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09-12-2007, 10:49 PM   #1
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Lemon or over-expecting? FA 20-35

So after reading several reviews about how people have used the FA 20-35 f/4 lens as a normal lens for their K10's, I went out and shot a day with mine on instead of the 18-55 kit lens. I'm a little confused with the result, and I wish I had similar images from the 18-55 to compare these with, but I didn't get it out of my bag. I seem to be getting a lot of Chromatic aberration. Do I have a lemon 20-35 or am I just expecting too much from a tough situation?

Both pictures taken around 6:00 PM.
First picture:
K10D, 20mm, 1/320 and f/8, ISO 400, no crop.


Second:
K10D, 20mm, 1/800 and f/5.6, ISO 400, roughly 100% crop from middle of far right side


These have been down-sized for the web, the originals look a tad bit worse in regards to CA.
Thanks for your help!

09-13-2007, 12:24 AM   #2
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Better take a same shot with your kit lens and see if there is any difference. The FA20-35 is a very good lens, especially on film. But on digital SLR, I think it's over rated by some owners. I had the same lens three times, but prefer the DA16-45/4 (and now the Sigma 1770) better ...
09-13-2007, 02:46 AM   #3
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I had one (had to sell it to pay bills). I loved the size and the image quality (sharp and plain nice rendering) and so really liked the lens but yes the CA was pretty shocking. photozone shows up to 2.4 pixels at its worst. i also found it comes in blue, green, red, yellow as well as purple fringing.
09-13-2007, 06:00 AM   #4
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I have an FA-J 18-35 which came as the kit lens with the *istD. Normally I don't take kit lenses, but the FA-J18-36 was a full frame lens, and could be used on my PZ-1 as well, as an ultra wide.

I have been very pleased with it, and not noticed any serious issues with CA on shots taken with it either on film or digital.

Now that I have gone fully digital, and have a Sigma 10-20, the 18-35 (and PZ-1 for that matter) get no use.

Note however, I am not normally a pixle peeper, and generally look at images based upon the size I want to view/ print them at, not pixel by pixel.

09-16-2007, 06:59 AM   #5
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Do a more objective comparison.............

I just received a used FA 20-35mm f/4 AL which I purchased from another member of this forum. Well, from the short time I have been testing it, I can say that I am very happy with its IQ. If you do some exhaustive research in the net and read as many reviews and opinions as you can on Pentax wide angle zooms, you will realize that CA seems to be a common problem with most Pentax wide angle zooms at the wide end. Even the vaunted FA 50 f/1.4 prime suffers from CA at f/1.4!

One thing I can say about the FA 20-35mm, and I have a used lens originally purchased by the seller in 2004 (3 year old lens!), it is very sharp wide open, it has beautiful color rendition (very close to the FA 50 f/1.4) and bokeh, it's CA is more controlled than other Pentax wide angle zooms, and it is 2/3rds the size of the DA 16-45 f/4 compacted, and 1/2 the size of DA lens extended!! In other words, the FA 20-35mm gives you a much more compact lens with equal IQ and better CA control than the DA 16-45mm.

I suggest you give yourself and your lens more time to get acquainted with each other and learn its idiosyncracies. Only after that will you really get to appreciate its strengths.
09-16-2007, 07:28 AM   #6
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sampe shots with Fa 20-35mm

As an addendum, here are some sample shots I made today. All at 20mm, f/8, RAW then PP'd using my standard workflow adjustments through RawShooter and CS2....











While these shots have been sharpened and resized for posting in this Forum, I can safely say that a 100% crop of the original photo showed no significant signs of CA, considering that there are strong highlights since some shots are facing the light.
09-16-2007, 08:41 PM   #7
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QuoteOriginally posted by clawhamemr Quote
I seem to be getting a lot of Chromatic aberration. Do I have a lemon 20-35 or am I just expecting too much from a tough situation?
That is normal. CA could be a problem with both FA20-35 and DA16-45 at the wide end, and these two are comparable in terms of CA.

However, resolution and rendering qualities are excellent. Mechanical construction is very good as well. Surprisingly, according to Photozone tests in terms of resolution FA20-35 at 20mm appears to be slightly better than FA20 (prime!!!) and just slightly worse than DA21mm Limited (again prime, this time limited!!!). Very good for a wide-angle zoom!

Other three major characteristics of any lens are not of primary concern these days anyway: vignetting, distortions and CA can be easily and efficiently fixed in any common post-processing and image editing tool.

My opinion: I owned both DA16-45 and FA20-35 and I sold DA16-45. My AF lens kit consists now of FA20-35, FA28-70 and FA35/2AL. No DAs. (Once available, DA17-70 may replace my two FA zooms, but only if better than Sigma 17-70 and comparable to Nikkor 18-70mm.)
09-16-2007, 09:19 PM   #8
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So yeah, after doing more tests comparing the two I have determined that I just jumped the gun and am a little too paranoid. the 20-35 has replaced the 18-55 as my 'normal' lens, and now that I've got a 50-200 I don't miss the 55mm setting anymore. It seems sharper and doesn't seems to be actually better at control chromatic aberrations. Thanks for all your input!

09-18-2007, 04:33 AM   #9
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I don't know why anyone would recommend such a limited focal range for a DIGITAL SLR. It becomes a 30-52.5mm lens. Very restricted for a zoom, not particularly wide, not particularly fast. Should be great to use on your ZX-L though!
09-18-2007, 06:04 AM   #10
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Oh yeah, it's excellent on my ZX-L, I love it. Sure it doesn't go quite as wide as the 18-55, but I quote a member from the dpreview pentax forum: 'Go with what makes you happy. Anything less makes you less happy.' And personally, the 20-35 works for me.
09-18-2007, 06:12 AM   #11
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I dig that.
09-18-2007, 06:18 AM   #12
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but on another subject, how's the 16-45? I've thought about getting that, but the only advantage over the 20-35 seems to be the wider/longer range.
09-18-2007, 06:25 AM   #13
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The FA 20-35mm is, in my case, a great street zoom for a DSLR. It goes from medium wide (30mm in FF) to the optimum FOV which is between 45-55mm in FF. For portraiture and close ups of plants and flowers, I have an FA 50 f/1.4. The 20-35 is compact and covers the range that I mostly shoot in. A super wide angle (12-24) may be nice to have, but I doubt if you will use it as often as the range of the 20-35.
09-18-2007, 06:45 PM   #14
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QuoteOriginally posted by clawhamemr Quote
but on another subject, how's the 16-45? I've thought about getting that, but the only advantage over the 20-35 seems to be the wider/longer range.
That's pretty much it. However, there is one disadvantage of DA16-45: size and weight. FA20-35 is about the size of DA18-55 (as a reference) and does not extend too much at 20mm. DS+FA20-35 makes very nice small and light portable kit. (Once I noticed that DA16-45 usually stays at home while FA20-35 always goes with me, I sold DA16-45.)
09-18-2007, 07:33 PM   #15
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QuoteOriginally posted by SupremeMoFo Quote
I don't know why anyone would recommend such a limited focal range for a DIGITAL SLR. It becomes a 30-52.5mm lens. Very restricted for a zoom, not particularly wide, not particularly fast. Should be great to use on your ZX-L though!
It depends on your style and preferences. I personally like small and light lenses and FA20-35 is small and light enough. I don't like super zooms. Also, I prefer using primes and I often carry my DS with FA35/2AL only. But when I am expecting tighter spaces instead of carrying several primes FA20-35 serves me well as a lens I can use as a normal lens with an option to go wider if I am forced to. And I seldom have to go wider than 24mm.

One interesting note on focal lengths: Apparently there is an agreement among some (if not most) photographers that the most pleasing perspective can be achieved with focal length that matches the diagonal of a film/sensor. For 35mm film it is ~43.3mm. I believe it is no coincidence that Pentax decided to go with 43mm for their first Limited film lens (FA43/1.9). I also find M40/2.8 very useful on my MX and I use it more often than 50mm, 35mm or 28mm.

Since APS-C sensor diagonal is ~28.3mm the perfect "normal" lens for APS-C would be 28mm. FA20-35 fits that bill perfectly: 28mm is right in the middle of the range covered! So FA20-35 is to me something like an "adjustable" perfect prime for the APS-C format DSLR.

(Considering all this I am surprised that there is nothing like DA28/2 Limited on the DA lens road map.)
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