You'll get a certain degree of
cognitive bias from me and maybe anyone else who has a DA*300, or is a prime lens snob.
I have no experience with the 150-500 and I've hand held and shot a couple of frames with the 50-500 OS version.
The 50-500 especially the OS version is generally accepted as being better than the 150-500.
This is where the
Choice supportive bias comes in. I had pretty much decided on the DA*300 so when i decided to compare it to the heavier 50-500, I "remember" quickly deciding that it was WAY too heavy for me. (I'm sure some people find it perfectly easy to hand hold).
The other thing I didn't really like about the 50-500 is that it is slow, as in it's at max aperture f6.3 from about 210mm mark to 500mm. When you are shooting these long focal lengths you need all the shutter speed you can get. I had a K-7 at the time and I didn't want to bump the ISO up an extra 1 1/2 stops to the world of grainy noise. The 150-500 top out f6.3 from about 290mm up. Both are slower than your DA55-300.
After buying the DA*300 i marvelled at how fast and sharp it is as part of my
post purchase rationalization overlooking the fact that I couldn't zoom out to anything wider or have anything longer than 300mm (a length which I already had covered with the 55-300).
This led me to searching and then paying a highly inflated price for the rare
1.7x-AF Adapter on ebay.
The 1.7x AFA works really well with the DA*300 (there's that post purchase rationalization again). The DA*300's SDM system is disabled and the short throw of the AF adapter mean the focus is attained very quickly. The only trade off is that you have to pre-focus generally in the range that the AF adapter will cover.
If you have a K-5II or IIs (and maybe the K-30) these have an expanded AF tracking area in the AF-C mode with the DA lenses. This doesn't work with the AFA attached and you are limited to the centre focus point so you have to keep the moving subject in the dead centre or the AF goes "zip-zip" through the range an you've lost it.
There are other TC's like the
Tamron 1.4x PZ-AF and the
Kenko Pz AF 1.5x Teleplus SHQ.
These use the SDM in the lens itself to focus. I have read that these do mis focus sometimes or require an addtional press of the shutter or AF to attain focus. Have a look at the reviews. These will get you 420 or 450mm, The AFA 1.7x gives you 510mm.
Now I have a "gap" of top quality glass between 100 and 300mm. The DA*200 and DA*60-250 have both been considered at one stage or another but i have not succumbed to LBA.
(Actually scratch that.. i did just buy an FA31 yesterday
) I'm sure there's a cognitive disorder term for that too.
I've got no complaints with my DA*300 except sometimes the bokeh behind the subject in backlit or contrasty situations
like this example -link- could be a bit smoother but I couldn't tell you another equivalent lens that could be better in that regard.
As a post script the B&H newsletter I got today shows Canon released a 200-400 f4 L lens which has a built in 1.4x converter so it can be switched instantly to a 280-560mm f5.6. All you'd need is a used 7D to serve as a rear lens cap. Oh and it's $11,800.