Pentax 50 DA 1.8 vs Manual Lenses

Pablom · 11-10-2014, 01:58 AM

Originally posted by axelm7

The M 1.7 gives you the equivalent field of view of an 80mm APS-C lens when being used in a Pentax DSLR as far as I know. Try shooting a subject from the same distance with the DA 50mm and with any film-era 50mm, and you'll see that the manual lenses seem to have a longer focal length.

I did that many times and I believe you did not.
I don't know how did you get to that assumption but it is 100% false.
mm is an absolute unit, not relative.

axelm7 · 11-10-2014, 02:00 AM

Originally posted by filoxophy

Focal length is a property of the lens, so any 50mm lens will have the same FOV when mounted on your Pentax DSLR (until they come out with 135 format sensor). The DA* 55mm f/1.4 will look the same through your viewfinder as the DFA 645 55mm f/2.8, if they're both mounted on a K-3, for example.

While you're correct about the focal length being a physical property of the lens, and thus an aspect that won't change no matter where it's mounted, a 55mm Porst 1.2 lens will give you a FOV equivalent to an 80mm lens designed for APS-C cameras, and if you managed to mount a 645 55mm 2.8 on a Pentax DSLR it would give you a FOV roughly equivalent to a 135mm lens designed for APS-C cameras.

The short and sweet version: focal length is a physical property and remains the same, which means that DOF stays the same. FOV does change when using a lens designed for a 35mm image circle on a crop-factor camera.

Yos · 11-10-2014, 02:09 AM

Well back to the topic.
As you can see in my signature I have a few of the lenses you are asking about and my recommendation would be to get a Pentax F(a) 50mm macro if your budget allows it. Damn fun to use a true macro as your walkaround lens and my DA 50 only get used if I know I will be shooting in dark environment.
Since I have the XS version of the 40mm I use it mainly as my travel lens to save up space but I find the lens very good and a good compromise between my 50's and my 35mm.
I think the only thing that stands in your way is your own budget as you will find a usage for an AF lens. As previous poster said, I also like the colour of the vintage glass but I prefer an AF nowadays. (Getting lazy....)

axelm7 · 11-10-2014, 02:40 AM

Originally posted by Pablom

I did that many times and I believe you did not.
I don't know how did you get to that assumption but it is 100% false.
mm is an absolute unit, not relative.

Are you sure we're on the same page? Focal length does not change. FOV does.

See my reply to filoxophy. In case that's not enough:

You Tube

Blog @ BorrowLenses

Full Frame vs Crop Frame Sensors | Everything You Need to Know

http://neilvn.com/tangents/full-frame-vs-crop-sensor-cameras-comparison-depth-of-field/

Crop Sensor (APS-C) Cameras and Lens Confusion

You're welcome.

**filoxophy** · 11-10-2014, 02:59 AM

Apparent FOV changes when you go between the same lens on different format bodies, not when different format (but same FL) lenses are mounted on the same body.

But yes, I will try to get back on topic too...

I like the DA50/1.8 a lot, especially for the price. For me, the only thing I'm losing over my manual 50s is build quality, distance/DOF markings, and an aperture ring for use with certain film bodies. As a plus, you get 7 rounded aperture blades.

The focus ring is actually really good IMHO, for a plastic AF lens. Much smoother and better damped than my DA35/2.4, with a longer travel as well. I don't use a hood since the front element is well recessed except at closest focus. Oh, one other downside--52mm filter threads! Haha, maybe that's just me. I just don't get why they went with 52mm when 49mm would fit with so many other Pentax primes. Oh and finally, no quickshift.

But like I said, it really is a great lens for the price IMHO. If you can swing the $170 or whatever and don't have film bodies that necessitate an aperture ring, I'd say go for it.

narual · 11-10-2014, 07:12 AM

Originally posted by Jannis

Thaks you all form your advices. I have one more question. I have also SMC 40 ldt... Do I need 50mm? Stupid question, I know... Is difference between 40 and 50 enought? Just now, my lenses and my k-5ii is in service for calibrating becouse AF issues , btw.

40mm focused at 10 feet wide open: 9.04 - 11.2 feet in focus.
32.61 horizontal degree angle of view at 10 feet is about a 5.8 foot wide slice at 10 feet.

50mm focused at 10 feet wide open: 9.59 - 10.4 feet in focus
26.34 horizontal degree angle of view at 10 feet is about a 4.7 foot wide slice at 10 feet

Tamron's focal length comparison tool isn't so useful for comparing normal-ish stuff since it's all basically landscape shots.

The CameraSim simulator might be a better way for you to do a direct comparison of the focal lengths, but its aperture setting only goes down to 2.8 so you won't get the same depth of field as with the 50mm.

(to save some time: Lighting overcast, distance 10 feet (or whatever you prefer), focal length 40/50 obviously, manual mode, with tripod, iso 100, aperture 2.8, shutter 1/40 does a good job of freezing the girl's movement while still capturing the movement of the pinwheel. (it's too bad there's no ND filter or faster aperture option. Probably is in the non-free version of the software)

**clackers** · 11-10-2014, 09:51 PM

Originally posted by axelm7

FOV does change when using a lens designed for a 35mm image circle on a crop-factor camera.

No, all the fifties have the same FoV.

What can vary is the vignetting.

schnitzer79 · 11-10-2014, 11:59 PM

i have the DA50 1.8 and the A-50 1.4. I do prefer having AF but most of the times I reach for the A-50 since I love how it renders and the bokeh is simply amazing. The DA is sharp around 2-2.4 and super sharp above 2.8. the only thing im not fond of in both lenses are the CA's when wide open. that can easily be fixed in PP though. If you dont mind shooting manual go for the M-50

axelm7 · 11-11-2014, 10:12 AM

Originally posted by clackers

No, all the fifties have the same FoV.

What can vary is the vignetting.

A common misconception about lenses. Please read any of the links I posted.

**clackers** · 11-11-2014, 01:04 PM

Originally posted by axelm7

A common misconception about lenses. Please read any of the links I posted.

With eyes rolling, I just read the Huff blog, to indulge you.

What was it meant to prove?

I say again, how does it show the M50 having a different FoV from the DA50?

narual · 11-11-2014, 01:14 PM

Originally posted by axelm7

A common misconception about lenses. Please read any of the links I posted.

Nonsense. my 50mm M lens and the 50mm end of my 50-135 frame identically on my k5.

If I took the two lenses on a film camera, they would show an identical framing (but the 50-135 might have really bad vignetting) to one another, but not the same framing as they do on the k5. If I stick a 1.5x teleconverter on the film camera, they match what you'd see on the K5.

**clackers** · 11-11-2014, 01:18 PM

Originally posted by narual

Nonsense. my 50mm M lens and the 50mm end of my 50-135 frame identically on my k5.

Yes, I don't know how he could try to get away posting that when there would always be readers who own both lenses.

Baffling.

It's advisable to only tell tall stories in a bar to an audience that can't contradict them!

Pablom · 11-11-2014, 01:23 PM

Originally posted by axelm7

A common misconception about lenses. Please read any of the links I posted.

Mr axelm7, with all due respect, I don't intend to repeat myself again and again.
Just as clackers, filoxophy and myself explained, all fifties do have the same FOV and none of your links disprove that.
You are being rude and, worse, misleading. Obviously you did not try for yourself what you so eagerly advocate whereas many of us, including myself did.
I do not claim things in the forums which I do not have personal experience with and when I do make an opinion I try to clarify what it is based on, specifically if writing about lenses it is only fair that to express a public opinion without trying to bias or mislead it must be based on personal experience. Obviously when there is no experience it should be disclosed.

**clackers** · 11-11-2014, 01:33 PM

Originally posted by Pablom

Obviously when there is no experience it should be disclosed.

Pablo, these equivalence/total light/frame size freaks scare me.

LensBeginner · 11-11-2014, 03:29 PM

Originally posted by clackers

I'm led to believe the 1.8 is optically the same as the 1.7, with a little loss of aperture happening in the plastic remounting (like the DA35/FA35).

I'm interested in this assertion.
Where did you read about it or what led you to believe this?

I've read on an "unspeakable" website that the f/1.7 is "almost as if this was optimized as an f/2 lens" and was oversized to f/1.7 only for marketing purposes, so it all looks plausible...
I can confirm this having tested myself, the horror of the corners at f/1.7, on APS-C... I just wonder what the corners must look like on film or FF... brrr...

11-10-2014, 02:00 AM	#17
axelm7 Forum Member Join Date: Dec 2013 Posts: 95	Originally posted by filoxophy Focal length is a property of the lens, so any 50mm lens will have the same FOV when mounted on your Pentax DSLR (until they come out with 135 format sensor). The DA* 55mm f/1.4 will look the same through your viewfinder as the DFA 645 55mm f/2.8, if they're both mounted on a K-3, for example. While you're correct about the focal length being a physical property of the lens, and thus an aspect that won't change no matter where it's mounted, a 55mm Porst 1.2 lens will give you a FOV equivalent to an 80mm lens designed for APS-C cameras, and if you managed to mount a 645 55mm 2.8 on a Pentax DSLR it would give you a FOV roughly equivalent to a 135mm lens designed for APS-C cameras. The short and sweet version: focal length is a physical property and remains the same, which means that DOF stays the same. FOV does change when using a lens designed for a 35mm image circle on a crop-factor camera. Last edited by axelm7; 11-10-2014 at 02:41 AM.

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Voigtlander color ultron 50/1.8 vs Pentax 50/1.7	yusuf	Pentax SLR Lens Discussion	6	05-01-2014 12:41 AM
Sigma 50/1.4 EX vs. Pentax FA 50/1.4 and DA 55/1.4	DonovanDwyer	Pentax SLR Lens Discussion	17	01-24-2014 12:54 PM
Sigma 18-35 f/1.8 vs the Pentax DA 16-50 f/2.8	someguy42	Pentax SLR Lens Discussion	9	12-06-2013 12:02 AM
F50 1.7 vs DA 50 1.8	Motyl	Pentax SLR Lens Discussion	10	10-03-2013 09:31 AM
50 A 1.2 vs 43 Limited vs 50 FA 1.4 vs DA* 55?	McLovin	Pentax SLR Lens Discussion	6	10-15-2009 09:17 PM

11-10-2014, 01:58 AM	#16
Pablom Veteran Member Join Date: Feb 2010 Location: Usa Posts: 1,940	Originally posted by axelm7 The M 1.7 gives you the equivalent field of view of an 80mm APS-C lens when being used in a Pentax DSLR as far as I know. Try shooting a subject from the same distance with the DA 50mm and with any film-era 50mm, and you'll see that the manual lenses seem to have a longer focal length. I did that many times and I believe you did not. I don't know how did you get to that assumption but it is 100% false. mm is an absolute unit, not relative.

11-10-2014, 02:09 AM	#18
Yos Veteran Member Join Date: Jan 2013 Location: Stockholm Photos: Gallery \| Albums Posts: 533	Well back to the topic. As you can see in my signature I have a few of the lenses you are asking about and my recommendation would be to get a Pentax F(a) 50mm macro if your budget allows it. Damn fun to use a true macro as your walkaround lens and my DA 50 only get used if I know I will be shooting in dark environment. Since I have the XS version of the 40mm I use it mainly as my travel lens to save up space but I find the lens very good and a good compromise between my 50's and my 35mm. I think the only thing that stands in your way is your own budget as you will find a usage for an AF lens. As previous poster said, I also like the colour of the vintage glass but I prefer an AF nowadays. (Getting lazy....)

11-10-2014, 02:59 AM	#20
filoxophy Site Supporter Join Date: Jul 2012 Location: Albuquerque Posts: 1,132	Apparent FOV changes when you go between the same lens on different format bodies, not when different format (but same FL) lenses are mounted on the same body. But yes, I will try to get back on topic too... I like the DA50/1.8 a lot, especially for the price. For me, the only thing I'm losing over my manual 50s is build quality, distance/DOF markings, and an aperture ring for use with certain film bodies. As a plus, you get 7 rounded aperture blades. The focus ring is actually really good IMHO, for a plastic AF lens. Much smoother and better damped than my DA35/2.4, with a longer travel as well. I don't use a hood since the front element is well recessed except at closest focus. Oh, one other downside--52mm filter threads! Haha, maybe that's just me. I just don't get why they went with 52mm when 49mm would fit with so many other Pentax primes. Oh and finally, no quickshift. But like I said, it really is a great lens for the price IMHO. If you can swing the $170 or whatever and don't have film bodies that necessitate an aperture ring, I'd say go for it.

11-10-2014, 07:12 AM	#21
narual Veteran Member Join Date: Jun 2013 Location: South Bend (Notre Dame), Indiana Photos: Gallery \| Albums Posts: 1,988	Originally posted by Jannis Thaks you all form your advices. I have one more question. I have also SMC 40 ldt... Do I need 50mm? Stupid question, I know... Is difference between 40 and 50 enought? Just now, my lenses and my k-5ii is in service for calibrating becouse AF issues , btw. 40mm focused at 10 feet wide open: 9.04 - 11.2 feet in focus. 32.61 horizontal degree angle of view at 10 feet is about a 5.8 foot wide slice at 10 feet. 50mm focused at 10 feet wide open: 9.59 - 10.4 feet in focus 26.34 horizontal degree angle of view at 10 feet is about a 4.7 foot wide slice at 10 feet Tamron's focal length comparison tool isn't so useful for comparing normal-ish stuff since it's all basically landscape shots. The CameraSim simulator might be a better way for you to do a direct comparison of the focal lengths, but its aperture setting only goes down to 2.8 so you won't get the same depth of field as with the 50mm. (to save some time: Lighting overcast, distance 10 feet (or whatever you prefer), focal length 40/50 obviously, manual mode, with tripod, iso 100, aperture 2.8, shutter 1/40 does a good job of freezing the girl's movement while still capturing the movement of the pinwheel. (it's too bad there's no ND filter or faster aperture option. Probably is in the non-free version of the software)

11-10-2014, 09:51 PM	#22
clackers Otis Memorial Pentaxian Join Date: Jul 2013 Location: Melbourne Photos: Albums Posts: 16,397	Originally posted by axelm7 FOV does change when using a lens designed for a 35mm image circle on a crop-factor camera. No, all the fifties have the same FoV. What can vary is the vignetting.

11-10-2014, 11:59 PM	#23
schnitzer79 Pentaxian Join Date: Jul 2013 Photos: Albums Posts: 1,248	i have the DA50 1.8 and the A-50 1.4. I do prefer having AF but most of the times I reach for the A-50 since I love how it renders and the bokeh is simply amazing. The DA is sharp around 2-2.4 and super sharp above 2.8. the only thing im not fond of in both lenses are the CA's when wide open. that can easily be fixed in PP though. If you dont mind shooting manual go for the M-50

11-11-2014, 10:12 AM	#24
axelm7 Forum Member Join Date: Dec 2013 Posts: 95	Originally posted by clackers No, all the fifties have the same FoV. What can vary is the vignetting. A common misconception about lenses. Please read any of the links I posted.

11-11-2014, 01:04 PM	#25
clackers Otis Memorial Pentaxian Join Date: Jul 2013 Location: Melbourne Photos: Albums Posts: 16,397	Originally posted by axelm7 A common misconception about lenses. Please read any of the links I posted. With eyes rolling, I just read the Huff blog, to indulge you. What was it meant to prove? I say again, how does it show the M50 having a different FoV from the DA50?

11-11-2014, 01:14 PM	#26
narual Veteran Member Join Date: Jun 2013 Location: South Bend (Notre Dame), Indiana Photos: Gallery \| Albums Posts: 1,988	Originally posted by axelm7 A common misconception about lenses. Please read any of the links I posted. Nonsense. my 50mm M lens and the 50mm end of my 50-135 frame identically on my k5. If I took the two lenses on a film camera, they would show an identical framing (but the 50-135 might have really bad vignetting) to one another, but not the same framing as they do on the k5. If I stick a 1.5x teleconverter on the film camera, they match what you'd see on the K5.

11-11-2014, 01:18 PM	#27
clackers Otis Memorial Pentaxian Join Date: Jul 2013 Location: Melbourne Photos: Albums Posts: 16,397	Originally posted by narual Nonsense. my 50mm M lens and the 50mm end of my 50-135 frame identically on my k5. Yes, I don't know how he could try to get away posting that when there would always be readers who own both lenses. Baffling. It's advisable to only tell tall stories in a bar to an audience that can't contradict them!

11-11-2014, 01:23 PM	#28
Pablom Veteran Member Join Date: Feb 2010 Location: Usa Posts: 1,940	Originally posted by axelm7 A common misconception about lenses. Please read any of the links I posted. Mr axelm7, with all due respect, I don't intend to repeat myself again and again. Just as clackers, filoxophy and myself explained, all fifties do have the same FOV and none of your links disprove that. You are being rude and, worse, misleading. Obviously you did not try for yourself what you so eagerly advocate whereas many of us, including myself did. I do not claim things in the forums which I do not have personal experience with and when I do make an opinion I try to clarify what it is based on, specifically if writing about lenses it is only fair that to express a public opinion without trying to bias or mislead it must be based on personal experience. Obviously when there is no experience it should be disclosed.

11-11-2014, 01:33 PM	#29
clackers Otis Memorial Pentaxian Join Date: Jul 2013 Location: Melbourne Photos: Albums Posts: 16,397	Originally posted by Pablom Obviously when there is no experience it should be disclosed. Pablo, these equivalence/total light/frame size freaks scare me.

11-11-2014, 03:29 PM	#30
LensBeginner Veteran Member Join Date: Sep 2014 Photos: Albums Posts: 4,696	Originally posted by clackers I'm led to believe the 1.8 is optically the same as the 1.7, with a little loss of aperture happening in the plastic remounting (like the DA35/FA35). I'm interested in this assertion. Where did you read about it or what led you to believe this? I've read on an "unspeakable" website that the f/1.7 is "almost as if this was optimized as an f/2 lens" and was oversized to f/1.7 only for marketing purposes, so it all looks plausible... I can confirm this having tested myself, the horror of the corners at f/1.7, on APS-C... I just wonder what the corners must look like on film or FF... brrr...