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Forum: Pentax SLR Lens Discussion
09-04-2014, 11:49 PM
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A teleconverter would be good in that case. But get a good one. Teleconverters can really make a good lens look bad. There aren't many af options. The new hd one is pricey but probably the best option. The kenko 1.5 is much cheaper and has generally good reviews.
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Forum: Pentax SLR Lens Discussion
09-03-2014, 09:35 AM
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Assuming you're at the 135 end, not the 50...
minimum focus distance
No tube: 1087mm
9.5mm tube: 864.1mm
19mm tube: 746.4mm
28.5mm tube: 675.7 mm
57mm tube: 577.9 mm
Of course, you're losing a lot of depth of field when you add tubes.
Another option, but probably not a good one for what you're trying to do... but if you really want just a *little* bit more minimum focus distance, increase the aperture so you have more depth of field.
At 2.8 and 43 inches you have about 1/10 of an inch in either direction. At f/11 you get almost a half inch in either direction.
neither of those seem like sufficient depth of field for a decent portrait.
So maybe you're using 50mm. At 2.8 you have a bit under an inch in either direction, and f/11 gives you a bit over 3 inches in either direction.. your subject could move forward a couple of inches. You'd have to flip focus to manual and set it to the minimum, but you'd get that extra space. At f/22 you'd get a full 6 inches, but probably have diffraction.
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