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Forum: Pentax SLR Lens Discussion
01-09-2023, 11:07 PM
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Forum: Pentax SLR Lens Discussion
01-06-2023, 09:47 PM
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Forum: Pentax SLR Lens Discussion
09-01-2022, 02:04 AM
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Forum: Pentax SLR Lens Discussion
08-18-2022, 11:19 PM
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Supertelemacro bokeh!
Super Cosina 100-500mm in its macro range.
 Berries by Jody Roberts, on Flickr
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Forum: Pentax SLR Lens Discussion
06-07-2022, 03:45 PM
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Forum: Pentax SLR Lens Discussion
06-02-2022, 05:48 PM
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Forum: Pentax SLR Lens Discussion
05-30-2022, 11:40 PM
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Some portrait bokeh. Played a bit with a new-to-me lens (stupid cheap one, to) and was pleasantly surprised. I did overwork the post a bit, but I like the effect at the end so thats all that counts.
Sigma II macro 35-80mm in macro mode (so 80mm), wide open at f/5.6.
 Andrew by Jody Roberts, on Flickr
---------- Post added 05-31-22 at 02:44 AM ----------
And his brother, same lens and settings...
 Patrick by Jody Roberts, on Flickr[COLOR="Silver"]
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Forum: Pentax SLR Lens Discussion
05-22-2022, 10:51 AM
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Picked up a cheap-o Sigma macro zoom from the tail end of the film days for the cost of lunch money, and discovered its surprisingly decent.
Sigma II 28-80, f/8, ISO 200 in macro mode. Haven't had a chance to play with it enough wide open to get an opinion there, but this isn't bad for being stopped down.
Its razor sharp dead center, to.
 Dandelion by Jody Roberts, on Flickr
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Forum: Pentax SLR Lens Discussion
09-07-2021, 07:40 PM
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Water bokeh... or duck bokeh... your choice for a name!
 Duck by Jody Roberts, on Flickr
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Forum: Pentax SLR Lens Discussion
09-06-2021, 02:10 PM
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Forum: Pentax SLR Lens Discussion
08-31-2021, 05:40 PM
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When you have a 500mm lens with a faux-macro range...
Super Cosina 100-500mm f/5.6-8 MC Macro
 Berries by Jody Roberts, on Flickr
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Forum: Pentax SLR Lens Discussion
10-15-2017, 09:49 AM
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85mm Samyang bokeh...
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Forum: Pentax SLR Lens Discussion
09-21-2017, 10:59 AM
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Forum: Pentax SLR Lens Discussion
08-17-2017, 09:58 AM
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Snakey bokeh... (Pentax F 35-70mm)
Ducky bokeh... (Samyang 85mm)
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Forum: Pentax SLR Lens Discussion
04-02-2016, 10:08 AM
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Samyang 35mm f/1.4 @ f/2.2
Probably the best bokeh lens in my bag, with the possible exception of its brother the 85mm. The 35 is far more versatile though.
 Thurston Park; China, Maine by Jody Roberts, on Flickr
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Forum: Pentax SLR Lens Discussion
03-30-2016, 05:12 AM
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Considering how horribly backlit this shot was, the Sammy 85mm continues to impress, flaws be damned.
 Chimping his Shot by Jody Roberts, on Flickr
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Forum: Pentax SLR Lens Discussion
02-24-2016, 05:23 AM
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Forum: Pentax SLR Lens Discussion
02-03-2016, 10:02 AM
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Forum: Pentax SLR Lens Discussion
05-15-2015, 05:13 PM
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Forum: Pentax SLR Lens Discussion
05-15-2015, 03:42 PM
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Forum: Pentax SLR Lens Discussion
04-21-2015, 05:39 PM
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A 135mm lens is a 135mm lens is a 135mm lens. It is designed to project a set value of magnification on a subject, regardless of how its built. If it projects a wider or lesser amount of magnification it is no longer a 135mm lens.
This is why you can have a 35mm ltd which is tiny and weighs next to nothing, or a Samyang 35mm which is built like a tank and probably weighs almost as much. Just because both are made differently, they're still both 35mm lenses because they both project a certain specific amount of magnification upon a sensor/bit of film/whatever. If they magnified more, they would be a longer focal length. If they magnified less, they would be a shorter focal length. This is Photography 101 stuff. The depth of field and all that stuff carries over due to that 35mm length and will not vary. It won't vary because if the lens is built exactly to specs and is exactly 35mm (or 135mm, or whatever) the depth of field can then be predicted as a result because of the math involved.
Of course this isn't the case, because lenses vary in focal length depending on design. That Pentax 50mm may actually be a 49mm. The Canon may be a 51.5mm. The Nikon could be a 49.5mm. All three will be stamped as a 50mm of course because thats what they (mostly) are to the casual photographer.
That's partly where the variance comes into play. The other comes when they measure the aperture values. Pentax's lens could actually be f/1.65, Canon's f/1.75, and Nikon's f/1.775. All three will stamp them as f/1.7 - again - for the ease of labeling and the fact that the difference isn't enough to quibble about.
The basic math involved isn't going to change. If you could increase or decrease depth of field by fiddling with the optics in a lens, it would have been done ages ago and would have been advertised as such. Of course this never happened because when you start fiddling with the optics you are either going to change the focal length or the aperture qualities of the lens or both.
Depth of field dependence on focal length is a constant. Its the fact that lenses may be slightly longer or shorter and have differently measured aperture values compared to whats stamped on them that changes things up and muddies the figures.
This is also why the depth of field is going to stay the same no matter what lens you're using.
A 28mm at f/4 will have the same DoF as a 50mm at f/4 as a 135mm at f/4 as a 300mm at f/4 (provided of course the lenses are actually the focal length advertised and the aperture values are measured to spec). The only difference is going to be how close or far from the subject you need to be to have it the same size in-frame for the camera.
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Forum: Pentax SLR Lens Discussion
04-21-2015, 03:50 PM
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Dude... the laws of physics don't change because someone designed a lens differently. If the DoF is different (and it won't be by much) it's because someone labeled the lens at a different focal length than what it actually is.
Usually when you see the difference is because one brand's f/1.7 is actually a 1.75 while the next's 1.7 is actually 1.8 while the next is 1.65, etc etc
EDIT: Oh yea, bokeh photos...
Auto Sears 28mm, f/2.8 wide open...
 Golden Hour Spike by Jody Roberts, on Flickr
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Forum: Pentax SLR Lens Discussion
04-19-2015, 06:40 PM
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Except thats not bokeh.
Bokeh is simply the aesthetic quality of the blur in the background of the image.
Full stop, don't add on extra baggage to the definition.
Studio portraits usually have extremely pleasing bokeh and zero points of lights to distract the viewer.
EDIT: May as well include a shot - Bower 35mm f/1.4, wide open...
 April 19, 2015 - Bursting Forth by Jody Roberts, on Flickr
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Forum: Pentax SLR Lens Discussion
04-13-2015, 11:53 AM
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Forum: Pentax SLR Lens Discussion
04-05-2015, 07:42 PM
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