Rokkor 55mm lenses compared

caspert79 · Joined: 31 Oct 2010 Posts: 3152 Location: The Netherlands

A near infinity test and bokeh test. I threw in the Petri 55/1.8 as well to make it more interesting.

First, the center crops:

CenterComparison by devoscasper, on Flickr
Wide open, the Auto Rokkor PF 55mm f/2 seems best, but it's also the slowest lens. The Auto Rokkor-PF 55mm f/1.8 is a close second. The Rokkor 55/1.7 is a bit softer than the other Rokkors, but the Petri is softest wide open. Closed down, starting @ f/2.8, the Petri shows the crispest results IMO, closely followed by the Auto Rokkor-PF 55/1.8. At smaller apertures, the color balance of the 55/2 seems to change a bit. No idea why this happens.

Then the corner crops:

CornerComparison by devoscasper, on Flickr

I've concluded it before: the Petri is an excellent landscape lens, with very usable corners @ f/2.8, and perfectly sharp corners @ f/4. The Rokkor 55/1.8, being the oldest lens, needs most stopping down for sharp corners, and it doesn't quite reach the sharpness of the other lenses. Clearly, this is a weakness of the lens that was addressed by Minolta with the introduction of it's successor, the 55/1.7, but at the cost of somewhat lesser crisp center results it seems.

Then, bokeh. I've noticed before, that the 3 Rokkors allow for very nice, buttery soft bokeh. Let's see how they compare:

bokehcomparison by devoscasper, on Flickr

The Rokkor lenses are capable of producing nice soft bokeh balls, that are very uniform in nature (no rings). Wide open, I would say the Rokkor 55/1.7 wins by a hair. The Petri's bokeh is nice as well, but it's bokeh balls are less uniform, and thus a bit more distracting. Stopped down a bit, the Rokkor 55/1.8 has this nicest bokeh balls IMO, because of it's rounder aperture. Then, there's is a difference between the lenses in their MFD. Some lenses are able to focus a bit closer than others. This expands the creative ability a bit, allowing for more blown out backgrounds. Here a shot of all lenses, wide open, at their MFD:

Minfocuscomparison by devoscasper, on Flickr

The Rokkor 55/1.8 allows for the closest MFD. There's no MFD reading at this setting, but it's closer than 50cm, probably around 47cm. By the way, I'm using the oldest version of the Rokkor, from the late 50's, with 55mm filter thread diameter. Because of this, the Rokkor 55/1.8 allows for the softest bokeh.

Dejan · Joined: 05 Jan 2021 Posts: 148 Location: Belgrade, Serbia

The biggest difference, when it comes to Minolta 55mm F1.7, is obvious with mid range and long distance bokeh. That's where it shines, at least if softer bokeh is desirable.

stevemark · Joined: 29 Apr 2011 Posts: 3953 Location: Switzerland

Interesting to see how much things improved when going from the AR 1.8/55 to the MC 1.7/55 (MC-I or MC-II?). I wasn't aware of that since usually don't test normal lenses ...

That mirrors the reported improvement when going from the AR/MC-I 1.4/58mm to the MC-II 1.4/58mm, reported by MP (or PP?) as well as Dieter Gabler in his books about the SR-T.

S

caspert79 · Joined: 31 Oct 2010 Posts: 3152 Location: The Netherlands

stevemark · Joined: 29 Apr 2011 Posts: 3953 Location: Switzerland

caspert79 · Joined: 31 Oct 2010 Posts: 3152 Location: The Netherlands

Sakyaputta · Joined: 01 Feb 2022 Posts: 59 Location: Beijing, China

caspert79 · Joined: 31 Oct 2010 Posts: 3152 Location: The Netherlands

Sakyaputta · Joined: 01 Feb 2022 Posts: 59 Location: Beijing, China

caspert79 · Joined: 31 Oct 2010 Posts: 3152 Location: The Netherlands

Thanks for your info. Mine starts with sn 243â€¦ and should therefore be the (7/7) version. Remember anything about corner performance of this particular version?

Sakyaputta · Joined: 01 Feb 2022 Posts: 59 Location: Beijing, China