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06-10-2010, 02:20 PM   #1
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I have searched and not yet found, zoom that is sharp at f2.8?

Hi all,

I have looked through all these links and also on DPReview and not found what i'm looking for. Or more accurately, I may have but... I just don't know it yet as I'm still very much a newb when it comes to DSLRs and my relatively new K-X.

My interest is to replace the 18-55 kit lens with one that is much more capable in low light, specifically around the house at all hours, kids plays in the auditorium (it's a fairly small auditorium and I'm usually within 30-40ft but the kit lens seriously struggles), etc.

Many hours of searching and have just about nailed it down to the Tamron 17-50 but is it sharp at 2.8? I read that others may be sharpest at something like 5.6 or so.

I dislike using a flash when I can afford not to and I'm not able to get sharp pics using the kit lens. Over say 35mm it does get better but not good enough.

Thanks!!

Drew

upgrade dilemma!
Pentax 17-70mm f/4 or Sigma 18-50mm f/2.8 or sigma 17-70mm f/2.8-4?
Upgrade from kit to 16-45mm?
Kit lens or DA 16-45mm F4.0 ED AL for my first Dslr K7?
Looking to replace my K-x kit lenses - recommendations please
Replacement for 18-55mm II kit lens
DA 16-45mm much better than 18-5mm5 DAL k-x lens ?
Tamron 18-200mm vs DAL 18-55mm
Kit lens replacement, going nuts
Sigma 18-50 or 17-70?
kx kit lens upgrade

06-10-2010, 02:41 PM   #2
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SMC Pentax DA* 16-50mm and DA* 50-135mm are both F2.8 zooms, both good wide open. They do sharpen up a little bit stopped down, but I don't think you'd be disappointed with the wide open performance if coming from the kit lens. Compared to a nice prime at F2.8, then zooms will lose, but they are both great zooms.

Of course, they cost decent money...I've never used Tamron or Sigma equivalents, so I cannot speak to those, but they are a little cheaper at least. A lot of people are really fond of the Tamron 28-75mm F2.8 zoom, so that might be worth a look if you don't necessary need real wide shots.
06-10-2010, 04:27 PM   #3
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QuoteOriginally posted by AndrewJ Quote
Many hours of searching and have just about nailed it down to the Tamron 17-50 but is it sharp at 2.8? I read that others may be sharpest at something like 5.6 or so.
Virtually *all* lenses are sharper stopped down a bit than wide open. That doesn't mean they aren't sharp at all wide open. Sharp is not a black & white thing - there are many shades of gray. If you want to get into trying quantify "how sharp" a lens is at a given aperture, sites like photozone.de can often help with that, but unfortunately they don't test these two specific lenses on Pentax (they test the older/inferior version of th 18-55, and they test the Tamron on another system but numbers aren't comparable across systems).

QuoteQuote:
I dislike using a flash when I can afford not to and I'm not able to get sharp pics using the kit lens. Over say 35mm it does get better but not good enough.
Might help to post samples. The kit lens, like most standard zooms, is actually sharper *below* 35mm than above. So whatever issues you are seeing below 35mm, it's probably not the lens - more likely simply not focusing accurately enough, holding the camera steady enough, or having a fast enough shutter speed to stop subject motion.

But it's certainly the case that an f/2.8 will be more suited to low light photography. Lens softness really won't enter it much - twice as fast a shutter shutter speed is twice as fast a shutter speed.
06-10-2010, 04:28 PM   #4
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Along the lines of me looking for a zoom that's sharp at f2.8 am I far off in thinking that if sharp there it should be similarly as sharp throughout?

I realize what I really need is a prime for around the house but I cannot afford both and I'll first need to fix what's bugging me most... the oem 18-55.

06-10-2010, 04:39 PM   #5
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Thanks Marc!

I see you are very active over here as well.

Ok, I vowed to get off my @$$ and start using my camera more. To the casual shooter that has just now gone from a point and shoot to a DSLR it's very common to shoot only when a situation calls for it and that typically means we are never quite ready.

I, knowing absolutely nothing, will take 5 or so min to take test shots until I get it right. When I have this kind of time my pics usually come out very nice (although, I also don't know a thing about proper or pleasing composure-that's for another thread).

Being ignorant, my quick shots are always worse than my wifes using her Canon D620.... Ouch.

What I'm getting at, eventually, is that I'm somewhat of an introvert and typically lurk. I don't mind posting up a shot if my extreme ignorance doesn't eventually get to you.

Possibly, over the course of a year I'd hope to be able to share a pic showing a dramatic difference for the better...you'll have to bear with me though.

I'll find a pic to embarrass myself with later tonight.

-Drew
06-10-2010, 05:27 PM   #6
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A good lens will always be a good lens, but getting to know your camera better (such that you don't have to think about what you want it to do...you just do it) is FAR more important.

When the time comes to buy a better lens (the kit lens is no slouch, but it's a catch all lens - not a specific lens) then you will know what you want and will be able to get the most out of it.

That being said, both my Tammy 28-75 and my DA* 50-135 are excellent lenses - even wide open, but I purchased them more for their focal length ranges (for what I shoot), their build quality, overall IQ, how they render an image, their bokeh ability, and feel. The bonus for me is that they are both f/2.8 lenses and are capable lenses in OK lighting.

c[_]
06-10-2010, 05:30 PM   #7
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Tamron seems to be very sharp at f2.8 based on photozone results.

Tamron AF 17-50mm f/2.8 SP XR Di II LD Aspherical [IF] (Nikon) - Review / Test Report - Analysis
06-10-2010, 06:56 PM   #8
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The 16-50 is quite sharp wide open -- except for a little bit of softness at the 16-18mm end. Of course, it sharpens up more when stopped down, but the biggest difference is that you get more border sharpness. Most lenses have pretty good center sharpness wide open (although not all), but the edges often suffer until you stop down a little.

06-10-2010, 08:22 PM   #9
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QuoteOriginally posted by pcarfan Quote
Tamron seems to be very sharp at f2.8 based on photozone results.

Tamron AF 17-50mm f/2.8 SP XR Di II LD Aspherical [IF] (Nikon) - Review / Test Report - Analysis
+1 to that. I bought it precisely for "around the house" photography. It has enough zoom for across the room, is 2.8, and has terrific bokeh. Stopped down to f/8 it is no better than the kit lens, though that extra 1mm at the wide end is good for wider indoor shots.

All lenses at this price point will have some softness at 2.8. It is unavoidable unless you want to spend serious $$$. Even then most lenses are softer near the borders.

For some of what you describe, faster shutter speed is what you need, and that's a flash solution. Bounce it off the ceiling and it's excellent for photographing kids. A wider aperture cannot help you for some of what you describe.

Primes for around the house? DA 35/2.8 macro, then DA 40/2.8. It depends on the size of your house :-)
06-10-2010, 09:03 PM   #10
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I give 2 thumbs up to the Tamron.
06-10-2010, 09:14 PM   #11
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QuoteOriginally posted by pcarfan Quote
Tamron seems to be very sharp at f2.8 based on photozone results.

Tamron AF 17-50mm f/2.8 SP XR Di II LD Aspherical [IF] (Nikon) - Review / Test Report - Analysis
I've been contemplating replacing our Star lens with the Tamron based on this review. Anyone know it is up to the task? We typically use a *16-50mm indoors, but... I've always found it to be on the soft side wide open and usually hold back a notch when using it.

So I was thinking the 17-50 might give us the edge to shoot wide open instead.
Comments on this?
06-10-2010, 10:09 PM   #12
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I can name several zooms that are sharp wide open, but I can't think of the last time I needed to shoot wide open at 16mm with my 16-50 - but at 30-50mm, there are many instances where f/2.8 was needed - and the results were great.

I also have the Tamron 28-75 which is awesome wide open at all focal lengths - and it too is a good kit lens complement (can't replace the 18-28mm range, clearly). But I can vouch that the Tamron 70-200, Pentax DA 12-24 and DA 55-300 are all stellar wide open also.
06-10-2010, 10:19 PM   #13
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I think the Tamron 17-50 is a superb lens and I have no hesitation using it wide-open. I prefer prime lenses, but this zoom is a great value. How much better it is compared to the 16-50, I don't know, but I've made my decision to get it based on the photozone reviews, and I didn't look back.
06-10-2010, 10:28 PM   #14
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The DA*16-50 has pretty good center sharpness wide open. The sharpness evens out more across the frame as you stop it down. Here are a few samples I've taken.










I don't trust it quite as much as I do my FA31 at f/2.8, but that's not really a fair comparison since the FA31 is wide open at f/1.8. I feel like the FA31 is clearly better until about f/4 and then they start to get very close after that.

I would very much recommend the DA*16-50 based on its image quality. The only reason I hesitate at all in giving recommendations on this lens is its problems with SDM.
06-10-2010, 10:38 PM   #15
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I don't find the Tamron 17-50 too soft wide open & the corner sharpness is reasonable.

I'm not sure I agree with Aristophanes in that the bokeh is 'terrific'. At first I didn't find the bokeh too bad, but the more post work I did, I realised it was slightly 'busy', but acceptable.
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