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Forum: Pentax SLR Lens Discussion 10-26-2016, 08:22 AM  
55mm/f1.2 Porst versus Revuenon writeup
Posted By newmikey
Replies: 16
Views: 3,495
That's what I do as well.

I also run a short script after downloading which puts f1.2 into the exif but like you, I cannot verify after the fact if actually shot at that aperture. I need some aperture info in the exif as otherwise my HDR software won't play ball and segfaults.
Forum: Pentax SLR Lens Discussion 10-26-2016, 04:14 AM  
55mm/f1.2 Porst versus Revuenon writeup
Posted By newmikey
Replies: 16
Views: 3,495
That's very encouraging! I had thought of selling off the Porst but I might reconsider now...

It may be "twisted" but it makes interesting reading nevertheless. The better contrast versus dreamier images issue I had noticed when comparing both lenses side by side. Good to see that observation confirmed!

Thanks for all of that info, much appreciated!
Forum: Pentax SLR Lens Discussion 10-24-2016, 02:33 PM  
55mm/f1.2 Porst versus Revuenon writeup
Posted By newmikey
Replies: 16
Views: 3,495
There's a lot of confusion but I think your M42 Tomioka is a step up from the later K-bayonet Porst and Revuenon incarnations which seem to have been made by Cosina as far as I have researched. You truly have a gem in your hands there but honesty requires that I clearly state that neither one of my lenses is said to perform as good as the Tomioka-made 55mm's in M42 version.
Forum: Pentax SLR Lens Discussion 10-06-2016, 08:02 AM  
55mm/f1.2 Porst versus Revuenon writeup
Posted By newmikey
Replies: 16
Views: 3,495
I had a unique chance to obtain both the Porst as well as the Revuenon 55mm/f1.2 lenses via eBay. In the short time I have used both I can already provide the below impressions.

The Porst is a solidly built lens, all metal with a black anodized lensmount (more on that below). The Reveunon is also all-metal but has a blank-metal mount. Both have unusually large rear elements obviously requiredbecause of the large maximum aperture of f1.2

On both lenses, the front element is quite large as well but the Porst one is slightly more recessed than the Revuenon. Nevertheless it seems the Porst is slightly more susceptibe to contrast reduction on account of stray light hitting the front element and I have immediately supplemented the Porst with a metal lenshood which visibly improves the contrast. I have also ordered a similar hood (58mm thread instead of the 55mm for the Porst) for the Revuenon but that is more to protect the front element from harm as its contrast is already quite decent even at full opening.

Available exposure modes:
Of course both are manual lenses without AF connector or electronic contacts. At max aperture both function as expected in M as well as Av mode.
As the Porst lensmount is non-conductive and does not short out two contact on the lensbody, the green button does not work but a small piece of conductive material stuck between lens and mount solves that (I use a piece of the inner wrapping of a pack of cigarettes). I intend to use a bit of self-adhesive copper tape on the mount as a more permanent solution. Another option would be to open up the mount and remove a little spring but I'm sure that is a bit too drastic for me. The reason to purchase the lens it to use it wide open, otherwise one could equally use any of the AF 1.4 or 1.8 options Pentax offers. (I have the DA50mm/f1.8 - great little gem)

The Revuenon has a conductive mount so can be used with the green button exposure without any modding, the aperture closes and the exposure meter sets a correct shutterspeed.

Image quality:
This where I got somewhat of a surprise. I would have expected both lenses to perform quite similarly but nothing is further from the truth! The Porst delivers a dreamy, almost etheric image at full aperture with halo-like transitions and smooth bokeh. The colours are quite lively and contrast (with a hood) is decent. At smaller aperures the dreamy look disappears and the image gains loads of sharpness and detail. The Revuenon has none of that dreamy-like quality and seems to have a somewhat cooler rendition of colors. Even wide-open at f1.2, the sharp parts of the image are very sharp and with a few stops in, that sharpnes spreads corner to corner. Here too, bokeh is excellent with smooth transitions between sharp and unsharp a creamy OOF circles.

The two lenses are quite distinctively different, except for the build quality which is excellent in both. Both focusrings turn smoothly and easily, the Porst seems to have a longer throw. For now, I'll be using both with pleasure, one for the dreamy look and the other for the wonderful rendering and sharpness. Evenetually, I'll probably get rid of one as I already have quite a bit of glass and do not need to be caught in indefinite indecision. "There can be only one!".
I can offer two non-scientific examples shot on different days under slightly different lighting conditions. Are you up for a challenge? Which image belongs to which lens?

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