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Archive 2012 · Pentax 20 mm. f/4 vs. Zeiss 21 mm. Distagon
  
 
igmolinav
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p.1 #1 · Pentax 20 mm. f/4 vs. Zeiss 21 mm. Distagon


Hi,

I saw at a shop a 20 mm. f/4 from Pentax. Has anyone tried it?

In the following review they say the following:

Addendum July 2011.
I have now been able to compare K20/4.0 to the Zeiss Distagon 21/2.8 - a lens with well known cult status and reference point value. The trivial part of the conclusion is that K20/4.0 no longer feels heavy More importantly, as far as image quality is concerned, K20/4.0 performs on the same level as the Distagon as far as center resolution is concerned; in the corners, the Distagon wins. Also, there is more purple fringing and somewhat more distortion in the K20/4.0. Overall, my appreciation for K20/4.0 has risen in the comparison: the Distagon is the better lens, but the Pentax lens is definitely a very good one.

From PentaxForums.com: http://www.pentaxforums.com/lensreviews/SMC-Pentax-K-20mm-F4-Lens.html#ixzz2GLTOrpzW

If it is good in the center, perhaps one could use it with a camera with an APS sensor as a 30 mm. lens(?)

I found another review, but it may not be for the same lens:
http://www.pentaxforums.com/lensreviews/SMC-Pentax-K-20mm-F4-Lens.html

There is a Nikon adapter sold on E-bay to be used with it.

Thank you, kind regards,

igmolinav : ) !!!





Dec 28, 2012 at 11:43 AM
wiseguy010
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p.1 #2 · Pentax 20 mm. f/4 vs. Zeiss 21 mm. Distagon


Strange conclusion of the review in your post. First they conclude the Pentax is just as good as the Zeiss. That statement is followed by some (major) points where the Zeiss is better.


Dec 28, 2012 at 12:12 PM
jcolwell
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p.1 #3 · Pentax 20 mm. f/4 vs. Zeiss 21 mm. Distagon


I owned the SMC Pentax 18/3.5, and it wasn't as good as the Tamron SP 17/3.5 [151B], Tokina AT-X 17/3.5, and Voigtlander Color Skopar 20/3.5 Asp SL II. Now, I own the Zeiss 18mm f/3.5 ZE, and it blows them all completely away. The 21 ZE is slightly better than the 18 ZE, but since getting the TS-E 24/3.5L II, I never used the 21 ZE, and so I sold it, to help pay for a TS-E 17/4L. I picked up the 18ZE for the frequent occassions when the TS-E 17 & 24 are just too big and heavy to bring with me.

Here's some old reviews of the 18mm and 20mm Pentax lenses. The first one (BOA) hasn't been available online for many years. The second one (Stan Halpin) is still available online.

http://home.att.net/~alnem/html/equipment_review.html
Last Updated on Monday, November 08, 1999 BOA's Gallery: Pentax Lenses Review

18mm

K18/3.5 is an excellent rectilinear lens; it is quite large and bulky though. It's correction of spherical and coma aberrations seems far better than that of A20/2.8, and it is surprisingly sharp edge to edge. Its coma wings are also smaller than those of K24/2.8, K28/2, or K30/2.8.

Yoshihiko Takinami also notes that the corner resolution of K18/3.5 is higher than that of A20/2.8, and the only defect of K18/3.5 seems to be the lack of normal or UV filter though it has four filters built-in.

BTW, there's no A18/3.5.

20mm

Among f2.8 versions of K, M, A, F, and FA lens, A seems to be the best with excellent contrast, color rendition, barrel distortion. OTOH, it's not as good in resolution, coma aberration and contrast in the corners as K15/3.5 or K18/3.5, even closed down.
FA version is said to have the same optical formula as the A version, and to be very sharp in the center when stopped down. Not much vignetting , but slight "droplet" distortion was mentioned once. All 20mm lenses are said to have great build and prices to match.

K20/4 and the M20/4 produce very slight distortion. K20/4 is also known to flare. However, when comparing K20/4 to K18/3.5, Nikkor 20/2.8 AIS (current model) and Tokina 17/3.5 (current model.), the K20/4 still beats them in every aspect, especially flare control.

http://stans-photography.info/
• 18 mm f/3.5
Yoshihiko Takinami - an excellent lens, IMHO. It's spherical and coma aberrations seem far better than those of an A20/2.8. Its coma wings are also smaller than those of K24/2.8, K28/2, or K30/2.8.
Yoshihiko Takinami (again) - very sharp, good color saturation, well flare controlled, few light-fall-off even at wide open
- - - - - -
Pål - . . . I love the 18/3.5 lens. I bought mine new in 1978 and I'll guess I will keep it forever. . . Its a lens thats capable of sharp images. Avoid wide apertures and F:22, where corner sharpness really suffers. It also a bit warm in color; it has skylight, cloudy, red and orange filters built in and you have to use one of them.
Pål - [Again] . . . This is a lens with "faults". It isn't really sharp until F: 5.6 and it has very soft corners at F:22. Its also very warm and when I have shots one the same roll with this lens and my other lenses I can easily pick out the ones shot with the 18mm due to its color cast. These factors may be serious for some. For me it doesn't matter; I usually use a wide angle like this at F: 5.6 and smaller apertures and the color cast doesn't usually bother me much.
- - - - - -
Barry Brevik (From the Web) - Excellent lens, one of my favorites. I have been using the 18mm f3.5 for about 15 years. This is a superb ultra-wide. Flare is extremely low and the lens is very sharp. It is physically similar to the 20mm f4 (which I also use) except for a rear mount gelatin filter clip and a built in filter wheel. You are forced to use one of the four filters on the wheel, one of which is a skylight. The skylight does not seem to influence the color rendition in any way when compared to the 20mm f4 (with no filter) on the same role of film. Hands down, one of my favorite Pentax lenses, and one of my favorite lenses regardless of maker. Filter size is 58mm, but in practice most filters vignette.
- - - - - -
Joe Cali (From the Web) - The 18mmf3.5 is a very sharp contrasty lens even at fairly wide apertures. I occasionally use it at f3.5. The image quality suffers a little at the edges. Stop it down to f5.6 and wow, the images really pop out at you. The colour saturation is fantastic. I sometimes joke that it must have a built in polarizer. It has built in skylight, yellow and orange filters. The filter thread is 58mm. You can hold a bare cokin type filter in front of the lens but screwing anything in the filter thread results in vignetted corners. With the built in filters and the high contrast of the lens, I've never found this to be a problem. In Australia, I've only ever seen one of these lenses for sale second hand. I bought it and didn't regret it. It really is a superb lens.
- - - - - -
Yoshihiko Takinami - An excellnet performer !! Few distortion, great flare control for an 18mm lens. It also has remarkable uniformity in image quality from center to corners. I really love this lens. :^)
- - - - - -
Pål - Hmmm. Mine is certainly soft in the corners wide open and at F:22. Otherwise I agree that its a great performer.
[and in another comment . . . ] Avoid wide open and F:22. Excellent quality at mid aperture. Very warm color rendition. Flare control good for an 18mm lens.
- - - - - -
Daphne - . . .this is a fan-tastic lens!!! resolution is great, light loss at the corners is minimal, it is sharp... and i just love the field of view.
Oh Cheng Yu [from the web-response form] - no noticeable light fall-off at full aperture, but softness at edges. Very sharp slides when stopped down to f/8
________________________________________
• 20 mm f/2.8 A
Ken Kuo - The SMC-A 24mm/2.8 is a gem . . . . . . it's my standard lens. Razor sharpness, no noticeable distortions, excellent contrast, compact, and has no "polycarbonate" parts.
- - - - - -
Douglas J Stemke - . . . I love this lens; I've only had it for a short time but really enjoy it. Very sharp. The biggest problem is the hood; Pentax sells it for $80 which seems way too high to me for something that is really that simple. . . Although I haven't used it a great deal, I can't yet claim to see any significant distortion on it, but will look more critically on some of my shots tonight and give you a better idea.
- - - - - -
> For mostly deliberate landscape shot, which do you recommend, FA or A, and why?
Yoshihiko Takinami - I prefer A20/2.8 to FA20/2.8, and actually own a A20/2.8. They are optically identical except the number of aperture blades. . . I recommand MF for this range of focal length because you would not tend to focus on the subject but on the hyper-focal distance. As for the number of aperture blades, you won't be able to distinguish between the two, five or six. The only one exception would be bright spotlights in background, six lusters by six blades, and ten lusters by five blades.
> A version is considerably more expensive than FA version, why?
I suppose the helicoid mechanism of MF lens is more expensive to produce than gears of AF lens.
- - - - - -
Rob Studdert - I also own the Pentax A20/2.8 and would like to add that it is of exceptional build quality and as a consequence is a joy to use.
[and in an added later comment from Rob] . . . It is a great lens (great contrast, high resolution and good flare resistance) but it is expensive (even used).
- - - - - -
Yoshihiko Takinami - . . . I own A20/2.8, which is optically identical to FA20/2.8 except the number of aperture blades; FA has 6 blades and A has 5 blades. This optic is the best one among the Pentax 20mm lenses, IMHO, with great contrast and excellent color rendition.
It's a pity but its not so good in resolution, coma aberration and contrast in corners as K15/3.5 or K18/3.5, even closed down. To confess the truth, I prefer K18/3.5 or K15/3.5 to A(FA)20/2.8 in terms of optical quality. Unfortunately K18/3.5 seems very rare and K15/3.5 is expensive.
- - - - - -
Patrick Rendulic - I did some tests with this lens and must say that its performance is quite amazing. I am also very happy that there is no visible vignetting when using a Pentax SMC UV filter (67mm thread) or my Contax linear polarizer. So tomorrow I will go and order some Pentax SMC 67mm filters for B&W photography. Just wished they were not so expensive (the UV cost $US65).
- - - - - -
Fred - At the 20mm focal length, I am familiar only with the A 20/2.8, but I can recommend it without reservation . . . It has become my most used wide-angle below 28mm. (In fact, I recently sold my A 24/2.8, not because I didn't like it, but I found that I just didn't use it as much anymore, after getting the 20/2.8.) While I am unlikely to dig out and lug around the A 15/3.5, unless I know I have a need for it, the A 20/2.8 goes with me everywhere whenever I'm "photo-equipped".
Except for the wide (67mm thread) filter mounting flange in the front of the lens (which nicely helps avoid vignetting when using filters, and I frequently do use a polarizer on it), the lens is actually quite compact. It is fast, . . . and that is useful, but it is also both sharp and quite low in distortion. Its flare performance is good and its contrast is quite high. On the other hand, its "official" "dedicated" hood is sort of a screw-in "big round pie plate with a hole in the middle", and I do wish that Pentax had come out with a rectangular hood for this lens instead. (I don't use the hood too often on the lens, but I am able to get 75 satellite channels on it when hooked up to the TV.) Oh, I almost forgot to mention, . . . the A 20/2.8's build quality is very high. . .
________________________________________
• 20 mm f/2.8 FA
jostein.oksne Sep 1997. . . I've had the lens for one and a half years. It is rectilinear and pretty much so too. Hard to see any bending lines at all. It suffers from a weakness common to almost all super-wideangles, though. A kind of distortion that works like this: if you focus on a circular dot in the center of view, and move your camera so that the dot goes towards a corner, it will gradually change shape to a droplet. And I don't think it comes out excellent in MTF-tests either.
Nevertheless, I use mine often, and think of it as a very convenient lens. Manual focussing is ok (I've got an MX), and it can take Cokin filters without vignetting. . . The horizontal view is 118°.
- [additional, more recent, comment from Jostein] - I've had the lens for 3-4 years. I used it a lot the first six months, but less with time. These are my experiences:
Sharp, also in the corners. probably less than half a stop vignetting in the corners. Takes a Cokin P-series polarizing filter (4mm thick plus ring) without vignetting (tested this in a situation where I was sure there would not be any light falloff from the polarising).
Very low barrel distortion.
One problem, though: there is what I call "droplet distortion" towards the corners. It works this way: A circular spot will be circular at the center of the frame, but if you move the camera so that the spot approach a corner, the spot will take on the shape of a droplet with the pointy end towards the frame center. To me this is quite annoying sometimes, especially if there are highlights in the corners.
Rob Studdert explains . . . I think that you will find this "droplet distortion" apparent in any photographs captured with lenses with a wider than normal field of view. The design of a rectilinear wide-angle lens causes elongation of objects radially from the centre of the frame, the wider the angle of view (lower the lens focal length) and the further from the centre of the lens the distortion becomes more apparent.
This distortion can be minimised by re-mapping the rectilinear image to a cylindrical view (panoramic) using Panorama Tools from Helmut Dersch http://www.fh-furtwangen.de/~dersch however new (but possibly less distracting) distortion is introduced (vertical linearity is preserved but horizontal lines become distorted).
[Editors note: Imagine a cone of light . . . smh]
[Editor's second note: A polar bear is a rectangular bear after the appropriate transformation . . . smh]
- - - - - -
Daphne - . . . [this] was my favorite lens [since sold] - razor sharp excellent contrast no distortion..came in useful for both indoor shots and background foregrounds effects. Actually i liked it so much that i bought its A equivalent. . .
- - - - - -
Roberto Burgos S. - I do own this lens and find it superb. I recently shot some landscapes for a cliente, and while making a couple of 8 x 12 enlargementes (Kodak royal 25 film), ther was one white spec on the negative that seemed like dust. After close inspection and cleaning of the negative, it happened to be a house! about 3 miles away. We made an enlargement of the section (equivalente to a 40 x 60 inch inlargement) and surprisingly, found that not only the Kodak Royal 25 film is great (grain similar to a 400 ISO FILM on a 12 x 18 inch enlargment), but the little spec on the negative, had the house and we could count the windows!
Beware only of thick ring filters, even regular polarizers because they will vignette (67 mm filter size). I found that Cokin Optilight filters which have a thin ring do not vignette.
Yes the FA20/2.8 is a great lens, but its also very pricey (about $550 mail order) and more expensive than the FA24/2* (which I also have but I like the 20 better). I do not have the FA28/2.8 but I've heard its one of the best damm 28's ever built by any manufacturer. If you can go for the 20/2.8 (F, FA or A, they are all the same optically) you will never regret it. Its a superb lens.
- - - - - -
Yoshihiko Takinami - . . . I confirmed that A20/2.8 and FA20/2.8 are optically identical except the number of aperture blades. . .
________________________________________
• 20 mm f/4.0
Gerjan - please avoid this lens unless you want it as a fine 'collectible'. Also avoid the SMC Pentax-M 1:4 20mm. Both lenses have a double form of distorsion (barrel and pincushion). The edges of the image are unsharp unless you stop down to f/11 or higher. Edge contrast is quite fine though. If you want a good 20 mm you should buy the 1:2.8/20 A or the new 1:4/20-35 mm AF zoom.
Gerjan - [again] Although some mebers of this group tend to disagree on this 20 mm topic, I still think that the 2.8/20 or the new 4/20-35 are the only viable alternatives. I don't like the 4/20 K nor the 4/20 M for their distortion. The 2.8/20 and the 20-35 zoom are not 100% distortion-free either, but if you do not take pictures of walls directly from upfront you will not see any distortion. The 2.8/28 M/A is not one of Pentax' best products (except for weight and dimensions), the FA 2.8/28 is far better, but not 100% distortion-free either. If you really need an almost distortion-free wide angle lens, go for the 3.5/28 K or M. Distortion is under 0.5% for both.
- - - - - -
Barry Brevik - . . . for me this is a great lens. It is, in fact, one of my all time favorites in terms of image quality, and the coatings are superb. If the front element is clean enough, I can take pictures that contain the Sun without getting any lens flare. . . . As for polarizers, I have not yet found one thin enough to not vignette. My only problem with the 20mm is that the f4 max aperture coupled with the dim viewfinder of the MX is a drag, so you might want to look for the more modern 20mm f2.8 M series lens, depending on which body you are using.
- - - - - -
Gianfranco Irlanda - I do not use it very often due to its aperture (I tend to prefer something faster) but I think it is a good lens. The sharpness is great in the center, but it tends to be rather soft towards the corners when wide open (the corners do not satisfy me much but I haven't done any serious test). It has a noticeable light fall-off @ f/4 that disappears when closed around f/8. It is a nice lens for its weight and size. I payed something like . . . quite expensive for a very used one but it was the only 20mm Pentax I'd ever put the hands on...
________________________________________
• 20 mm f/4.0 M
[see Gerjan's comment on 20 mm f/4.0 above.]
- - - - - -
Texdance - I have the SMC-M 20/f4. I carry it everywhere. It is extremely small, and certainly fast and sharp enough for my purposes. My 20mm gets used less than my 24mm and more than my zoom that goes to 18mm.
- - - - - -
Michael Sharkey - . . . At f/4 the corners are rather on the soft side. The corners are quite sharp at f/8 and then the overall sharpness seems to drop off a bit as you get to f/16 and beyond.
On the same roll of film, I shot the same wall area with my KA 28 f/2.8 just for comparison and got much more pleasing results toward wide open end. Anyway, I think the 20/4 will likely prove to be a nice lens for shooting outdoor 'scapes.



Dec 28, 2012 at 01:41 PM
igmolinav
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p.1 #4 · Pentax 20 mm. f/4 vs. Zeiss 21 mm. Distagon


Hi,

Thank you for your posts and the links : ) !!!

I'll read them and then get back to you !!!

Kind regards,

igmolinav : ) !!!



Dec 28, 2012 at 03:24 PM
 

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Cadaver
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p.1 #5 · Pentax 20 mm. f/4 vs. Zeiss 21 mm. Distagon


A question for jcolwell. Which did you prefer, the Tamron SP 17/3.5 [151B], Tokina AT-X 17/3.5? thanks.


Dec 29, 2012 at 01:13 PM
jcolwell
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p.1 #6 · Pentax 20 mm. f/4 vs. Zeiss 21 mm. Distagon


Cadaver wrote:
A question for jcolwell. Which did you prefer, the Tamron SP 17/3.5 [151B], Tokina AT-X 17/3.5? thanks.


I preferred the Tokina. I posted some comparison images in these threads.

tokina 17mm 3.5 http://www.fredmiranda.com/forum/topic/1124317/0#10736542
17mm tests 17-40L vs AT-X http://www.fredmiranda.com/forum/topic/957560
Canon 17-40 vs Oly 21mm f/3.5? http://www.fredmiranda.com/forum/topic/986355
17mm f/3.5 Primes: Are they all the same? http://www.fredmiranda.com/forum/topic/953918/
Tamron vs. Tokina 17/3.5 UWA testing http://www.fredmiranda.com/forum/topic/932789/0

By conicidence, I'm just about to go out to take some comparison images with my new Zeiss 18/3.5 ZE, TS-E 17/4L, and EF 16-35/2.8L. I'll post the results on the Canon forum...



Dec 29, 2012 at 01:23 PM
igmolinav
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p.1 #7 · Pentax 20 mm. f/4 vs. Zeiss 21 mm. Distagon


Hi,

Thank you again : ) !!!

Kind regards,

igmolinav : ) !!!



Jan 07, 2013 at 02:00 PM





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