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04-05-2010, 10:24 PM   #1
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help me make up my mind: Pentax FA 50mm f1.4 vs Tamron 28-75mm f2.8

Dear Pentax experts,

as I am getting better at my K-x and its kit 18-55mm lens, I've been thinking of putting my DA L 50-200mm up for sale and look for a fast used lens for my indoor, night photography. I am very comfortable using the kit lens as my general purpose lens and wants something faster for my dinner/party photos at night, and I find very limited use for the 50-200mm.

after reading through numerous posts, I've narrowed down my choices: Pentax FA 50mm f1.4 vs Tamron 28-75mm f2.8

here are my reasonings for each lens:

Tamron 28-75mm:

- i will use it as the general purpose lens, and save the kit lens for wide angle group photo. so i think i get more use out of it for the (more) money spent
- less frequent lens changing

- more expensive
- a LOT heavier
- f2.8 may still not be fast enough for my purpose of night shooting at dinner and parties...

Pentax FA 50mm

- cheaper than the 28-75mm
- lighter and more compact
- better image quality (i think/hope)

- less usage for the money spent (i've never used primes, so maybe this will change...)
- 50mm is longer than my intended usage of dinner/party photo
- not as versatile

my top concern is if f2.8 will be fast enough? and then is the issue of its weight/bulk

I hope I have explained my situation clear enough for you to help me make a choice

thanks in advance


p.s. maybe I should even sell the kit lens and get the Tamron 17-50mm f2.8?

04-05-2010, 11:32 PM   #2
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The basic answer is simple; if the 50mm is the wrong focal length (too long), don't buy it.
04-05-2010, 11:44 PM   #3
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Love my 50mm Pentax, rarely comes off my K7. Loving the primes now, don't really miss having a zoom at all.
About a month ago I bought the Sigma 30mm 1.4 which is an absolute cracker. I bet the 31mm Pentax is beautiful too.
Personally these primes have been so fantastic to use (low light, bokeh, small) that I can't see myself going back to a zoom anytime soon...
04-06-2010, 12:19 AM   #4
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For dinners, parties, ... you'll find that 28mm oftentimes is not wide enough.

I'll say get a 17-50mm F/2.8. The 50mm F/1.4, though nice, is not practical for dinners, parties because of its long focal length. Also, at F/1.4, the DOF is too thin for that application. You'll need to close down for decent DOF any way.

The K-x has pretty good sensor for low light. Just crank up ISO if needed and reduce the noise in post-processing.

04-06-2010, 04:40 AM   #5
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Get the Tamron (or, better, the Tamron 17-50). With only a 50mm prime you'll miss a lot of shots. Primes are excellent if a) you have a collection of them that covers the focal lengths you use most, and b) you are not in a situation in which you need to change them quickly and frequently.
04-06-2010, 04:55 AM   #6
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tammy 28-75/2.8 gets my vote

As nice as the FA50 is, you'll have trouble with group shots at that focal length. Either it's too long for the required Field Of View, or DOF is so narrow. Even at F3.2, the DOF will still be pretty shallow for, say, a group shot of 3 people (that are not perfectly aligned the same distance from your camera).

Anyway, the K-x is "fast enough," even with the Kit lens (which is pretty sharp already btw)
04-06-2010, 05:41 AM   #7
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I'm going to echo the sentiments of those above and say that the 50mm F/1.4, especially on APS-C, is going to be way too long for what you want. Between the two you've selected, I'd go with the Tamron all the way.

I'd also suggest, if you never plan to do shooting on an older film camera, that you look at the Pentax DA 14mm f/2.8, or the Sigma 20mm F/1.8. If you want a fast, wide prime, there's your best bets.

You may also look for example on eBay at some older AF/MF film lenses...those may do the ticket too, for a lot less than you're going to spend here.

04-06-2010, 07:15 AM   #8
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When lens speed is an issue, that usually means that the primary use for the lens is going to be indoors. Indoors, you can almost always get closer to your subject if necessary. It isn't always possible to get far enough away. You will miss more shots indoors due to a too long prime than you will from a shorter one. Even if the shorter lens is a little slower than you would like, I would prefer to bump the ISO and have the entire picture that I wanted with a little extra noise rather than miss it entirely because I couldn't fit everything in.
04-06-2010, 08:48 AM   #9
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Original Poster
thank you all for the replies, seems the fast zoom is the more logical choice.

since the K-x is my first DSLR, and for the lack of comparison, I am taking its (and kit lens) light weight and compactness for granted.

interestingly, nobody brought up the issue of weight and bulk of the tammy.

should I be concerned with it?
04-06-2010, 11:10 AM   #10
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QuoteOriginally posted by macky112 Quote
since the K-x is my first DSLR, and for the lack of comparison, I am taking its (and kit lens) light weight and compactness for granted.

interestingly, nobody brought up the issue of weight and bulk of the tammy.
How much bigger and heavier is the body + kit lens compared to the body + Tamron 17-50?

I have a Sigma 18-50 F/2.8. It is probably similar to the Tamron in question. The Sigma is significantly bigger and heavier than the 18-55 kit lens.

But the K10D + Sigma is not much bigger and heavier than the K10D + kit lens.

The Pentax DA* 16-50 is a different story. It is significantly bigger and heavier.
04-06-2010, 10:59 PM   #11
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I don't think anybody really cares to much about weight and size in this category of lenses. If one cares, I guess one will use DA LTD primes.
04-07-2010, 09:33 AM   #12
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Keep in mind that every lens purchase involves compromise. There is no 10-600 f/1.2 lens that has astonishing image quality at all focal lengths and all apertures, has macro capability, is weather-sealed, and sells for under $200. Doesn't exist. So no matter what you get, you have to give up something: you might prefer speed but pay more, or you might prefer focal length but give up a little on speed. Compromise is inevitable.

If you are looking for a single multipurpose lens, then I think you need first to ask yourself what kind of pictures you plan to take most often, and then find a lens whose compromises work best for you. The problem I have had in the past is, I sometimes don't know what I really want, until I find it. When I bought my first DSLR four years ago, I thought the longer focal lengths were what mattered to me. Over time, I've discovered that I want wide way more often than I want long. If a weird mugger demanded either my Tamron 70-300 or my Sigma 10-20, I wouldn't hesitate for a second to hand over the Tamron and keep the Sigma. But I never have guessed that when I first started shooting with a DSLR.


The Tamron 28-75 f/2.8 is certainly the most versatile of the three lenses you're considering. It would make Goldilocks happy: it's not too wide and it's not too long, it's not too fast and it's not too slow, it's just right. It has good very good image quality. It's not terribly expensive. I'd say it is not just the safe choice here, but very likely the best choice, given the way you described how you want to use the lens.

The Tamron 18-50 f/2.8 is also a good choice, if you want wide more than you want tele. It's a tough choice. I'm not sure that 18 isn't more important to me than 75. I might go with the 18-50, especially for my personal photography. For work (weddings, portraits) I would without hesitation prefer the 28-75.

And if you decided that you wanted a prime lens instead of a zoom? I can tell you that I would NOT pick the 50 f/1.4 as my one lens. I know this because, while I own this lens and love it, it simply doesn't get used all that much.

In my view, the nearly ideal prime would be one I can't justify spending the money for right: the Pentax 31 f/1.8. On a 1.5x crop factor camera like our Pentax DSLRs, the 31's angle of view is very close to "normal" (and therefore just about perfect as a daily use lens for me). It's fast. Image quality is supposed to be awesome. It's small and apparently amazingly well built. The compromise is that it costs an arm and a leg.

Of the primes that I own (21, 28, 35, 40, 50, 70, 105), the ones I use most often are the Pentax 40 f/2.8, Sigma 28 f/1.8 and now the Pentax 21 f/3.2. If I had to pick just one of these, it would probably be the Sigma 28.

04-07-2010, 08:16 PM   #13
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I console myself with the observation that the 31 is *not* actually all that small, at least compared to all the the other limiteds. But I suppose it's probably smaller than the Sigma 28/1.8.
04-07-2010, 09:16 PM   #14
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For me, I will get the Tamron 17-50 f2.8.
With only a 50mm prime (unless you have others like 31mm or 28mm) you'll miss a lot of good shots unless you have time in your hand and you move away or nearer the subjects.
04-07-2010, 09:17 PM   #15
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The 28-75mm, as I said in another thread, is the only lens I've ever seen go up dramatically in price on the used market. Over the last year a lot more word about it has gotten out, and lots of people are realizing how awesome of a lens it is. If you can find it for a good price, then I'd totally recommend it instead.

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