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Forum: Pentax Camera and Field Accessories
12-08-2018, 03:12 PM
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With a suitable wedge any tripod head suitable for the weight of lens & having a rotational ability should be workable.
The wedge basically mounts between the tripod & head & holds the head at the right angle for your lattitude. They are often homemade. :)
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Forum: Canon, Nikon, Sony, and Other Camera Brands
02-16-2018, 05:09 AM
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Funny I've been shooting older mirrorless cameras for years & I've never found EVF DR to be a problem at all.
For action shots a DSLR works better than my mirrorless cameras, but they doesn't win in any other categories IMO.
For flexibility the mirrorless cameras are streets ahead.
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Forum: Photographic Technique
02-05-2018, 06:59 AM
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All these configurations will work & all will give different results.
TC+ET+Lens will give the highest magnification (assuming all extension tubes are the same length)
Extension tubes have more effect for shorter focal lengths so switching TC & ET will reduce the magnification but increase working distance.
I personally find stacking lenses to be an easier approach to ultra macro, with the wider lens reversed front to front with the longer one & the longer one mounted normally on the camera. Magnification is the ratio of focal lengths with both lenses focused to infinity, focusing the non-reversed lens closer will marginally increase magnification. (50mm reversed on 200mm gives 4x ) I always leave the reversed lens wide open & focused at infinity, anything else increases the chances of vignetting - which can be pretty bad with some lens combinations.
Have a look at Coupling lenses for extreme macro for a better written explaination, along with details on most of the other options...
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Forum: Pentax SLR Lens Discussion
10-16-2017, 08:10 AM
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Surely the no barrier readings include the beta & gamma sources which on the numbers you give (ignoring the +) constitute half the counts. Likewise the readings with the cap would include gamma. Giving:
100 mR/hr Gamma
150 mR/Hr Beta
250+ mR/Hr Alpha
Using the whole body weighting factor that converts to (moving to SI units)
1mSv Gamma
1.5 mSv Beta
2.5+ mSv Alpha
Even totaled that's well below the 0.1Sv threshold for detectable chromosome change. Unless you like licking your lenses the Alpha can be ignored - the bodies outer layer of dead skin stops most of this.
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Forum: General Photography
08-29-2017, 05:46 AM
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The exposure is far too fast to get 2 distinct images from camera movement. There's no sign of blur on either of the images, so you can rule out camera shake.
I'm sure it's down to a reflection, if you only got it on some images I suspect the others were pointing more accurately at the sun so the reflection image is lined up with the other image.
The result is an impressive image.
:cool:
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Forum: Pentax SLR Lens Discussion
08-09-2017, 06:11 AM
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I like mine, but it is a bit heavy for carrying around, so only really comes out for motorsports & airshows.
A couple of my favorites with it from my old K7:
At 500mm where it's reportedly slightly soft (that probably not helped by my panning)
 IMGP5678small by Mike Kanssen, on Flickr
And over a much longer distance:
 Wind power - old & new by Mike Kanssen, on Flickr
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