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10-07-2011, 10:24 AM - 1 Like   #1
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Reflections on FA31 and 18-55 kit lens

Hello everyone. Relatively new Pentaxian here who a few months ago bought a kx with the 18-55 and 55-300 kit lens. Just a short while ago, I was fortunate to acquire the vaunted FA31 f1.8 lens from our marketplace in top condition, used.

I should like to share my comments about my new prized FA31 and notes about some comparison tests that I did with it and my 18-55 kit lens at 31mm. Before I begin, I am in no way trying to imply that the kit lens is as good as the FA31. Additionally, I am strictly an amateur who has a lot to learn in the world of photography. The majority of you have forgotten more than I probably will ever know.

But, I suspect that there are some of you out there like me who are hooked on great Pentax lenses. So here goes:

1. I tested each of the two lenses with two Imatest charts printed on 8 1/2x11 paper that I downloaded and taped to a box. The tests were indoors with natural lighting and two overhead ceiling fan lights turned on. Manual focus using Liveview, ISO 400, aperture priority. At f1.8, 2.8 4.0, 5.6, 8.0, 11.0 for the FA31 and 4.0, 5.6, 8.0, and 11.0 for the 18-55 at 31mm. (Hereinafter, I will refer to the 18-55 at 31mm as "55S." To attain 31mm, I guestimated the zoom ring to what I thought would be as near 31mm as I could --- about halfway between 24mm and 35mm.)

Bottom line: At f4.0 and up, the FA31 had better sharpness and less fringing than the 55S. Verdict: Definitely FA31.

2. I next tested the two lenses with pics of a pot and vase sitting on the edge of our fireplace, with a french door facing north behind the fireplace. That gave me an opporunity to judge pic IQ and purple fringing through the door frame. Same parameters as for the above: ISO 400, manual focus, aperture priority, f4.0, f5.6, f8.0, f11.0.

Bottom line: slight edge to the FA31. What really got me here was just how the 55S hung in there in a real world picture setting. FA31 better at the edges; 55S either equal to or slightly not as good as the FA31 in the center. Since the 55S at 31mm fastest setting is f4.0, it came as no surprise that the edge sharpness was not as good as the FA31 at f4.0. (I have read the Photozone reviews of the FA31 probably two dozen times, fyi.)

3. This morning I took some pics facing north from our upper deck here in south central New Mexico. ISO 200 with Auto Focus, aperture priority. Apertures compared: f4.0, f5.6, f8.0, f11.0, f16.0.

Bottom line: At all apertures, the FA31 appeared better in terms of overall IQ, in my opinion. For several pics, the results were somewhat close though. Again, I note just how decently the 55S hung in there.

4. As a means to amplify my notes about how the 55S competes fairly well, I should like to share 6 pics from test 3. above, at f4.0. The first two are the pics right out of the camera. In my eyes, the FA31 is better. But, again, the 55S hangs in there pretty good for this scene. The other four pics are crops, two of which are some houses near the center and the last two are at the right hand edge of the scene. I was surprised at just how decent (and even a bit better) the 55S crop looks for the two houses near the middle. Of course, no surprise that the FA31 is sharper at the edges.

Summary conclusions and comments. I very much like my FA31. It will stay on my camera most of the time. But, the 18-55 kit lens is not chopped liver. I am amazed at just how good the over 600 pics are that I have taken. I will keep it for sure. Interesting at how a $50 lens hangs in pretty good for decent lighting pics compared to a hall of fame $1000 lens. No bokeh comparisons, but just a small sampling of ordinary real-world pics with good lighting conditions.

I suppose some of what I am saying parallels Ken Rockwell's essay: Your Camera Doesn't Matter.

.....................................

Here are the uploaded pics. FYI, the FA31 pics resulted in a shutter speed of 1/2000 and -1 exposure bias. For the 55S --- 1/1250 and 0 exposure bias. As you can see, the FA31 pics were exposed a bit less. Not exactly sure why they are different in the same light, but it is what it is.

1. FA31:





2. 55S:



3. FA31 scene crop 1:



4. 55S scene crop 1:



5. FA31 scene crop 2:



6. 55S scene crop 2:




Last edited by altovintner; 10-07-2011 at 02:04 PM.
10-07-2011, 10:41 AM   #2
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I realise that too, the 18-55 is not bad at all for a 50$ lense

the FA is always used with 1/2000 shutter speed, the 18-55 is at 1/1250.

i can't do any conclusion with this observation, but i find it funny.
10-07-2011, 10:49 AM   #3
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QuoteOriginally posted by aurele Quote
I realise that too, the 18-55 is not bad at all for a 50$ lense

the FA is always used with 1/2000 shutter speed, the 18-55 is at 1/1250.

i can't do any conclusion with this observation, but i find it funny.
I always thought the kit kens is good but not that good. I think I will keep it instead of selling it for $30.
10-07-2011, 11:27 AM   #4
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QuoteOriginally posted by altovintner Quote
Relatively new Pentaxian here who a few months ago bought a kx with the 18-55 and 55-300 kit lens. Just a short while ago, I was fortunate to acquire the vaunted FA31 f1.8 lens from our marketplace in top condition, used.
QuoteOriginally posted by altovintner Quote
who has a lot to learn in the world of photography
May I suggest that you stop pixel peeping and take pictures instead of charts before you start to be more interested in gear rather than photography?

10-07-2011, 11:32 AM   #5
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QuoteOriginally posted by Zav Quote
May I suggest that you stop pixel peeping and take pictures instead of charts before you start to be more interested in gear rather than photography?
I think you probably are right.
10-07-2011, 11:48 AM   #6
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+1

Pixel peeping can easily lead to LBA which can get very expensive, very quickly.
10-07-2011, 12:16 PM   #7
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QuoteOriginally posted by jatrax Quote
Pixel peeping can easily lead to LBA which can get very expensive, very quickly.
And?

Is this a problem?

I manage to keep my LBA contained. Before I can buy something, I must sell something else. As long as the money just goes into and out of my PayPal account instead of a house charge account, I can do whatever I like. Like, buy a few more lenses...

@altovintner,
+1: nice comparison. Now you need some 24-28-35-40-45-55mm glass for further cross-checks. Gee, I'll be listing a 24, some 28's and 50's, and a 55 real soon now. What a coincidence.
10-07-2011, 12:17 PM   #8
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Thanks for sharing!

I'm curious whether or not using a tripod (assuming one was not used) would reveal more difference in sharpness?

10-07-2011, 12:41 PM   #9
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The kit lens is capable of making good images, especilly stopped down a bit. This was handheld at 33mm and f5.6
10-07-2011, 12:42 PM - 1 Like   #10
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I should include the image, eh?

10-07-2011, 12:54 PM   #11
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QuoteOriginally posted by civiletti Quote
The kit lens is capable of making good images, especilly stopped down a bit. This was handheld at 33mm and f5.6
Wow. Great pic!

...................

Stills999: I did use a tripod on all of my pic tests.
10-07-2011, 01:02 PM   #12
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The kit lens club is full of excellent examples of what the kit lens can do. It is a decently sharp lens when shot at f/8-11. f/5.6 is also quite good if at the wide end, but then again there is a lot of barrel distortion at the wide end. But clearly what it can't do is remain sharp at f/5.6 or larger apertures at 31mm or greater. This can get limiting quite quickly in a number of settings. The 31 ltd is in a class of its own in this regard. Nevertheless, there's no discounting the little kit lens - no wonder it is considered the best kit lens amongst all other kit lenses around. Great little travel lens.
10-07-2011, 01:58 PM   #13
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QuoteOriginally posted by Ash Quote
The kit lens club is full of excellent examples of what the kit lens can do. It is a decently sharp lens when shot at f/8-11. f/5.6 is also quite good if at the wide end, but then again there is a lot of barrel distortion at the wide end. But clearly what it can't do is remain sharp at f/5.6 or larger apertures at 31mm or greater. This can get limiting quite quickly in a number of settings. The 31 ltd is in a class of its own in this regard. Nevertheless, there's no discounting the little kit lens - no wonder it is considered the best kit lens amongst all other kit lenses around. Great little travel lens.

Hello Ash. Well said!

FYI, about a month ago I went to a friend's 60th birthday party with my 18-55+kx and took pics as my gift to him. Well, he was pretty happy with what I gave him. Moreover, there was a lady there who had been a professional wedding photographer for over 10 years. She asked if I would take some pics of her and her husband, which I did. As luck would have it, two pics that I gave her pleased her very much. She was stunned at the quality attained with what I was using, in that she was used to toting around thousands of dollars of Canikon camera gear.
10-07-2011, 02:30 PM   #14
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I use my kit lens with DxO, and frankly I think pics look as sharp, if not even a bit sharper, than my DA 40 pics (including the corners). The good thing is DxO is going to support the DA 40 and the DA 70 soon. If only it supported the Sigma 10-20...
10-07-2011, 02:49 PM   #15
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QuoteOriginally posted by stills999 Quote
Thanks for sharing!

I'm curious whether or not using a tripod (assuming one was not used) would reveal more difference in sharpness?
At that shutter speed (1/1250 sec.) probably not. It gives you consistent framing which is handy. The framing is more important if you use AF for focusing. If the camera is seeing the same scene, AF should be similar, but AF can be way off if the scene is framed differently and the point falls on something else to focus on. AF can introduce too many possible variables for a test like this.
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