Ok lets start off with the kit 14-45 zoom at about 24mm at f4.8 (wide open)
now, lets look at the Pentax 110 24mm lens ... there is no aperture, so its at f2.8
you don't even need to be pixel peeping to see that its reasonably soft around the edges. Just take a look at the green fabric in the middle foreground
At this overview size there isn't much obvious advantage in DoF between f2.8 and 4.8 ... in fact its really only just over a stop.
So lets have a quick pixel peep at the middle of the image where I focused on (manually) with each of the lenses. These images are about 50% scaled on this page, but if you click the image you'll get a 100% screen grab of the image.
The Kit zoom at 24mm
and then the 110 24mm lens
now lets look at the middle edge of the frame ... the Kit zoom
and the 110 24mm
hmmm ... not my thing, but maybe yours
summary:
for me I just don't see any significant advantage in the DoF found in the Pentax 110 lens over the kit zoom. These images really should show this more as the target is quite close to the camera, when compared to shallow normal depth of field on full fame 35mm images the difference here is not so much.
The 110 lenses are certainly nice and compact, almost absurdly so on the G1 / GH1 cameras ..
Perhaps on the GF it may be a more sensible alternative. However for me at least the Olympus 17mm or the Panasonic 20mm (despite it being more expensive) would be a better choice for a fixed focal length lens.
Why? well you get
- AF
- immediate zoom to confirm focus by just turning the lens (you need to press a few buttons)
- something other than "wide open" (you know, you can stop down to 5.6 and really sharpen up)
I'm sure it makes even more sence on the GF. So for travllling light you can stick the 50mm lens in your pocket easily and when you pack that with either a normal (like the Oly 17mm or the Panasonic 20mm) you get a great compact two lens outfit.
The 18mm or the 24mm Pentax 110 ... well in my view you its sota fun to play with (and you'll need the adaptor for the 50mm, but you can leave home without it.
If you can get through the Japanese, I recommend reading this site. It was written before there were even commercial adaptors for mounting the 11o lenses on the G1
:-)
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2 comments:
You are really comparing DoF in the Corners and not lens sharpness since the zoom and Pentax are at different apertures. Not saying the Pentax are great lenses, but the 24mm is pretty decent. If you add a paper aperture behind the lens to achieve ~f5.6, the len inproves... the advatage at this point is really size more than performance though. Thanks for posting your results!
Mark
if you examine the image and consider the angles I'm sure you'll find that the place I chose in the outer area of the image is actually quite close to the exact plane of focus.
As you can see the camera is higher and angled down. So if you draw a line from the camera to the sewing machine and then take a perpendicular from that it intersects with that sewing kit.
Considering that aspect further and applying refocus to the lens, no amount of refocus made that any clearer (quite obvious when using the focus aid zoom tool on the G1)
At the end of the day, using the aperture you suggested (and of course there are many home brew methods out there on the www) may improve it a bit, but then as you seem to acknowledge the advantage of the 24mm is about compact rather than performance.
Stopping down may improve the quality of the edges but removes the shallow depth of field and shutter speed advantages. So what you gain in clarity stopping down (which still does not equal the 24mm from what I've seen on other sites) you loose in shallow DoF.
Its just for me the balance of that equation results in something I don't want. NB my Nokia phone gives better image quality than the G1 with the 24mm
YMMV
:-)
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