KentG

Its lands not lans (maybe just a typo you missed). There are several types of rifling each of which, as technology progressed, brought their own advantages and disadvantages. Usually in accuracy or...

Some of those Ricoh XR-1 "advantages"were negatives as far as I was concerned. Easier to handle meant cheap lightweight consumer build. If you didn't like the LX viewfinder you could put a...

Yes those Gold LXs are valuable. None of them were actually sold as they were presented to various people responsible for Pentax sales over that time. Some have shown up on the used market in the...

Yes if they want to compete because there are plenty of pro areas a MF camera just can't do the job, like sports. Not saying they should however. Kent Gittings

Yes they do and here is its modern equivalent, the Sigma 1000/8 EX APO, used as a video...

Ditto, scaling is meaningless because the number values between different brands and sensors is meaningless as the testers will tell you. There is no meaningful "scaling" you can do. The only thing...

Trust me on this, a dedicated macro will be much sharper than any zoom lens. Even a 3rd party macro will be better for macro than say a 100-400L. The speed gives you much better DOF control choices...

Probably if its not too big. I use the Clik Elite chest rig that has the built in monoball rail. I can actually jam my 60D + VG + Sigma 100-300/4 inside but have to use my smartphone with my Eye-Fi...

I know I just bought one off a person listing some Canon lenses on Astromart. I picked up a near mint Kenko Pro 300 1.4x for $125. It really works well on my Sigma 100-300/4. Even the corrected...

Probably not but Canikon users have the Kenko Pro 300 DG as an option. A lot cheaper than the factory ones and optically pretty close. Until I got one I didn't know how much better than the Sigma...

I have a pair of TCs, 1.7x and 1.4x, in Minolta AF. One is a Rokunar and one a Promaster and I can tell they were made in the same plant, and 99% sure it was Kenko. They look identical to the Kenko...

Then find a Sigma 100-300/4 in PK mount if you want the best of both worlds, primes and zooms.  No zoom with a ratio of 4x or more can equal a prime or a 3x and lower zoom lens. And I include the...

Try looking at Photozone's test instead, both real world images and MTF50 charts. The 55-300 can only reach the Excellent level in the MTF50 test at 200mm and below. It barely gets a Very Good in...

Well said Mike, spot on. Kent Gittings

In my case I am more worried about compatability of the 70D with my old Sigma 100-300/4 EX IF. Has worked fine on my 20D, 30D, 40D and now 60D, but being a pre-DG lens it can't be firmware updated....

You are very weird Mike if you consider the donuts add anything positive to the photo. :^) It is in reality the pinnacle of negative bokeh because instead of blending the background into a soft...

Kenko makes auto extension tubes for Canon, Nikon, Sony Alpha, 4/3rd,s and Sony-E, but they no longer make them for Pentax AF. There are some in screwdrive AF in the used market. They no longer...

If you use a normal strap and place it over your right shoulder, or over your head on that side, with the viewfinder against your leg or side it makes it easy to just reach down and grab the camera...

As an addendum it is entirely possible that the Pentax 67 SMC 400/4  and the 100 SDUF II F4 telescope share at least a common optical design if not actual optics. Kent Gittings

Correct. The photo was taken by the rig in the previous picture, the Apogee 16 MP monochrome CCD imager and a Pentax 100 SDUF II, a 100mm F4 astrograph. A type of short focal length wide field APO...