Photozone re-reviews FA31mm

**Rondec** · 05-18-2012, 04:49 PM

Originally posted by VisualDarkness

The (most often) higher pixel density of APS-C can lower the resolution score compared to FF and considering the pretty good border score here the 31mm could get really nice result if tested on a bigger sensor.

I guess. Its just that the extreme edge on APS-C is no where near the extreme edge on full frame. So, on a D800 (same pixel density as K5), you are going to see some border weakness. On D700, probably looks pretty strong.

VisualDarkness · 05-18-2012, 04:53 PM

Originally posted by Rondec

I guess. Its just that the extreme edge on APS-C is no where near the extreme edge on full frame. So, on a D800 (same pixel density as K5), you are going to see some border weakness. On D700, probably looks pretty strong.

But if the 31mm got good resolution at the extreme borders and that pixel density is less it could potentially get even greater result in the tests (vignetting will be bad though). This is of coarse nt as true for monsters like the D800.

liukaitc · 05-18-2012, 05:57 PM

same with kit lens they tested
the border and corner is worse on k5

Class A · 05-18-2012, 06:33 PM

It all makes sense because this time it was the "31mm f/1.8 Limied", i.e., not the "Limited" lens that was tested (see the title above the MTF figures).

Joking aside, I'm puzzled by the new figures. A peak at f/2.8, if true, would be extraordinary, but yet resolution figures are lower than that of the 35/2.4. This should only be possible if the 31/1.8 has relatively large aberrations that do not depend on the f-ratio. However, lateral CA seems well controlled. So what is the source (if all the figures are right)?

Does anyone know of any other MTF measurements for the FA 31/1.8?

Anyhow, the above is just measurebating (and of some interest to those with a curiosity for optics). I feel a 4/5 rating for the optical quality of the FA 31/1.8 is inadequate. What would a Stradivari receive at ~~photo~~audiozone.de? A 3.5 out of 5 for sound? I'm sure it has technical "flaws" and that these are part and parcel of what makes it special.

Last edited by Class A; 05-18-2012 at 06:42 PM.

vrrattko · 05-19-2012, 03:17 AM

Originally posted by Class A

Does anyone know of any other MTF measurements for the FA 31/1.8?

Well FA31 was also tested by Lenstip on K-5.....but they dismissed the lens as nothing special and overly expensive. That review pretty much trashed the aura of FA31.

Class A · 05-19-2012, 05:16 PM

Originally posted by vrrattko

Well FA31 was also tested by Lenstip on K-5.....

Thanks for the pointer.

According to their measurements the centre does definitely not peak at f/2.8, just like it did not with Photozone's earlier measurements. What is going on?

bossa · 05-19-2012, 05:24 PM

All I know is my 31 is razor sharp at all F ratios on my K-5 and that's good enough for me. I can't imagine selling that lens at all.

lytrytyr · 05-19-2012, 05:34 PM

Originally posted by Class A

I feel a 4/5 rating for the optical quality of the FA 31/1.8 is inadequate.

See Photozone Rating System

jsherman999 · 05-19-2012, 05:39 PM

Originally posted by Class A

Thanks for the pointer.

According to their measurements the centre does definitely not peak at f/2.8, just like it did not with Photozone's earlier measurements. What is going on?

Some type of sample variation? Is the newly tested sample MIJ or MIV?

Laurentiu Cristofor · 05-19-2012, 11:25 PM

The FA 31 is one of the best lenses that Pentax produced and can stand up next to lenses produced by anyone.

Lens reviews are interesting up to a point. I check them just to find out about major issues that I care about.

dankoBanana · 05-20-2012, 04:49 AM

Some people seem to discover the fact that sensors do play a role in the camera output just as much as a lens. The fact is, the 31 & 43 Limiteds are designed for film and are getting hammered on a 16MP sensor by DA Limited lenses designed for digital (DA 35 & DA 40). I expect the same will go for the FA 77 on a K5. The DA 70mm will best it on edge performance.

bossa · 05-20-2012, 04:59 AM - **1 Like**

--I find it hard to believe that my FA31 and FA77 are getting hammered (at the pub?

) by anything frankly. I am stunned every time I see my 31ltd shots after transferring them from the camera. It's easily the best lens I have used.
Just another mediocre image with BS edge sharpness etc etc:

And another one

What a crap lens it is... maybe I'll just give it away.

zapp · 05-20-2012, 05:08 AM

Originally posted by vrrattko

Well FA31 was also tested by Lenstip on K-5.....but they dismissed the lens as nothing special and overly expensive. That review pretty much trashed the aura of FA31.

Come it, the FA31 is a nice lens ... in a full format system with AF engine from the late 80's. On an APS-C camera it is a big dinosaur. I like mine, but I also know the problems. The photozone&lenstip reviews explains all the little problems - still prainsing the lens. This thread here only shows how narrow minded the Pentax community is regarding this lens. I only keep my 31FA because I have have use for it and it would be useful on a future full frame camera as wide angle lens - it was designed as a wide angle lens not a normal equiv. lens.
The 9.x rating in Pentax review does not count much in real world - almost everything is rated close to 9 or 10.

Class A · 05-20-2012, 05:25 AM

Originally posted by jsherman999

Some type of sample variation?

Even a decentred copy should have good centre performance (unless it is totally out of whack). Unless the lens is essentially damaged, the peak of sharpness should not shift (that much).

Maybe Klaus changed some measurement parameters but he seems puzzled by the changed measurements for the 43/1.9 as well so I don't necessarily expect him to have an answer.

Originally posted by dankoBanana

The fact is, the 31 & 43 Limiteds are designed for film and are getting hammered on a 16MP sensor by DA Limited lenses designed for digital (DA 35 & DA 40).

The FA Ltds and the DA Ltds have different optical designs. The FA Ltds have better peak performance but are not as consistent across the f-ratio range (A characteristic I prefer because I'm a) interested in peak sharpness and b) prefer the rendering of the FA designs.

Even if it were true that the FA Ltds were outdated, it would not explain a shift of peak performance of the 31/1.9 in a retest. It would not explain a drop in border performance of the 43/1.9 either. Something is going on with the photozone retests and Klaus does not appear to have the answers himself.

Class A · 05-20-2012, 05:33 AM

Originally posted by lytrytyr

See Photozone Rating System

I'm familiar with the PZ rating system and fully support avoiding inflation with ratings.

However, if lenses like the FA 31/1.8 receive 4/5 then one wonders what lenses will get a rating closer to 5. Maybe a boring macro lens?

Summary ratings are always problematic, but I do not think that degrading the FA 31/1.8's rating from 4.5/5 to 4/5 makes sense, if one considers the reputation of the lens with experienced photographers.

Maybe other lenses I do not know of have surpassed the 31/1.8 and are more deserving of a 4.5/5 or even 5/5.

05-18-2012, 05:57 PM	#18
liukaitc Veteran Member Join Date: Jul 2010 Location: New York Photos: Albums Posts: 1,008	same with kit lens they tested the border and corner is worse on k5 Last edited by liukaitc; 05-19-2012 at 07:02 PM.

05-20-2012, 04:59 AM - 1 Like	#27
bossa Veteran Member Join Date: Jul 2011 Location: Adelaide Posts: 4,546	--I find it hard to believe that my FA31 and FA77 are getting hammered (at the pub? ) by anything frankly. I am stunned every time I see my 31ltd shots after transferring them from the camera. It's easily the best lens I have used. Just another mediocre image with BS edge sharpness etc etc: And another one What a crap lens it is... maybe I'll just give it away. Last edited by bossa; 08-24-2012 at 09:22 PM.

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05-18-2012, 04:49 PM	#16
Rondec Loyal Site Supporter Join Date: Mar 2009 Location: Gladys, Virginia Photos: Gallery Posts: 27,653	Originally posted by VisualDarkness The (most often) higher pixel density of APS-C can lower the resolution score compared to FF and considering the pretty good border score here the 31mm could get really nice result if tested on a bigger sensor. I guess. Its just that the extreme edge on APS-C is no where near the extreme edge on full frame. So, on a D800 (same pixel density as K5), you are going to see some border weakness. On D700, probably looks pretty strong.

05-18-2012, 04:53 PM	#17
VisualDarkness Veteran Member Join Date: Nov 2011 Location: Uppsala, Sweden Photos: Gallery Posts: 4,439	Originally posted by Rondec I guess. Its just that the extreme edge on APS-C is no where near the extreme edge on full frame. So, on a D800 (same pixel density as K5), you are going to see some border weakness. On D700, probably looks pretty strong. But if the 31mm got good resolution at the extreme borders and that pixel density is less it could potentially get even greater result in the tests (vignetting will be bad though). This is of coarse nt as true for monsters like the D800.

05-18-2012, 06:33 PM	#19
Class A Pentaxian Join Date: Aug 2008 Location: Wellington, New Zealand Posts: 11,251	It all makes sense because this time it was the "31mm f/1.8 Limied", i.e., not the "Limited" lens that was tested (see the title above the MTF figures). Joking aside, I'm puzzled by the new figures. A peak at f/2.8, if true, would be extraordinary, but yet resolution figures are lower than that of the 35/2.4. This should only be possible if the 31/1.8 has relatively large aberrations that do not depend on the f-ratio. However, lateral CA seems well controlled. So what is the source (if all the figures are right)? Does anyone know of any other MTF measurements for the FA 31/1.8? Anyhow, the above is just measurebating (and of some interest to those with a curiosity for optics). I feel a 4/5 rating for the optical quality of the FA 31/1.8 is inadequate. What would a Stradivari receive at ~~photo~~audiozone.de? A 3.5 out of 5 for sound? I'm sure it has technical "flaws" and that these are part and parcel of what makes it special. Last edited by Class A; 05-18-2012 at 06:42 PM.

05-19-2012, 03:17 AM	#20
vrrattko Veteran Member Join Date: Jun 2010 Photos: Albums Posts: 753	Originally posted by Class A Does anyone know of any other MTF measurements for the FA 31/1.8? Well FA31 was also tested by Lenstip on K-5.....but they dismissed the lens as nothing special and overly expensive. That review pretty much trashed the aura of FA31.

05-19-2012, 05:16 PM	#21
Class A Pentaxian Join Date: Aug 2008 Location: Wellington, New Zealand Posts: 11,251	Originally posted by vrrattko Well FA31 was also tested by Lenstip on K-5..... Thanks for the pointer. According to their measurements the centre does definitely not peak at f/2.8, just like it did not with Photozone's earlier measurements. What is going on?

05-19-2012, 05:24 PM	#22
bossa Veteran Member Join Date: Jul 2011 Location: Adelaide Posts: 4,546	All I know is my 31 is razor sharp at all F ratios on my K-5 and that's good enough for me. I can't imagine selling that lens at all.

05-19-2012, 05:34 PM	#23
lytrytyr Pentaxian Join Date: Nov 2011 Photos: Gallery \| Albums Posts: 4,310	Originally posted by Class A I feel a 4/5 rating for the optical quality of the FA 31/1.8 is inadequate. See Photozone Rating System

05-19-2012, 05:39 PM	#24
jsherman999 Veteran Member Join Date: Dec 2007 Photos: Gallery Posts: 8,237	Originally posted by Class A Thanks for the pointer. According to their measurements the centre does definitely not peak at f/2.8, just like it did not with Photozone's earlier measurements. What is going on? Some type of sample variation? Is the newly tested sample MIJ or MIV?

05-19-2012, 11:25 PM	#25
Laurentiu Cristofor Banned Join Date: Nov 2009 Location: WA Photos: Albums Posts: 3,055	The FA 31 is one of the best lenses that Pentax produced and can stand up next to lenses produced by anyone. Lens reviews are interesting up to a point. I check them just to find out about major issues that I care about.

05-20-2012, 04:49 AM	#26
dankoBanana Inactive Account Join Date: Dec 2008 Location: Zagreb, Croatia Posts: 533	Some people seem to discover the fact that sensors do play a role in the camera output just as much as a lens. The fact is, the 31 & 43 Limiteds are designed for film and are getting hammered on a 16MP sensor by DA Limited lenses designed for digital (DA 35 & DA 40). I expect the same will go for the FA 77 on a K5. The DA 70mm will best it on edge performance.

05-20-2012, 05:08 AM	#28
zapp Pentaxian Join Date: Jul 2011 Posts: 2,385	Originally posted by vrrattko Well FA31 was also tested by Lenstip on K-5.....but they dismissed the lens as nothing special and overly expensive. That review pretty much trashed the aura of FA31. Come it, the FA31 is a nice lens ... in a full format system with AF engine from the late 80's. On an APS-C camera it is a big dinosaur. I like mine, but I also know the problems. The photozone&lenstip reviews explains all the little problems - still prainsing the lens. This thread here only shows how narrow minded the Pentax community is regarding this lens. I only keep my 31FA because I have have use for it and it would be useful on a future full frame camera as wide angle lens - it was designed as a wide angle lens not a normal equiv. lens. The 9.x rating in Pentax review does not count much in real world - almost everything is rated close to 9 or 10.

05-20-2012, 05:25 AM	#29
Class A Pentaxian Join Date: Aug 2008 Location: Wellington, New Zealand Posts: 11,251	Originally posted by jsherman999 Some type of sample variation? Even a decentred copy should have good centre performance (unless it is totally out of whack). Unless the lens is essentially damaged, the peak of sharpness should not shift (that much). Maybe Klaus changed some measurement parameters but he seems puzzled by the changed measurements for the 43/1.9 as well so I don't necessarily expect him to have an answer. Originally posted by dankoBanana The fact is, the 31 & 43 Limiteds are designed for film and are getting hammered on a 16MP sensor by DA Limited lenses designed for digital (DA 35 & DA 40). The FA Ltds and the DA Ltds have different optical designs. The FA Ltds have better peak performance but are not as consistent across the f-ratio range (A characteristic I prefer because I'm a) interested in peak sharpness and b) prefer the rendering of the FA designs. Even if it were true that the FA Ltds were outdated, it would not explain a shift of peak performance of the 31/1.9 in a retest. It would not explain a drop in border performance of the 43/1.9 either. Something is going on with the photozone retests and Klaus does not appear to have the answers himself.

05-20-2012, 05:33 AM	#30
Class A Pentaxian Join Date: Aug 2008 Location: Wellington, New Zealand Posts: 11,251	Originally posted by lytrytyr See Photozone Rating System I'm familiar with the PZ rating system and fully support avoiding inflation with ratings. However, if lenses like the FA 31/1.8 receive 4/5 then one wonders what lenses will get a rating closer to 5. Maybe a boring macro lens? Summary ratings are always problematic, but I do not think that degrading the FA 31/1.8's rating from 4.5/5 to 4/5 makes sense, if one considers the reputation of the lens with experienced photographers. Maybe other lenses I do not know of have surpassed the 31/1.8 and are more deserving of a 4.5/5 or even 5/5.