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01-06-2014, 01:44 PM   #1
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Best 28-25mm prime for my new K3?

Hello Everybody!
Guys, one favour, I'm undecided about my 35mm prime lens choice, I was reading the lenses section and doing my on-line research so more or less I know what are the options available but I'm not sure which lens to pick up If I already have a DA 50mm 1.4 (that i mainly use indoors for portraits)

My gear:
Sigma 10-20 ( Architecture and very wide shots)
DA 50mm 1.4 (indoors portraits and close ups)
Sigma 17-70mm f/2.8-4.5 DC Macro (Walk around piece / fair enough but would like to upgrade later on)
DA 50-200mm F4-5.6 (Standar zoom that works fine for my zoom portraits)

Dilemma:
Since I already have the DA 50mm 1.4 I dont see it as a walk around lens for street shots so I want a 35mm prime for my K3 and K5.
I'm wondering if some one can tell me if the :Pentax 35mm F2 PFA SMC AL on my K3 will look almost the same as my 50mm 1.4? (since is a Full Frame lens), If that is the case I wont buy it. I want a longer angle (I must say that I could get the 35mm 2.0 AL for almost 230 pounds)

My other alternatives are: (the criteria is 28-35mm and F/2.4 or faster)
Sigma 28 f1.8
Pentax DA 35 2.4
Sigma 30mm 1.4
Samyang 35mm (Manual)

Other suggestions? (Budget max 350 pounds)

Thanks for your suggestions and comments!

01-06-2014, 01:48 PM   #2
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QuoteOriginally posted by storytelling Quote
I'm wondering if some one can tell me if the :Pentax 35mm F2 PFA SMC AL on my K3 will look almost the same as my 50mm 1.4?
A 35mm is a lot wider than a 50mm. On APS-C a 35mm gives you 38 degrees horizontal field of view, while a 50mm lens only gives you 27.

35mm still isn't wide-angle, though, so I'd recommend looking at either of the Sigmas that you have listed.

Adam
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01-06-2014, 01:53 PM   #3
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I have the old Sigma 24mm Super Wide II Macro and it's great. Should be a review on here as well as sample pics.

Last edited by klkitchens; 01-06-2014 at 05:50 PM. Reason: Wrong darn focal length!
01-06-2014, 01:56 PM   #4
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FWIW, The Samyang 24mm f/1.4 ED AS UMC Wide-Angle Lens for Pentax SY24M-P Will do 57.6 when used with an APS-C.

01-06-2014, 01:58 PM   #5
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Sorry guys I made a mistyping mistake on the title . It should be : Best 28-35mm prime for my new K3? (but i guess you got the point :-) Cheers
01-06-2014, 02:01 PM   #6
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QuoteOriginally posted by storytelling Quote
I want a 35mm prime for my K3 and K5.
I'm wondering if some one can tell me if the :Pentax 35mm F2 PFA SMC AL on my K3 will look almost the same as my 50mm 1.4? (since is a Full Frame lens), If that is the case I wont buy it. I want a longer angle (I must say that I could get the 35mm 2.0 AL for almost 230 pounds)
The FA 35 will give a 45 degree diagonal view on the K3,
while your DA 50 only gives you about 30 degrees.
01-06-2014, 02:05 PM   #7
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QuoteOriginally posted by storytelling Quote
Hello Everybody!
I'm wondering if some one can tell me if the :Pentax 35mm F2 PFA SMC AL on my K3 will look almost the same as my 50mm 1.4? (since is a Full Frame lens)
The focal length is a physical feature of the lens and is independent of whether the lens will be mounted on a film/FF or APS-C camera. You don't need to convert anything--a lens that is 50mm that was made 40 years ago will give the same field of view as a 50mm lens that was made yesterday. It's a bit confusing because people talk about "equivalent focal length" and whatnot. Ignore all of it. It's meant for people who are used to film cameras and want a comparison they will understand.

The "FF compatible" lens part involves the back of the lens, the "image circle." A FF compatible lens has a circle that is wide enough to contain the 35mm sensors, while an APS-C only lens has a image circle only wide enough for the smaller APS-C sensor. In Pentax lingo, APS-C lenses are denoted DA while FA/FA* are used for FF compatible lenses. This is a bit of a misnomer, as some DA lenses are FF compatible, but it's model by model. Anything designated FA, however, is.

This image shows a manual film lens (left) with a Sigma lens compatible only with APS-C cameras (right). The image circles are highlighted in red. Notice how much smaller the Sigma's is?
IMG_1009.jpg

Last edited by MadMathMind; 10-09-2014 at 09:44 PM.
01-06-2014, 02:16 PM   #8
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Guys thank you all for your answers and explanation. Taking note of everything before taking a decision.

01-06-2014, 02:27 PM   #9
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To say a 50mm lens is still a 50mm lens if it's on a 1.5 crop Pentax sensor is strictly true but is not very helpful.
Equivalent field of view (FOV) is what most people want to know.

A 75mm on FF (35mm film) is equivalent to a 50mm (i.e., 1.5x50=75) in field of view on a Pentax dlsr

A 50mm on FF//is equivalent to about 35mm in field of view on a Pentax dlsr

A 40mm on FF//is is equivalent to about a 28mm in field of view on a Pentax dlsr

A 35mm on FF//is is equivalent to about a 24mm in field of view on a Pentax dlsr

For me a 28mm lens on my Pentax dslr is a good walk around lens. Somewhere between a 35 and 28mm (on Pentax dslr) would be traditional, but many find a 24mm (which is a about a 35mm lens FOV on FF) to be better for general use.

Last edited by dms; 01-06-2014 at 03:15 PM. Reason: Had my examples backwards
01-06-2014, 02:35 PM   #10
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As stated, a 35mm lens is 35mm regardless of camera (full frame, film, crop sensor), but a cropped sensor cuts off edges of the Field of View.
The FA 35mm (or DA 35mm or any other 35mm lens) will be significantly wider than the DA 50mm (or FA 50mm or any other 50mm lens). A lens being "full frame" only means it projects a big image circle, which is useless on a crop sensor camera.
That being said, the DA 35mm f2.4 is a great lens that doesn't cost too much. But! I wouldn't consider it to be really wide angle on crop sensor cameras, even though it is much wider than a 50mm. For landscapes and such, I usually want wider. The DA 35mm f2.8 ltd macro is apparently an even better lens and it allows macro with true 1:1 magnification at minimum focus distance. And it recently got an "HD coatings" upgrade. Some say its one of the best Pentax DA lenses. And then there is the FA 35mm f2.0, which is brighter and well liked, too. I don't think any of these lenses will really disappoint you, but there are differences between them.
Lots of people love the Sigma 30mm (if you dont mind the triangular bokeh).
01-06-2014, 02:55 PM - 1 Like   #11
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QuoteOriginally posted by MadMathMind Quote

The "FF compatible" lens part involves the back of the lens, the "image circle." A FF compatible lens has a circle that is wide enough to contain the 35mm sensors, while an APS-C only lens has a image circle only wide enough for the smaller APS-C sensor. In Pentax lingo, APS-C lenses are denoted DA while FA/FA* are used for FF compatible lenses. This is a bit of a misnomer, as some DA lenses are FF compatible, but it's model by model. Anything designated FA, however, is.

This image shows a manual film lens (left) with a Sigma lens compatible only with APS-C cameras (right). The image circles are highlighted in red. Notice how much smaller the Sigma's is?
IMG_1009.jpg
The diameter of the exit pupil (/lens) is not the same as the image circle !

Image circle is the circular picture the lens is forming on the plane of the sensor.

My fa 28 mm lens have a much smaller lens at the back compared with my fa 50 mm, and still is a full frame lens. (Though light rays will fall at a greater angle onto the sides of the sensor)

Lars
01-06-2014, 02:57 PM   #12
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Short answer, no a 35 will not look like the same FOV as a 50 on you camera. A 35mm on an APS-c will look like a 50 on a full-frame camera, but that is not relevant to you. Focal length is focal length. Within a small variation, any 50mm will give you the same field of view on you K-5. FF vs crop really only affect the image circle, which is why it's often called "equivalent".

If cost is a concern, and you want sharp corners, buy the DA35/2.4. If you want the center really really sharp, and can tolerate poor borders, the Sigma 30/1.4 is a champion. IMO, border performance is highly overrated. I have NEVER ONCE taken a shot with my Sigma that I felt was let down by terrible border sharpness.

If money is no object, then the FA31 or Sigma 35/1.4 are your lenses. Then again, I think the Sigma 30 is better for center sharpness than even these mighty lenses.

Buy used, here on the marketplace, sell it if you don't like it.
01-06-2014, 04:08 PM   #13
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Like you, there was this gap between my Sigma 10-20, DA50 1.8 and DA 55-300, but I'm happy now.

I've found the Sigma 24mm f1.8 to be a great walkaround lens.
01-06-2014, 05:38 PM - 1 Like   #14
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The easiest thing to do is to put your current Sigma 17-70mm f/2.8-4.5 DC Macro on the camera body then
  1. Turn the barrel to the 50mm use the viewfinder to center on something in particular, take a picture.
  2. Turn the barrel to the 35mm use the viewfinder to center on the exact same object and take another picture.
Now, you have an image of the 50mm and the 35mm views and you can make an informed decision.

01-06-2014, 05:50 PM - 1 Like   #15
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QuoteOriginally posted by klkitchens Quote
I have the old Sigma 24mm Super Wide II Macro and it's great. Should be a review on here as well as sample pics.

Sigma 24mm F2.8 AF Super Wide II Lens Reviews - Sigma Lenses - Pentax Lens Review Database
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