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04-15-2014, 09:04 PM   #1
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Pentax 50mm 1.8 vs Sigma 17-50mm 2.8

Hey guys,

New to the forum and new to Pentax. Decided to sell all my Nikon gear and pulled the trigger on a new to me platform by picking up a K3 from B&H. The battery grip and 50mm lens in a package with the camera really solidified my decision. At the time, B&H had a nice sale on the Sigma 17-50mm 2.8 so I picked one of those as well for the obvious reasons. However this got me thinking if it is worth keeping the 50mm as the sigma, although the slower lens, already covers that focal length. I went through a lot of my photos to find that I actually rarely shoot at 50mm. 80% of my shots were on the wide end (marketing, advertising, promoting, modified car shoots, modeling and rarely some portrait shots). The Pentax lens is fast, loud, sharp and light. The sigma is sharp, heavy and covers wider focal lengths.

What's your take on both lensesat 50mm and is the nifty worth keeping?

Thanks in advance!

04-15-2014, 11:21 PM   #2
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First, hi and welcome to the forum!

No personal experience with the DA F1.8 or your Sigma lens but if you are not in need of any extra cash a fast 50mm might come in handy someday.
You might not use it now but maybe two months from selling the lens you will be in a situation where you need it.
I would w8 sell it. I am sure more people will come with similar opinions.

04-15-2014, 11:39 PM   #3
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I agree with the above. That 50 f/1.8 is probably only worth $70 or $80 used so won't get you much. On the other hand, you may have a day where a small, light lens with an extra 1-1/4 stop will make the difference. I have used my FA 50 mm f/1.4 inside museums where flash and tripods were prohibited and I really didn't want to push the ISO that last stop and a half. It doesn't take up much room in the bag and might come in handy. Plus, the very shallow depth of field makes for some interesting creative opportunities.
04-15-2014, 11:49 PM   #4

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You need at least one fast lens like that. So if you're not planning on picking up something like a DA*55, FA77, or FA31 (which are all excellent) anytime soon, you should keep it.

Rather than selling the DA50/1.8, I'd add a DA35/2.4 and practice using it wide open. Then start saving up for a used DA*50-135 or a FA77 (assuming you don't have the budget right now).

The K-3's a very good camera. Within a reasonable amount of time you'll be building a lens kit that costs 2x or more the price of the body, I trust. In the mean time, find an A100/2.8, K50/1.2, A24/2.8, K200/2.5, or something like that. I doubt you'll be wanting to change systems.

If you have any hesitation in spending more right now, the Sigma 17-50, DA50/1.8, DA35/2.4, and F70-210/4-5.6 (used - either Pentax or Takumar version) are quality lenses that are a great way to get familiar with the system.

Last edited by DSims; 04-16-2014 at 12:00 AM.
04-16-2014, 03:25 AM   #5
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Well only you can say if you need a lens or not. I would keep the 50mm mostly for its f1.8 aperture and for its light weight. When I travel I always take a "fast" lens with me for its low light performance. You won't get much for it anyway, since it is so cheap to buy as new. I also think the DA 50mm should deliver higher quality photos in a studio-type setting. Even an older used F or FA 50mm will cost more.
But feel free to sell the lens(es) and get something like the DA 12-24mm. Or even the DA 35mm ltd macro! Well loved lens, very sharp, and its a true 1:1 macro, which is great for product photography. The best part of an interchangeable lens system is that you can get the lenses that fit your needs
04-16-2014, 07:08 AM   #6
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I'll nail my colours to the mast straight away: I think the 50 is an amazing lens.

I'd pick it when I want something sharp enough corner-to-corner
I'd pick it when I want something unobtrusive
I'd pick it when I want something fast

Best of all, it's all three of those things in one package and it's very cheap. It's probably the best value lens out there. Which was one of the big reasons it was the first lens I bought as well. Downsides to it are:

It is only 50mm - so not always ideal (but don't forget your feet can zoom in many cases!)
There are sharper lenses (although questionable as to how noticeable the increased sharpness is?)
There are faster lenses
There are even less obtrusive pancake lenses

For you, it's about weighing up the pros and cons and deciding which is more important to you. My equivalent of your Sigma is a cheapo kit 18-55 WR lens, so there's no way I'd ditch my 50 and be left just with that as it's much slower and less sharp. I do have a nice DA* 50-135 and I reckon I use my DA* 50% of the time, my 50mm prime 40% of the time and my WR 10% of the time. There's no way I'd just stick with my DA* though - even though I could, I'd miss having a small (and slightly faster) lens.

Why don't you try forcing yourself just to use your 50 for a week? See how much you enjoy or hate it by the end of that and then decide?
04-16-2014, 07:50 AM   #7
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It's not only worth 70-80 dollars. More than 100, usually you see them going used for 130 asking price. Still, not a lot of money for a lens that can give you wonderful portraits with very nice bokeh and subject separation (about 75mm equivalent on 35mm format). I'd stick with it for a while and try to use it on portraits and other similar type shots. Its fixed focal length will force you to stay away from your subjects for portraits, and I think you will see that you might end up taking better, more natural looking portraits because of it. Focal lengths like 35mm or shorter will distort the face a little bit, and under 24mm will distort it quite a bit (bigger nose and forehead than in real life).

This is a good read about this subject (with photo examples):
04-17-2014, 05:53 AM   #8
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I decided to run some tests on both lenses to see how they compare. The focal length on both appear different. Possibly because the Pentax is actually 52mm? Bokeh looks almost identical on both. The Pentax is really not that sharp at 1.8. I'll run a few more tests and post pictures comparing the two.

However, the Pentax does seem like a keeper.


04-17-2014, 11:26 AM   #9

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QuoteOriginally posted by critical_gp Quote
The Pentax is really not that sharp at 1.8.
I haven't used the new 50, but the older AF 50s all needed to be stopped down to f/2 (or most of the time at least f/2.2) to get reasonable IQ. So try it at every 1/3 stop, and expect f/2.2 to (probably) be decent. Also, try Live View to make sure the focus is exact when testing. You can adjust the AF fine adjustment (for when you're using the viewfinder) for this lens later.

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