly superior.
The sharpness difference is relative. These are all old lenses (the SKs are 60 years old!) and a modern computer optimised, 12-plus element, Sigma ART or Zeiss lens, packed with exotic glass types, will make just about any lens from this era look severely lacking.
Bokeh-wise the SKs produce more blur, the 100mm backgrounds show the least detail, but the 105mm can sometimes seem smoother. Background details were much more noticeable in the Canon's output and its rendering was much more textured.
As always, bokeh is largely down to personal taste, if you like smooth, then the SKs will probably suit you best. All of these lenses produce more pleasing bokeh to my eyes than the aforementioned modern glass, which is often described as having "clinical" rendering.
I have not had the two SKs long enough to get a good feel for their output, so I am not going to express a preference for either. If you have been thinking about getting one of these lenses for bokeh purposes, then I hope this small comparison will be of some aid to you in your choice.
Finally, I think that it has been a little unfair on the SK 105mm to have its coverage diluted in a group test, so I will leave you with a few stereos taken with that lens alone.
It can do this:-
When I first looked at Sankyo 100mm(ish) lenses I was torn between the 100mm and the 105mm, and could not decide, but in the end the decision was made for me when a defective 100mm lens came up at a very low price. As I knew I could repair the lens, it was a no-brainer.
Strangely, these two nearly identical lenses were produced side by side for quite a while. The 100mm f1.8 was part of SK's "standard" lens range, but the 105mm f2 was part of their "High Speed" lens range, which is odd as it is slower than the 100mm.
Both lenses were made in fixed mount, and later, with interchangeable mounts; Unidapters for the standard lenses such as the 100mm, and special "High Speed" adaptors for lenses like the 105mm. With my lenses the 100mm is a Unidapter (Nikon F in this case), and the 105mm has a fixed Canon FD mount.
Precise dating on these lenses is difficult, but these two are definitely 1960's vintage. The earliest mention of the 105mm known at present is a 1965 EPOI advert for all four of the High Speed Lenses.
Having both lenses, I thought that instead of just describing the new 105mm, I would also do a comparison with the 100mm, and my usual yardstick, the Canon FD 100mm f2.
The Tests.
The test shots were taken with each lens at maximum aperture using the same A7rII body with the same settings. Images were put through ACR with default settings, no correction of vignetting or fringing.
My main interest in lenses this old is the bokeh and rendering, so I took no stopped down shots.
The Lenses.
From L to R, SK 100mm f1.8, SK 105mm f2, Canon FD 100mm f2. All mounted up as used for the tests.
The Sankyos were probably made mid 1960's and the Canon was introduced in 1980, this particular lens was made in 1986. The Sankyos were definitely designed by traditional means, but there is a slight chance that the Canon could have benefited from early computer optimisation. Canon is unclear which nFD lens designs had CAD help, apart from the aspherics.
Optical diagrams of the three lenses to the same scale,
All three lenses are Ernostar derived designs, the similarities are obvious. This is one of my favourite lens designs and is capable of excellent bokeh results. The two SKs are 5:4 designs and the Canon is a 6:4.
As mentioned above, the 105mm SK is a fixed mount lens (ironically Canon FD in this case), and the 100mm is a Unidapter lens (Nikon F).
The Results.
Contrast levels look very similar in these untweaked images.
Note the stronger edge emphasis in the 100mm SK's bokeh bubbles.
Although the 100mm has more blur, the less textured background from the 105mm can sometimes look smoother.
Background bokeh differences are very apparent here. The texturing inserted in the 100mm bokeh is offsetting its greater blur.
Note the strong catseyeing in the Canon pane, the 100mm SK shows the least of all.
The two SK lenses are about even in sharpness, with wide open shooting and the DOF implications of this, it was difficult to tell them apart. The Canon was much sharper, every time, which does make me wonder about the possibility of CAD playing a part there.
Contrast-wise there was little to choose between the three, which is pretty impressive considering the Canon has the benefit of multicoating. The 105mm backgrounds sometimes looked a little less contrasty, but I think that this was probably due the softer bokeh effects (more on this later).
Vignetting was slight on all three lenses and field curvature was not a problem.
The 105mm showed the most fringing, with some subjects this could almost resemble a slight "glow", the 100mm had much less, and in comparison, the Canon seemed to have none.
The Bokeh.
Bokeh bubbles were predictably largest from the 100mm with its aperture advantage. Once again, the Canon had the smallest bubbles, noticeably smaller than the 105mm despite them both being f2 lenses.
Bokeh bubbles cropped from one of the shots above, the size difference is obvious. Despitethe 105mm and Canon both being f2 lenses, the Canon bubbles are mcuh smaller.
The bokeh bubbles from the 100mm were more strongly outlined than those from the 105mm, consequently they tended to stack, whereas the 105mm bubbles tended to blend. This was especially true with small specular light sources.
The bubble differences are reflected in the general bokeh of the lenses. Although the 105mm has smaller bubbles, the soft edges increase the blur effect, and for more diffuse lit areas the two lenses produce similar blur. In fact the edged bubbles of the 100mm can inject quite a bit of texture into the bokeh, and with some subjects, it can seem that it was producing less background blur than the slower 105mm because of this.
The Canon produced less background blur than either of the SKs. It also has quite strongly edged bokeh bubbles, and these inject far more texture into the bokeh than either of the SKs.
The Canon had the most catseyeing, and of the two SKs, the 100mm had the least. I saw no swirl, at any time, from any of these lenses.
The Bottom line.
The two SKs acquitted themselves very well against the Canon which is a 20 year later design and has multicoating. The main deficit was in sharpness, the Canon was clearly superior.
The sharpness difference is relative. These are all old lenses (the SKs are 60 years old!) and a modern computer optimised, 12-plus element, Sigma ART or Zeiss lens, packed with exotic glass types, will make just about any lens from this era look severely lacking.
Bokeh-wise the SKs produce more blur, the 100mm backgrounds show the least detail, but the 105mm can sometimes seem smoother. Background details were much more noticeable in the Canon's output and its rendering was much more textured.
As always, bokeh is largely down to personal taste, if you like smooth, then the SKs will probably suit you best. All of these lenses produce more pleasing bokeh to my eyes than the aforementioned modern glass, which is often described as having "clinical" rendering.
I have not had the two SKs long enough to get a good feel for their output, so I am not going to express a preference for either. If you have been thinking about getting one of these lenses for bokeh purposes, then I hope this small comparison will be of some aid to you in your choice.
Finally, I think that it has been a little unfair on the SK 105mm to have its coverage diluted in a group test, so I will leave you with a few stereos taken with that lens alone.
It can do this:-
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