well primes are worth it for me, it's my job to pull nice shots out of situations where the other guy comes up with a dud.

but the 100mm macro would be be a nice addition to your kit...
don't let me talk you out of the lens buying affliction....

in a word, no.

Skill, composition and lighting make for a better photo, with any lens.
photographer errors like the one you mentioned will bite you with any lens.

now a fast prime may have four noticeable DIFFERENCES over your kit zoom..

1) boke, the out of focus areas may be more pleasing
2) DOF at wide open apertures may be more pleasing..
3) ability to manually focus and auto focus in low light may be better..
4) sharpness increased will be noticeable when printing huge enlargements..

but...

for most shots that are not going to be printed larger than 11x14,
you should be able to get many fine shots with the lens you got......
and stopped down from wide open, a good shot from either lens will be hard to tell one from the other...

I'm leaning towards the 21, but holding off til the new cameras are released to see what's coming..

70 is a tad long for general walk about.

of all the gear I own, nothing gets used as much as my fast fifties.....

then the 16-45, then the 100 macro, 10-17, 85mm soft, 28-70 f4

I use mine mostly in studio,or indoors, low light, hence the desire for primes, followed by constant aperture zooms...

John's advice is very sound... buy something that adds to your capabilities first before you buy something that duplicates what you already got.

I went with the 50 1.4 and 100mm macro, have been so happy, I couldn't justify any of the inbetween lengths...
so I'm considering something in the 20-35mm range when I buy my next camera body...

none of those aps have been rated...at that price, i'd wait for some reviews.

I was bad...
shot this with sony:
link

seriously... it's depressing.

I didn't think I was posting in the wrong thread.. if you are bored and need a project, that is definitely a worthwhile endeavor, to document your possessions and gear.... takes up a couple hours at least to get everything done.

sea and sea make some fine underwayer gear as well..
link

ewa marine:
link


and yes o-rings do need maintenance or they will fail...

Program modes allow ev control...
manual does not if you want to over or under expose, you are in manual to use the aperture or shutter or iso settings to control the exposure, the camera will not "Auto" ajust anything for you...
you can however set up your "Auto Bracketing" feature in manual...

I use my flash and my camera BOTH in manual mode 95% of the time.

I use radio slaves and off camera dedicated pentax cable kits as well.

occasionally aperture priority, and auto flash, or p-ttl.

my wife uses the wireless p-ttl

we both get results.

when using the flash on manual, it helps to think of the flash as a second light source.
you got the ambient lights as one (tripod helps) light source.
you decide which one will be your main light source, and which one will be your fill.

if I want the ambient to be fill, I set my camera up to slightly underexpose for that light, then set up my flash and dial it in for a proper exposure on my subject.
the wedding shot above was done that way.

if I want my main light to be the flash, I set my aperture and shutter on the camera to severly underexpose the ambient light then set up my flash and any reflectors to create the lighting effect I want on the subject.
that is what I did with the roses above, (my living room was a little cluttered, so I made it go away.)..