|
Forum: Pentax SLR Lens Discussion
11-17-2008, 11:52 AM
|
| |
While I'm at it, here's a more formal test of the lens (warning: v large):
Compared with the same test shot with a Yashinon DS-M 50mm f1.4, an M42 lens:
As someone points out above, the Porst goes straight from f1.2 to f2.0, with no click stops in between, and has whole stops down to f22.
|
|
Forum: Pentax SLR Lens Discussion
11-17-2008, 11:37 AM
|
| |
Right, I spent Sunday wandering around the V&A, the Natural History Museum, and the Science Museum, with my modified Porst 55mm. The mirror blocking wasn't an issue, because it only happens when the lens is focused beyond infinity, and I will only ever never need to focus beyond infinity at the moment of my death.
I usually took two shots quickly - one at f1.2 and a second one a couple of clicks stopped-down until I felt I couldn't handhold the exposure any more. Looking at the EXIF data, I probably stopped down to f4, but that's not exact. The metering was odd - at f1.2 the images tended to be slightly overexposed, and as I stopped down they became underexposed. Perhaps it's a general characteristic of old lenses with manual adapters.
I've used "auto contrast" but I haven't applied any sharpening. All of the images were taken with a Canon 5D at ISO 1000-1600.
Here's a general shot of Queen Victoria, taken at f1.2:
Here's an example of the vignetting at f1.2 versus stopped down a little:
Here's a demure-looking lady at f2, which is the best aperture to use in my opinion:
Here's a comparison of the relative sharpness at f1.2 and stopped down:
A mean-looking fellow at f2.0:
A creepy girl:
This lady doesn't illustrate anything, she's just nice:
My general impression is that at f1.2 it's really a soft-focus portrait / special effect lens. At f2.0 there's a nice balance of sharpness and blur. It doesn't become normal until f2.8, and beyond that it's no slightly less sharp than my 50mm Yashinon f1.4 at all apertures. For low light situations it's much better to just increase the ISO, but on the other hand the blur at f2.0 is very nice. Also, the vignetting is striking. The lens looks great too, like a gleaming pool of water.
|
|
Forum: Pentax SLR Lens Discussion
11-14-2008, 10:33 AM
|
| |
"I've concluded that the Porst has a character that showed across different users similarly which was to my liking."
Veering off-topic slightly, and largely as a result of this very thread (it's one of the top Google returns for "porst 55mm f1.2"), I went and bought one of these Porsts. Sadly the other lenses mentioned in the thread aren't readily available on Google at the moment, and I spotted a bargain. It's always nice to have an f1.2 lens, it exudes bigness, and this particular lens looks like a giant glass eye.
Anyway, it's a PK-mount lens that I have hacksawed to fit onto a Canon 5D. I chopped off the aperture pin, the pointy-out Pentax pointy-out prong, and also the ring that protrudes beyond the bayonets. It mounts and works a treat. It doesn't seem much brighter than the 50mm Yashinon f1.4 and Takumar f1.4 I also use, but I haven't had a chance to test it fully. I'll probably take the train to London tomorrow and shoot some sculptures at f1.2, which I can post here if you want. It does seem noticeably soft at f1.2, but I don't mind that effect.
One problem though. The lens focuses and works perfectly except at absolute infinity. One fraction of a twist before infinity it is fine; but at absolute infinity it must be catching on the mirror, because there is a typical dark area on the photograph, and the shutter sound is noticeably slow. I assume that my PK adapter (one of those generic "focus confirm" jobs from eBay) is just fractionally too thin. Does anybody know a good place where I can buy a high-quality PK-EOS adapter?
I apologise if the butchery of this lens has upset people. Nonetheless there are plenty of them about, they seem very well-made by modern standards, far superior to all of Canon's mid-range lenses.
|
|
Forum: Pentax SLR Lens Discussion
11-11-2008, 01:19 PM
|
| |
I'm fairly sure I have one of these; I found this thread via Google, because I was curious about the lens, which I have just hacksawed so that it will mount properly on a Canon 5D with a PK-EOS adapter.
My copy has 35-70mm 1:35-4.8 written on the front rather than 3.5-4.6, and I can't find anything about it on the internet either. It has a macro scale, although it's not very macro. I surmise it was a kit lens. I got it free with a Pentax P30, which came with a longer Tokina zoom lens (70-135mm or similar) as a set.
I've mounted it on my Canon 5D, which is probably heresy in this forum, but then again it's a kit zoom from the 1980s. The build quality is nonetheless much better than modern kit zooms - metal and rubber, with a snappy aperture and a smooth zooming motion. It zooms outwards to 35mm, inwards to 70mm. Optically it seems to have nothing wrong with it, but I haven't really tested it yet. The mount is very silver, almost like a mirror.
The reason I bought a PK-EOS adapter is because I am curious about the various odd 55mm f1.2 lenses out there, e.g. the Revuenon and Cosina and Porst 55mm f1.2s, but that's another thread (quite literally so in this case).
|
