Pentax 31/1.8 Limited vs Sony 35/1.4 GM

**akptc** · 05-03-2022, 02:55 PM

This a bit of an odd dilemma. I have the Pentax 31/1.8 limited and it is nice and sharp on my full frame Sony body. The AF with the Monster adapter is not bad. Then there is the Sony 35/1.4 GM lens, which I understand has excellent IQ and decent AF. So I am trying to decide if I want to buy the Sony lens. I played with it today at a store and it handles well. Plus it is a bit faster. One possible issue with the Pentax 31mm is that, even though it's sharp on my K3 and on the Sony FE bodies, I am having a difficult time fine tuning it (focus) on the Pentax K3-III. Of course that might just be me.

Has anyone here had a chance to shoot with both of them and form an opinion?

____________
By the way, the main reason I want a good +/35mm lens for the Sony is that I like the 35/85 combo (or 28/85 combo), especially if the total weight is low.

Last edited by akptc; 05-04-2022 at 05:13 PM.

**UncleVanya** · 05-03-2022, 05:34 PM

I haven’t. But I do have the 31 and an a7R III and the monster adapter. I like that combo. To me the 31 offers almost 28mm which I like better than 35mm.

zapp · 05-04-2022, 12:15 PM

The 31 is a fullframe retro focus design with loud AF. Angle of view matches a ff 50 mm, but with all the retro focus drawbacks. Image drawing and 3d drawing are great. I don’t like it too much on apsc = K3x. On a Sony FF it draws nicely, but the 35 is native Sony mount. If you like size and performance of the 35, it makes most sense on ff. Going across brands and across sensor formats makes thus a tricky decision… get both, play around with both and decide later which one to keep.

**akptc** · 05-04-2022, 05:08 PM

Originally posted by UncleVanya

the 31 offers almost 28mm

Good point. I see a "3" and immediately think 35mm..

---------- Post added 05-04-22 at 17:10 ----------

Originally posted by zapp

play around with both and decide later which one to keep.

Thanks! I was waiting for another voice (other than the one in my head) to say this would be a god idea

**UncleVanya** · 05-04-2022, 07:13 PM

Originally posted by akptc

Good point. I see a "3" and immediately think 35mm..

Good 35's are a dime a dozen in Sony land - 28's not so much. 31 - not at all really. The size and weight of the 31 is spectacular but you add the monster adapter and lose some of that advantage. The 31 has a really good character and it is surprisingly sharp compared to what I think people expect of a film era lens. It is not however a 35 and not a 1.4 and doesn't have built in distortion profiles on the Sony. So it depends greatly on what you want from the lenses. If you want razor sharp - the 35 GM is probably the one to grab. Nearly as sharp with some character - 31. Wider but not too wide; 31 again. Faster tracking - 35 GM. Fun factor - ? Depends on you.

Winder · 05-13-2022, 08:10 PM

I have used both and currently have the Sony/Zeiss 35mm F/1.4. The 31mm LTD was one of my favorite lenses on my K-3. It was fine on my K-1 and I used it on my Sony A7II for a couple of years before selling it. I don't know which Sony body you are using, but on anything newer than the A7II AF will be greatly improved. The 35mm GM is a great lens and I have tried it out several times, but never bought. The Sigma and the Sony Zeiss are also great options. The modern mirrorless AF is simply amazing. The only reason I would keep the 31mm is for size.

**akptc** · 05-15-2022, 04:57 PM

After more research, I am getting the 35/1.4 GM and will probably sell the 31/1.8. I also just discovered the yummy 50/1.2 GM, which throws a bit of a kink into my plans to stick to a 2 lens kit (7R4 + 35/1.4 + 85/1.8)

**BruceBanner** · 05-20-2022, 03:19 AM

Originally posted by akptc

This a bit of an odd dilemma. I have the Pentax 31/1.8 limited and it is nice and sharp on my full frame Sony body. The AF with the Monster adapter is not bad. Then there is the Sony 35/1.4 GM lens, which I understand has excellent IQ and decent AF. So I am trying to decide if I want to buy the Sony lens. I played with it today at a store and it handles well. Plus it is a bit faster. One possible issue with the Pentax 31mm is that, even though it's sharp on my K3 and on the Sony FE bodies, I am having a difficult time fine tuning it (focus) on the Pentax K3-III. Of course that might just be me.

Has anyone here had a chance to shoot with both of them and form an opinion?

____________
By the way, the main reason I want a good +/35mm lens for the Sony is that I like the 35/85 combo (or 28/85 combo), especially if the total weight is low.

You're not the only one. There is something very peculiar going on with all three FA Ltds on the K3III vs other Pentax bodies. The green hex (what it considers to be in and out of focus) has an outrageous scope, it's massive leading to very erratic results and soft shots. I've talked and explained about this in depth elsewhere.

Sandy Hancock · 05-20-2022, 03:57 AM

I have a private theory, which I have not formally tested (because I'm lazy and don't make a living out of photography), that the top edge of the active AF point (rather than the centre) should be pointed at the target. My experience is mainly with the K-1 though - I haven't used my FA Limiteds on the K-3 Mark III yet....

Give it a whirl and see how you go.

**UncleVanya** · 05-20-2022, 05:34 AM

Originally posted by Sandy Hancock

I have a private theory, which I have not formally tested (because I'm lazy and don't make a living out of photography), that the top edge of the active AF point (rather than the centre) should be pointed at the target. My experience is mainly with the K-1 though - I haven't used my FA Limiteds on the K-3 Mark III yet....

Give it a whirl and see how you go.

How do you know where the edge is? The focus point indicators are not precisely the same size and shape as the actual focus points are they?

Sandy Hancock · 05-20-2022, 05:56 AM - **1 Like**

Originally posted by UncleVanya

The focus point indicators are not precisely the same size and shape as the actual focus points are they?

Indeed they are not, which is exactly my point.

I'm just saying that I have had more luck using the top edge of the focus point indicators. Others' mileage may vary.

**UncleVanya** · 05-20-2022, 04:00 PM

Originally posted by Sandy Hancock

Indeed they are not, which is exactly my point.

I'm just saying that I have had more luck using the top edge of the focus point indicators. Others' mileage may vary.

Useful. I wasn’t sure if this was more complicated than just putting the indicator in that position. Thanks Sandy.

**akptc** · 05-20-2022, 07:56 PM

Originally posted by BruceBanner

leading to very erratic results and soft shots.

It's good to know it wasn't just my bad luck again...

---------- Post added 05-20-22 at 19:57 ----------

Originally posted by Sandy Hancock

more luck using the top edge of the focus point indicators.

Thanks for the tip!

05-03-2022, 02:55 PM	#1
akptc Site Supporter Join Date: Feb 2008 Location: USA Photos: Gallery Posts: 771	Pentax 31/1.8 Limited vs Sony 35/1.4 GM This a bit of an odd dilemma. I have the Pentax 31/1.8 limited and it is nice and sharp on my full frame Sony body. The AF with the Monster adapter is not bad. Then there is the Sony 35/1.4 GM lens, which I understand has excellent IQ and decent AF. So I am trying to decide if I want to buy the Sony lens. I played with it today at a store and it handles well. Plus it is a bit faster. One possible issue with the Pentax 31mm is that, even though it's sharp on my K3 and on the Sony FE bodies, I am having a difficult time fine tuning it (focus) on the Pentax K3-III. Of course that might just be me. Has anyone here had a chance to shoot with both of them and form an opinion? ____________ By the way, the main reason I want a good +/35mm lens for the Sony is that I like the 35/85 combo (or 28/85 combo), especially if the total weight is low. Last edited by akptc; 05-04-2022 at 05:13 PM.

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05-03-2022, 05:34 PM	#2
UncleVanya Loyal Site Supporter Join Date: Jul 2014 Photos: Gallery \| Albums Posts: 28,401	I haven’t. But I do have the 31 and an a7R III and the monster adapter. I like that combo. To me the 31 offers almost 28mm which I like better than 35mm.

05-04-2022, 12:15 PM	#3
zapp Pentaxian Join Date: Jul 2011 Posts: 2,385	The 31 is a fullframe retro focus design with loud AF. Angle of view matches a ff 50 mm, but with all the retro focus drawbacks. Image drawing and 3d drawing are great. I don’t like it too much on apsc = K3x. On a Sony FF it draws nicely, but the 35 is native Sony mount. If you like size and performance of the 35, it makes most sense on ff. Going across brands and across sensor formats makes thus a tricky decision… get both, play around with both and decide later which one to keep.

05-04-2022, 05:08 PM	#4
akptc Site Supporter Join Date: Feb 2008 Location: USA Photos: Gallery Posts: 771 Original Poster	Originally posted by UncleVanya the 31 offers almost 28mm Good point. I see a "3" and immediately think 35mm.. ---------- Post added 05-04-22 at 17:10 ---------- Originally posted by zapp play around with both and decide later which one to keep. Thanks! I was waiting for another voice (other than the one in my head) to say this would be a god idea

05-04-2022, 07:13 PM	#5
UncleVanya Loyal Site Supporter Join Date: Jul 2014 Photos: Gallery \| Albums Posts: 28,401	Originally posted by akptc Good point. I see a "3" and immediately think 35mm.. Good 35's are a dime a dozen in Sony land - 28's not so much. 31 - not at all really. The size and weight of the 31 is spectacular but you add the monster adapter and lose some of that advantage. The 31 has a really good character and it is surprisingly sharp compared to what I think people expect of a film era lens. It is not however a 35 and not a 1.4 and doesn't have built in distortion profiles on the Sony. So it depends greatly on what you want from the lenses. If you want razor sharp - the 35 GM is probably the one to grab. Nearly as sharp with some character - 31. Wider but not too wide; 31 again. Faster tracking - 35 GM. Fun factor - ? Depends on you.

05-13-2022, 08:10 PM	#6
Winder Veteran Member Join Date: Apr 2010 Location: Tennessee Posts: 6,617	I have used both and currently have the Sony/Zeiss 35mm F/1.4. The 31mm LTD was one of my favorite lenses on my K-3. It was fine on my K-1 and I used it on my Sony A7II for a couple of years before selling it. I don't know which Sony body you are using, but on anything newer than the A7II AF will be greatly improved. The 35mm GM is a great lens and I have tried it out several times, but never bought. The Sigma and the Sony Zeiss are also great options. The modern mirrorless AF is simply amazing. The only reason I would keep the 31mm is for size.

05-15-2022, 04:57 PM	#7
akptc Site Supporter Join Date: Feb 2008 Location: USA Photos: Gallery Posts: 771 Original Poster	After more research, I am getting the 35/1.4 GM and will probably sell the 31/1.8. I also just discovered the yummy 50/1.2 GM, which throws a bit of a kink into my plans to stick to a 2 lens kit (7R4 + 35/1.4 + 85/1.8)

05-20-2022, 03:19 AM	#8
BruceBanner Site Supporter Join Date: Dec 2015 Posts: 5,404	Originally posted by akptc This a bit of an odd dilemma. I have the Pentax 31/1.8 limited and it is nice and sharp on my full frame Sony body. The AF with the Monster adapter is not bad. Then there is the Sony 35/1.4 GM lens, which I understand has excellent IQ and decent AF. So I am trying to decide if I want to buy the Sony lens. I played with it today at a store and it handles well. Plus it is a bit faster. One possible issue with the Pentax 31mm is that, even though it's sharp on my K3 and on the Sony FE bodies, I am having a difficult time fine tuning it (focus) on the Pentax K3-III. Of course that might just be me. Has anyone here had a chance to shoot with both of them and form an opinion? ____________ By the way, the main reason I want a good +/35mm lens for the Sony is that I like the 35/85 combo (or 28/85 combo), especially if the total weight is low. You're not the only one. There is something very peculiar going on with all three FA Ltds on the K3III vs other Pentax bodies. The green hex (what it considers to be in and out of focus) has an outrageous scope, it's massive leading to very erratic results and soft shots. I've talked and explained about this in depth elsewhere.

05-20-2022, 03:57 AM	#9
Sandy Hancock Moderator Site Supporter Join Date: Feb 2012 Location: Adelaide Hills, South Australia Photos: Gallery \| Albums Posts: 11,272	I have a private theory, which I have not formally tested (because I'm lazy and don't make a living out of photography), that the top edge of the active AF point (rather than the centre) should be pointed at the target. My experience is mainly with the K-1 though - I haven't used my FA Limiteds on the K-3 Mark III yet.... Give it a whirl and see how you go.

05-20-2022, 05:34 AM	#10
UncleVanya Loyal Site Supporter Join Date: Jul 2014 Photos: Gallery \| Albums Posts: 28,401	Originally posted by Sandy Hancock I have a private theory, which I have not formally tested (because I'm lazy and don't make a living out of photography), that the top edge of the active AF point (rather than the centre) should be pointed at the target. My experience is mainly with the K-1 though - I haven't used my FA Limiteds on the K-3 Mark III yet.... Give it a whirl and see how you go. How do you know where the edge is? The focus point indicators are not precisely the same size and shape as the actual focus points are they?

05-20-2022, 05:56 AM - 1 Like	#11
Sandy Hancock Moderator Site Supporter Join Date: Feb 2012 Location: Adelaide Hills, South Australia Photos: Gallery \| Albums Posts: 11,272	Originally posted by UncleVanya The focus point indicators are not precisely the same size and shape as the actual focus points are they? Indeed they are not, which is exactly my point. I'm just saying that I have had more luck using the top edge of the focus point indicators. Others' mileage may vary.

05-20-2022, 04:00 PM	#12
UncleVanya Loyal Site Supporter Join Date: Jul 2014 Photos: Gallery \| Albums Posts: 28,401	Originally posted by Sandy Hancock Indeed they are not, which is exactly my point. I'm just saying that I have had more luck using the top edge of the focus point indicators. Others' mileage may vary. Useful. I wasn’t sure if this was more complicated than just putting the indicator in that position. Thanks Sandy.

05-20-2022, 07:56 PM	#13
akptc Site Supporter Join Date: Feb 2008 Location: USA Photos: Gallery Posts: 771 Original Poster	Originally posted by BruceBanner leading to very erratic results and soft shots. It's good to know it wasn't just my bad luck again... ---------- Post added 05-20-22 at 19:57 ---------- Originally posted by Sandy Hancock more luck using the top edge of the focus point indicators. Thanks for the tip!