Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
12-15-2013, 07:55 AM   #1
Site Supporter
reivax's Avatar

Join Date: Jun 2011
Location: California
Posts: 736
Pentax FA 50 1.4 vs Sigma 17-50 mm 2.8 at 50mm

I'm taking some portraits later this week and I was debating on whether or not to use my Pentax FA 50 1.4 or to use my Sigma 17-50 2.8. I was pretty set on using the prime, but for curiosity's sake, I decided to look up some test scores on lenstip. I have to admit that I'm a little surprised at seeing the zoom had better scores than the prime. Is this accurate?

I've always tried to use primes when I do any kind of portraits, but if the Sigma is actually going to give me better results, then I'm not sure why I would want to use the 50 mm. I know the prime is a lot faster and it's also more compact, but if I don't need to go to faster than 2.8 and weight/space is not an issue, why would I want to use it over the Sigma? I am hoping that I'm reading the tests wrong and that someone can enlighten me. I am really disappointed to see those results. I really did expect the Pentax to perform better.

Pentax
Pentax smc FA 50 mm f/1.4 review - Image resolution - Lenstip.com

Sigma
Sigma 17-50 mm f/2.8 EX DC OS HSM review - Image resolution - Lenstip.com

12-15-2013, 08:05 AM   #2
Pentaxian
normhead's Avatar

Join Date: Jun 2007
Location: Near Algonquin Park
Photos: Gallery | Albums
Posts: 25,535
You need to try them out an see which results you like better. I wouldn't avoid using a zoom because it's a zoom, I don't have that particular bias, but I especially wouldn't pick a portrait lens based on resolution. Portrait lenses should be picked on rendition… in my day portrait lenses were intentionally a bit softer with better out of focus rendering.
12-15-2013, 08:31 AM   #3
Site Supporter
SpecialK's Avatar

Join Date: Dec 2006
Location: So California
Photos: Gallery
Posts: 14,848
Easy. You have the lenses - take sample shots and choose :-)

Why rely on a number, or us?
12-15-2013, 08:55 AM   #4
Veteran Member
maxfield_photo's Avatar

Join Date: Mar 2011
Location: Cincinnati, OH
Posts: 1,215
I find that sharpness is vastly overrated especially for portraiture. I'm not saying it's unimportant, but often times I end up softening the skin in post. What is important is the focus. You know that focus scale that's printed on most primes that shows the "zone of acceptable focus"? It's hogwash. In portraiture there is only the point of critical focus, everything else is out of focus. The point of critical focus needs to reside somewhere between the tips and the base of the eyelashes. Yeah, it's that small.

The Sigma may in fact be sharper that the Pentax 50, you have to remember that that lens is a decade old. You see the same thing from Canon and Nikon, some of their zooms out perform their primes, and 50mm in particular seems to be problematic. But I can almost guarantee that the 50mm Pentax will focus more accurately than the Sigma zoom. f/1.4 makes the difference between in focus and out of focus very apparent (particularly if you use a split prism focusing screen). Like others have said, since you own both lenses, try them out a see for yourself.

12-15-2013, 08:56 AM   #5
Veteran Member




Join Date: Oct 2011
Posts: 818
QuoteOriginally posted by normhead Quote
You need to try them out an see which results you like better. I wouldn't avoid using a zoom because it's a zoom, I don't have that particular bias, but I especially wouldn't pick a portrait lens based on resolution. Portrait lenses should be picked on rendition… in my day portrait lenses were intentionally a bit softer with better out of focus rendering.
Sonnars.... *ouch*!
12-15-2013, 09:15 AM   #6
Site Supporter
reivax's Avatar

Join Date: Jun 2011
Location: California
Posts: 736
Original Poster
I went ahead and performed the most unprofessional test I could think of and tested both lenses out at 2.8; 4; & 5.6. All images were taken with manual settings (to ensure everything was as identical as possible). All shots were handheld and ISO was set at 3200 (didn't want flash to alter colors, etc).

At 2.8, I think I like the Pentax more, after that, I think the Sigma renders colors a lot better than the Pentax.
Attached Images
View Picture EXIF
PENTAX K-30  Photo 
12-15-2013, 09:16 AM   #7
Site Supporter
reivax's Avatar

Join Date: Jun 2011
Location: California
Posts: 736
Original Poster
Do the colors look desaturated to anyone else? They shouldn't... Could photoshop have rendered them this way? On my computer, the images look fine. They colors are really off after uploading them to this site.
12-15-2013, 09:29 AM   #8
Pentaxian
normhead's Avatar

Join Date: Jun 2007
Location: Near Algonquin Park
Photos: Gallery | Albums
Posts: 25,535
The Pentax out of focus areas seem to be rendered about a stop ahead of the Sigma images, the Pentax @ ƒ4 looks closest to the Sigma @ f 2.8. Given that the Sigma is a slower lens… by 2 stops, that's a 3 stop disadvantage when looking at the out of focus areas. But I have no idea how important that is for you.


Last edited by normhead; 12-15-2013 at 09:35 AM.
12-15-2013, 09:34 AM   #9
Site Supporter
reivax's Avatar

Join Date: Jun 2011
Location: California
Posts: 736
Original Poster
It's got to be some setting in Photoshop that I don't know about. I exported the image through Lightroom and everything looks fine now... Any help with this would be greatly appreciated. Thanks. Here's the correct rendition.
Attached Images
 
12-15-2013, 09:36 AM   #10
Site Supporter
reivax's Avatar

Join Date: Jun 2011
Location: California
Posts: 736
Original Poster
QuoteOriginally posted by normhead Quote
The Pentax out of focus areas seem to rendered about a stop ahead of the Sigma images, the Pentax @ ƒ4 looks closest to the Sigma @ f 2.8. Given that the Sigma is a slower lens… by 2 stops, that's a 3 stop disadvantage when looking at the out of focus areas. But I have no idea how important that is for you.
Wow, I hadn't even noticed that. That is a pretty significant difference. And this is why I wanted your guys' opinions. Thanks. Anything else you notice?
12-15-2013, 10:21 AM   #11
Veteran Member




Join Date: Sep 2013
Posts: 306
Looks to me that in FA50 pics focus is more in front than sigma pics and this will explain most of different background blur ratio.

I believe that my FA50 gives better IQ than any of my zooms in 50mm...including also tamron 17-50,28-75...sigma 17-50 i do not own but i do believe FA50 will be better than any zooms in 50mm for pentax...but difference can be very little only.
12-15-2013, 11:32 AM   #12
Loyal Site Supporter
Canada_Rockies's Avatar

Join Date: Nov 2007
Location: Sparwood, BC, Canada
Photos: Gallery | Albums
Posts: 9,446
QuoteOriginally posted by reivax Quote
Wow, I hadn't even noticed that. That is a pretty significant difference. And this is why I wanted your guys' opinions. Thanks. Anything else you notice?
Given that the focus seems to be slightly different, if you have a body that allows focus adjustment, try adjusting the 50 to focus better. You can pay for super fancy gizmos, but a ruler at an angle should do the job.
12-15-2013, 12:09 PM   #13
Pentaxian
Na Horuk's Avatar

Join Date: Feb 2012
Location: Slovenia, probably
Photos: Gallery | Albums
Posts: 10,819
A reason for the odd colours might be the colour space setting, on your camera and in the software that you use to edit files. You probably want them all to be set to sRGB, its a standard that works well for sharing online.
Personally I prefer to use primes, and at f1.4 you can get a lot of background blur/subject isolation. Just make sure the person's eyes (or at least the one closest to the camera) is in perfect focus. Primes also kind of force you to frame more creatively. With zooms people often just stop in front of their subject and then zoom a little and take a shot. With a prime, you might be forced to take a step back or forward, and suddenly you will think about crouching a little or leaning to the side.. maybe its just me, though. Lots of people get great results from zoom lenses, I dont want to put anybody down.
12-15-2013, 12:19 PM   #14
Site Supporter
reivax's Avatar

Join Date: Jun 2011
Location: California
Posts: 736
Original Poster
QuoteOriginally posted by Canada_Rockies Quote
Given that the focus seems to be slightly different, if you have a body that allows focus adjustment, try adjusting the 50 to focus better. You can pay for super fancy gizmos, but a ruler at an angle should do the job.
I've never really had any issues with focusing on the FA 50. I didn't really pay too much attention to where I focused on the plant. I was more concerned with color rendition, but now I'm wishing I would have. I will definitely pay more attention to my focus points. Maybe I do need to adjust it.

Would that inch or two difference in focus point really make that much of a difference in how out of focus the background is? I know it does make a difference, but a full stop?
12-15-2013, 12:21 PM   #15
Site Supporter
reivax's Avatar

Join Date: Jun 2011
Location: California
Posts: 736
Original Poster
QuoteOriginally posted by Na Horuk Quote
A reason for the odd colours might be the colour space setting, on your camera and in the software that you use to edit files. You probably want them all to be set to sRGB, its a standard that works well for sharing online.
Personally I prefer to use primes, and at f1.4 you can get a lot of background blur/subject isolation. Just make sure the person's eyes (or at least the one closest to the camera) is in perfect focus. Primes also kind of force you to frame more creatively. With zooms people often just stop in front of their subject and then zoom a little and take a shot. With a prime, you might be forced to take a step back or forward, and suddenly you will think about crouching a little or leaning to the side.. maybe its just me, though. Lots of people get great results from zoom lenses, I dont want to put anybody down.
I use sRGB for everything. My editing programs are Lightroom 5 and Photoshop CS6. I've never had an issue like that with any other image I've edited on Photoshop, it seems to be this particular file only. I'll look into the settings to see if something got changed. Thanks.
Reply

Bookmarks
  • Submit Thread to Facebook Facebook
  • Submit Thread to Twitter Twitter
  • Submit Thread to Digg Digg
Tags - Make this thread easier to find by adding keywords to it!
fa, k-mount, mm, pentax, pentax fa, pentax lens, resolution, results, sigma, sigma 17-50 mm, slr lens, vs sigma
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
New Sigma 35mm f/1.4 vs. Pentax FA 31mm vs. Tamron 17-50mm f/2.8 tlwyse Pentax SLR Lens Discussion 35 07-29-2013 08:49 PM
For Sale - Sold: K-5, 16-50,50-135,65-250, Sigma 17-50, 50 1.4, 50 1.8, Tamron 90 2.8, Flashes virarfast Sold Items 8 04-04-2013 02:30 PM
For Sale - Sold: Sigma 50-150mm f/2.8 - $750 or trade for Sigma 85mm 1.4 or Sigma 17-50mm f/2.8 Edgar_in_Indy Sold Items 4 03-29-2013 09:10 PM
For Sale - Sold: Pentax K-7 w/ grip, FA 50mm f/1.4, DA 50-200, Tamron 17-50 f/2.8, Sigma flash Kazy Sold Items 8 11-11-2010 02:22 AM



All times are GMT -7. The time now is 07:56 AM. | See also: NikonForums.com, CanonForums.com part of our network of photo forums!
  • Red (Default)
  • Green
  • Gray
  • Dark
  • Dark Yellow
  • Dark Blue
  • Old Red
  • Old Green
  • Old Gray
  • Dial-Up Style
Hello! It's great to see you back on the forum! Have you considered joining the community?
register
Creating a FREE ACCOUNT takes under a minute, removes ads, and lets you post! [Dismiss]
Top