I just found this little Vivitar in a second-hand shop, picked it up, and immediately thought to compare it to my Sigma 28/1.8 which I use all the time. According to
the bestiary, this is a Komine-made model. So yeah, let's see what we've got:
The contestants: Vivitar 28mm 1:2.0 MC Close Focus Wide Angle
8 elements in 7 groups
Minimum focusing distance: 23 cm
Maximum magnification: 1:5
Aperture: 6 blades, f/2-f/16
Filter size: 49 mm
Weight: 280 g
Sigma 28mm 1:1.8 EX DG
10 elements in 9 groups
Minimum focusing distance: 20 cm
Maximum magnification: 1:2.9
Aperture: 9 blades, f/1.8-f/22
Filter size: 77 mm
Weight: 500 g
Now, obviously, the Sigma is a modern lens with "A" mode on the aperture ring as well as autofocus, and is therefore quite a bit more convenient to use on a modern camera. It also focuses closer. However, it is a lot bigger and heavier than the Vivitar! Not only that, but seeing as there are few (inexpensive) options for fast lenses in the 28 mm range, and given how useful this focal range is as a walk-around lens on an APS-C DSLR -- especially when the lens does close-focus -- the Vivitar could be potentially interesting for many Pentax DSLR owners.
All these pictures were shot on a K-5 on a tripod, manually focused in zoomed-in LV mode. RAW processed in Lightroom, default settings. No attempt made to correct exposure. The shutter speed was the same for a given aperture with both lenses.
Brick wall series (sharpness test):
Sigma:
f/1.8 f/2 f/2.8 f/4 f/5.6 f/8 f/11
Vivitar:
f/2 f/2.8 f/4 f/5.6 f/8 f/11
As uninteresting as brick walls are, here they allow us to note a couple of things right away:
- While both lenses are nominally 28mm, the Sigma has a slightly wider field of view.
- The Vivitar seems to let in slightly more light at the same shutter speed and aperture, i.e. exposes brighter.
- The Sigma has slightly more contrast and seems to render colours a bit warmer, but beware that the differing exposures exaggerates this effect. Equalize the exposures and they're much closer.
- The Vivitar is visibly sharper in the corners, right up to about f/8. In the center, I find they're pretty much equal.
Close-focus/bokeh test:
In this test, I focused the Vivitar to its absolute closest point and then adjusted the Sigma to match. The focus point looks to be a bit further back on the Sigma. Sorry about that. Remember that the Sigma CAN focus quite a bit closer than this, but I wanted to level the playing field.
Vivitar:
f/2 f/2.8 f/5.6
Sigma:
f/2 f/2.8 f/5.6 - Again, we can see that the Vivitar lets in a little bit more light and has a different field of view -- the camera was not moved between the lens change.
- The bokeh on the Vivitar is a little busy (check out the "KR-10" writing in the f/2 sample) owing to the mere 6 aperture blades. The Sigma is smoother with its 9 blades.
- I much prefer the calmer rendering of the Sigma in the f/2 image. Already by f/2.8, I don't really have a clear preference.
- Both lenses display a little CA/PF. It is not really a big deal and gone by f/5.6.
So, a conclusion from this very unscientific test? Well, draw your own, if you want. The Sigma has better bokeh and focuses quite a bit closer, but the Vivitar is actually slightly sharper overall. If I had to sell one of these I would keep the Sigma, but the Vivitar seems to be a great lens for its size and price. I got it for $65 with a Ricoh KR-10, a Rikenon 50/2, Soligor C/D 80-200, bag and flash.
EDIT: Oh yeah. The Sigma had a Hoya UV filter on, the Vivitar nothing. So keep that in mind. It didn't even occur to me until right now.
Last edited by Erik; 08-01-2012 at 09:03 AM.