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01-25-2010, 01:28 PM   #1
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In the market for a fast prime

So I'm *possibly* in the market for a fast prime. I've been looking at a couple of Sigmas (20/1.8, 24/1.8, 28/1.4, 30/1.4) and the Pentax 50 1.4. I'm kind of torn between all of them.

A part of me is getting hung up on the crop factor and that's pushing me towards the wider Sigmas. But I've read that some of the Sigmas can be really soft around the edges. I've also read that the Pentax is softer @ 1.4 then it is at 2.8.

Anyways... what are you all's thoughts on some of the primes available?

01-25-2010, 01:38 PM   #2
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QuoteOriginally posted by imfinetoday Quote
So I'm *possibly* in the market for a fast prime. I've been looking at a couple of Sigmas (20/1.8, 24/1.8, 28/1.4, 30/1.4) and the Pentax 50 1.4. I'm kind of torn between all of them.

A part of me is getting hung up on the crop factor and that's pushing me towards the wider Sigmas. But I've read that some of the Sigmas can be really soft around the edges. I've also read that the Pentax is softer @ 1.4 then it is at 2.8.

Anyways... what are you all's thoughts on some of the primes available?
Take a look at "real world" sample images, too. Lenses (50mm and below) can have funny field curvature and aren't ideal for taking photos of ISO resolution charts or cereal boxes--one of the reasons why dedicated macro lenses look good on paper is that they have very flat field curvature. If field curvature is anything but flat, border MTF numbers won't tell the whole story. Also, it seems that there is sample variation among the Sigma's (optyczne.pl really liked their 20mm, but photozone.de's copy was a dud).
01-25-2010, 01:39 PM   #3
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QuoteOriginally posted by imfinetoday Quote
So I'm *possibly* in the market for a fast prime. I've been looking at a couple of Sigmas (20/1.8, 24/1.8, 28/1.4, 30/1.4) and the Pentax 50 1.4. I'm kind of torn between all of them.

A part of me is getting hung up on the crop factor and that's pushing me towards the wider Sigmas. But I've read that some of the Sigmas can be really soft around the edges. I've also read that the Pentax is softer @ 1.4 then it is at 2.8.

Anyways... what are you all's thoughts on some of the primes available?
The Sigma 50 f/1.4 is supposed to be sharp to the edges, but it's a pretty big lens. Nearly every lens is going to be sharper once it's stopped down. Are you looking for a sharp prime to use as a standard or walkaround lens?
01-25-2010, 01:40 PM   #4
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You just described a range of lenses from 20mm (pretty wide) to 50mm (pretty close). For anyone to really help, you'll need to expand on what your primary expectations for the lens will be. If you want a walk-around prime lens, then in my opinion, the 20mm would be knocked out for being too wide, and the 50mm would be knocked out for being too long. Many people find 35mm to be an excellent walk-around focal length, namely covered by the Pentax DA 35 Macro Limited. If low-light portrait work is what you are looking for, then the Pentax 50mm/1.4 is great. If you'll be doing a lot of landscape work, then the 20mm lens becomes more applicable.

Also, you can check the user reviews on this site for the lenses you are considering. These reviews are often a big help. Good luck.

01-25-2010, 01:46 PM   #5
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I don't do a whole lot of landscape-esque type of stuff. But i can't say that landscape doesn't come into play when I'm out and about. I personally find myself coming more toward the portrait side. I think at this point more of an all around standard lens would be good. I do find myself in a lot of low light situations lately where my current lens doesn't seem to be cutting it.
01-25-2010, 01:52 PM   #6
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My first fast prime was the FA 35/2, but till today, I rarely use it. I bought a fast fifty a little later and noticed that I like that focal range far more than 28-35mm. I'd either go real wide-angle (20mm), or real portrait (50+mm).
01-25-2010, 02:00 PM   #7
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The Pentax FA50 is definitely quite soft. I'd describe it as kind of "cloudy" at F1.4 (like you're in a dream). It's still a great lens and takes great shots at that aperture but they'll just have that slight characteristic.

I have a Sigma 30mm F1.4 (Which I am actually planning on selling soon. Upgrading to FA31 when I can!) and it's a fantastic lens if you get a good copy. Weak in the corners so it's not too great for landscapes for pixel peepers, but overall still takes fantastic photos of people, objects, etc. It is fantastic from F1.4 to F4 if your copy is good (Which mine is). Here is a shot I took with it:

Olympic Image #43 on Flickr - Photo Sharing!

Vignetting and post-processing done, so this isn't straight out of camera. But as you can see, it's quite a capable lens.
01-25-2010, 02:08 PM   #8
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QuoteOriginally posted by imfinetoday Quote

A part of me is getting hung up on the crop factor and that's pushing me towards the wider Sigmas.
Not sure what you mean by that.


But I've read that some of the Sigmas can be really soft around the edges. I've also read that the Pentax is softer @ 1.4 then it is at 2.8.
QuoteOriginally posted by asdf Quote
Take a look at "real world" sample images, too.
ASDF is right, reading reviews should only put you in the ballpark. You need to decide what kind of pictures you want to take and look at real world examples of similar images.

01-25-2010, 02:09 PM   #9
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QuoteOriginally posted by dugrant153 Quote
The Pentax FA50 is definitely quite soft. I'd describe it as kind of "cloudy" at F1.4 (like you're in a dream). It's still a great lens and takes great shots at that aperture but they'll just have that slight characteristic.

I have a Sigma 30mm F1.4 (Which I am actually planning on selling soon. Upgrading to FA31 when I can!) and it's a fantastic lens if you get a good copy. Weak in the corners so it's not too great for landscapes for pixel peepers, but overall still takes fantastic photos of people, objects, etc. It is fantastic from F1.4 to F4 if your copy is good (Which mine is). Here is a shot I took with it:

Olympic Image #43 on Flickr - Photo Sharing!

Vignetting and post-processing done, so this isn't straight out of camera. But as you can see, it's quite a capable lens.


Gonna sell it eh?

Lets say the subject (in focus) is off to the side of the frame. How does the 30 do there? Is it just always soft?
01-25-2010, 02:11 PM   #10
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There are more faster and cheaper lenses available around 50mm than around 28mm. If you don't mind manual focus and stop-down metering, you can get a 50/1.2 Pentax or a 55/1.2 Cosina, somewhere around $250-350. You can trade price, speed and convenience features to get exactly what you want from $25 on up through the Pentax-DA 55mm f1.4 with weather seals and SDM.

At 28-35mm, fast choices (let's say f2 or faster) are limited. The Sigma lineup looks very competitive on paper, and I think they are well-priced. Pentax has a DA35/2.8 lens that's not fast, an FA35/2 lens in short supply/high demand, an FA31/1.8 that's quite pricey, and some long-out-of-production glass in high demand.

Of these focal lengths on APS-C, 35mm feels the most like a normal lens to me. I have a couple of older fast 28mm f2.0 or faster lenses, and they still feel a little wide. I just got this, an older manual-focus model of the Sigma 28/1.8, after looking at the AF version a lot:



It's already a hefty lens. I can see why the #1 issue with the AF version is size. I haven't used it enough to really compare it to other choices, and they are somewhat rare. I think it's odd that the AF version has been out for a while, gets very good reviews and no more detractors than any other lens, has less and less direct Pentax competition every day, yet few people buy one.

If you have the kit lens, it should be a good tool to select focal length. Just try to live with one focal length for a while. That will at least limit your search to one range.
01-25-2010, 02:14 PM   #11
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QuoteOriginally posted by imfinetoday Quote
I don't do a whole lot of landscape-esque type of stuff. But i can't say that landscape doesn't come into play when I'm out and about. I personally find myself coming more toward the portrait side. I think at this point more of an all around standard lens would be good. I do find myself in a lot of low light situations lately where my current lens doesn't seem to be cutting it.

Based on what you say here, the only suitable lens in your list would be the 50 1.4 .
You might get away with a 30mm but people tend to get uncomfortable when you get right up in their face to take a picture.
01-25-2010, 02:15 PM   #12
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QuoteOriginally posted by Damn Brit Quote
ASDF is right, reading reviews should only put you in the ballpark. You need to decide what kind of pictures you want to take and look at real world examples of similar images.
When i mentioned the crop factor... I was meaning since the 20 (etc) is wider it would translate into 32 when you take the cropping into consideration, where as a FF would be a true 20. (I think I just confused myself explaining that) Maybe that's just my deceived thought process on anything that's not a FF.
01-25-2010, 02:17 PM   #13
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QuoteOriginally posted by Damn Brit Quote
Based on what you say here, the only suitable lens in your list would be the 50 1.4
How about the FA43/1.9 Limited ?
01-25-2010, 02:23 PM   #14
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QuoteOriginally posted by Damn Brit Quote
Based on what you say here, the only suitable lens in your list would be the 50 1.4 .
You might get away with a 30mm but people tend to get uncomfortable when you get right up in their face to take a picture.
Just maybe he should take a look at the DA 40/2.8 as well, which I know is not in the "fast" range he prefers, but is a more versatile focal length than 50mm imho, and isn't "slow" either. Or at least expand his 50mm search to the usual suspects for more options, namely the f1.7 versions. The F and FA 50mm/1.7 lenses are very highly regarded, and sharper than their 1.4 cousins, but are still good deals at their going rates (around $200 or so used). Food for thought.

Edited to add: RBellavance's suggestion of the FA 43 is also a viable option, though more pricey of course.
01-25-2010, 02:24 PM   #15
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QuoteOriginally posted by imfinetoday Quote
When i mentioned the crop factor... I was meaning since the 20 (etc) is wider it would translate into 32 when you take the cropping into consideration, where as a FF would be a true 20. (I think I just confused myself explaining that) I think you confused yourself because you don't know why you're needing to explain it in the first place.Maybe that's just my deceived thought process on anything that's not a FF.
Forget about the crop factor, unless you are going to take duplicate pictures with a full frame and a cropped sensor camera and compare them you can ignore it completely.
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