I think the largest concern outside of which lens to use would be...

Which iso to go with, or to use an automatic iso setting. Something that will show up considerable is the w/b and/or color temperature issue sue to multiple types of lighting.

The K5 used in this manner should be able to adapt somewhat, but... It would be best if one were able to somehow practice with the dress used for the bride. Practice, experiment, and do all of that ahead of time, and then lock in the setting based exclusively upon the brides dress.

Given some examples I've seen by various people using a K5 for wedding and portrait work, that the examples sometimes tend to lean towards a bluish cast. Although this is also easily correctable in editing after the fact.

Factors that make a difference when enlarging a print; especially to a larger sized print.

1. By far the largest factor is sensor size. I say this by example. I own a Canon with a 50mp sensor. The Canon has it's own specific market nitch, yet... When one has the ability to do studion work with an almost equal (mp count) Hasselblad with a 50mp sensor... There is simply no comparison between the ability to enlarge the image. The same can also be stated with a Pentax 16mp sensor, compared to a Canon or Nikon full-frame 16mp sensor. Ask any printing professional for very clear proof and examples.

2. ISO makes a difference. Obviously one would see a considerable difference between iso 100 and 1,000. Try to use the best iso that the subject will allow.

3. Differences in subject; at all of the same camera setting, try comparing a wedding enlargement to a still life. Due to tones, items such as fabrics, etc... The wedding is by far usually one of the most difficult subjects.

4. Editing software used, sadly for the wallet CS is still the best.

5, Add in items such as color calibration.

6. Printer hardware. One gets what one pays for. Try borrowing the use of some of the best in consumer printer hardware out there, then compare it to a true custom lab. Also experiment with printing surfaces

Even with the sizes of most current computer hard drives, that not everyone has that large of a computer hard drive... That stated, please remember; if one happens to have a computer platter type hard drive, that hard drive will need to be at least twice the size of any camera memory card.

Try to defeat that rule with mot computers; then one will run into issues when trying to defrag a platter hard drive

But imagine being stuck with the DFA 50 as the only lens in that range, or worse yet - ones only lens.

It's not bad for non moving or non people subjects but... The amount of focus hunting makes it one of the worst examples of Pentax AF - ever. The amount of times is focus hunts regardless of camera settings, lens setting, and subject, and also the length of time that the focus hunting operation takes. It almost better to use this DFA autofocus lens in purely manual focus mode - probably even a faster mode of operation

I own all of the DFA macros, but they are also very rarely used, not quite worst taking up the space in any sized gadget bag.

For 1stDSLRdude, and everyone else...

A few facts about those lenses mentioned... The Pentax 55-300 = great because it has WR, not so great for aperture and not a full frame zoom - if one wants to possibly upgrade camera bodies later. To my understanding both the Sigma and Tamron you mentioned should be full frame zooms, but no WR.

Might also want to consider waiting. The Sigma 18-300 should be available for all markets soon. About six months from now one may very well be able to expect two more Sigmas... Expect to see a 14-400 and also a 24-300 f2.8

Is that number correct? Four thousand one hundred ?!?

I got to see and even handle one of the prototype Pentax full-frames at a trade show not too many months ago. Based on that initial showing of the not quite full functioning full-frame... As it was observed then (and perhaps unless it is eventually changed once initially released... That the Pentax full-framer I personally observed was not a fill flash model.

Then again, the public will also most likely not see a public release version of the Pentax full-framer this year

I preferred to use a type of rubber lens hood if the angle of the lens permits it. But I've had many lenses retain damage with any of the variety of lens hood, rubber variety of lens hoods, or plastic compound, even variations of metal hoods.

Two worst examples... Sigma Green with custom made metal hood, receives hood damage so much that it had to be professionally removed at a shop. Leica f0.95 with built in hood; optics survived, but basically entire lens was replaced around it

Microsoft Surface better priced and speced out than any Ipad, all of them have better battery life than any current iPad, even the most modern Surface Pro with an Intel I7 chip has better battery life than any Ipad