how much better would a 50mm prime really be?

I have a Sigma 18-200mm DC 3.5-5.6 atm and use 50mm focal length for alot of protaraits i do

i'm just wondering how much better a 50mm 1.4 would really be?

the images i take are aready really good and sharp and have plenty of detail i my opinoion

i'm just not sure that spending another three hundred dollars to upgrade to that lens is really worth it

whats the difference really? apart form the faster aperture steting which really isnt' all that useful anywya, because f5 is enough, but i guess it would help in low light situations i guess

heres a sample pictures from my 18-200 and i think its perfect. how much better can it possibly get?










cheers fellas

Rather than repeat it all, there is a thread here with several opinions. https://www.pentaxuser.com/forum/viewtopic.php?t=5823&postdays=0&postord...

Bottom line is that you are comparing chalk and cheese. A prime 50 will blow away the images of such a long range zoom.

Kim

Both the above images are reasonable quality (although I'm not convinced about the colour cast in the first one) but neither look to be really, really sharp of have any real bite to them - something much easier to get with a faster, sharper prime.

I have to strongly agree with the above two posts.

Yours pictures are very good, but using a Pentax 50mm 1.4 will be a revlation.

I haved used one for many years with a MZ3, then the istD and now K10D, and it is by far my favourite lens. Great tones, depth and control and brilliant optics and can be ued in virtually any light, can't sing its praises highly enough.

Amer

Can you really tell this at web resolutions?

If you only want to put 800 pixel wide images on the web, just about any lens will do and it will be difficult to tell the difference. Take the same picture on a "kit" zoom then a good 50 prime (The Pentax ones are generally all good. Print both up to 10x8 and the difference will be very obvious.

Kim

I believe you.

It just bugs me more and more (almost to the point that I have to pour myself a second glass of wine) when I see anything (other than a 100% crop, obviously) posted on a web forum, with people claiming that it shows anything at all about the respective sharpness of the lenses in question.

People here aren't often guilty of it, but there's another forum, not a million miles away, where for the sake of my blood pressure I've just had to stop reading it because of all the

"here's a picture"
"ooh, nice crisp sharp shot"

... and similar rubbish you read, when actually they're noticing contrast, USM, or just the fact that four pixels collapses to one when you quarter the linear dimensions of the rendition.

Sorry. Rant over

Chris,
That is why I tend to believe my own experience with lenses in a real world enviroment rather tham MTF graphs etc. I also try to base any advice on what I think will suit the person rather than suit the way I shoot.

Kim

Sure. When you have the right sort of experience, I don't doubt that it's reliable.

However, I know I don't. And I also infer from what some people write elsewhere, that they don't either.

So what's a relative newbie like me to do?

Experimenting for oneself gets expensive once you get past the consumer-zoom price point.

That's a tough one to answer, ChrisA. Maybe there is no easy answer.

However, probably you can be relatively sure now of the various qualities of many pentax, Tamron and Sigma lenses in particular that have been extensively discussed here.

I don't know if you are aware of www.photodo.com which is a sister site to this one and all about lenses. There are extensive tests there and also owner reviews as well.

See you there?

I'm fast coming to the conclusion that you're right.

Indeed, and I'm very grateful for both the informative posts from a good number here, and also for the way some of you guys put up with me banging on about things until I gain some level of understanding.

Aha. I wasn't, but I am now. Maybe the next key in the puzzle. It's like Half Life, or Far Cry, but without all the shooting. Well, a different sort of shooting, anyway.

Thank you, yes.

Chris,
I have a fair amout of space on my website. As you may have gathered, I also have a few lenses. If you need to look at the results of any, I can always upload the raw file to the site for you to download. At least then you won't be basing a judgement on an 800 pixel wide image.

Kim

...and of course if the South and London User Group (SLUG) ever met up again, you'd be more than welcome to try out any lens I have.

Dan

To play devils advocate for a mo:

I thought portraits shouldn't be too sharp.

Or is it only to be sharp where you want it to be sharp?

i dont know, tack sharp is always good in my opinion

but i dont know how a lens can hide the skin imperfections of a subject

but i can fathom that it can make an image "softer"

i suppose ill understnad when i get one

and isn't 50mm a bit to small?

i like doing my mug-shots like the one above

should i go for teh 70mm or the 77 instead

ineven though thy're twice and three itmes as much