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12-27-2013, 09:13 AM - 1 Like   #16
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Thanks a million to all of you helping me understand how the "prime lens works" after going through responses I got, I decided to keep the DA 50mm f 1.8 and use the extra $$$ I was going to spend on FA50mm 1.4 toward the DA35mm f2.4. I'm very happy with these 2 primes and newly purchased Metz 52 AF-1 flash gun.
I actually did get my K-5 II with 18-135mm however I sold the "kit" zoom as it wasn't too practical for my needs now, bringing price of the body to $500 ( I have 4 months old daughter) hoping by the time she will get older I will be able to afford 50-135mm f2.8 and with 2 primes I already have I should be set for a long time. Love Pentax.
I have used Nikon D7000, canon 40D, 60D with 24-105mm L f4 and few mega zooms, Sony alpha a77 with f2.8 kit lens and 70-210mm f4 Minolta lens, but this puppy simply shines as being very user friendly and high ISO is phenomenal for being aps-c sensored camera.
Thanks once again

12-30-2013, 06:44 PM   #17
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Generally, lenses are not at their sharpest wide open. I think that the general rule (I could be wrong) is that lenses are typically at their sharpest when they are stopped down two or three stops down from the maximum aperture. Of course, this also depends on the quality of the lens. Like I said, I could be wrong. After all, I was married once.
12-30-2013, 07:27 PM - 1 Like   #18
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As noted, you will not be able to use the viewfinder to focus manually with any degree of certainty below f/2 (or is it 2.8?) without changing focusing screens. Autofocus on fast lenses sometimes needs some manual tweaking to be perfect. Using live view zoomed in 4-8x helps immensely, but it's best on a tripod so you don't inadvertently move that fraction of an inch to lose the thin slice of in-focus area.

You might want to check out a Depth of Field calculator: Online Depth of Field Calculator

At 1.8, on a 1.5x crop factor camera, a 50mm lens focused on something 5 feet away has a slice only 2.52 inches thick in focus. The 1.4 would have a slice only 2 inches. (A 1.2 lens would bring that down to 1.68 inches if you want to go really crazy).

BTW, that 50-135 may leave you wishing you had more width available if you're going to be photographing a kid indoors. Might want to look at one of the 20-something to 70something lenses. Maybe by then Pentax will have a da* version of one. But you can get an FA 28-70 f/4 for $50-100 (not the 28-80, it's apparently a terrible lens?), and it has pretty good reviews. I use Tamron 28-75 f/2.8 and it seems to be a good range for my 1 year old niece.
02-28-2014, 04:47 AM   #19
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Oh just one more thing. Those awesome "wide open aperture" photos you see online are usually heavily processed. You can add sharpness and contrast in post. Unless you are buying the Zeiss Otus, you won't get tack sharp photos wide open straight out of the camera. But most of the time you will be taking photos around f5.6 anyway (in sunlight or with flash), and the DA 50mm f1.8 should perform very well around there

And buying the DA 35mm instead of the FA 50mm f1.4 is a good idea, I think. Check out the DA 35mm plastic fantastic club on this forum, lots of great photos. Its pretty sharp wide open, too, but it also improves significantly when you stop down one or two stops.

02-28-2014, 05:12 AM   #20
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Prime Time?

Hello droneek75, Welcome to the Forum!
Those two DA primes will be useful for years, I've been impressed with mine. The fifty is hard to nail exact focus wide open because of the shallow DOF and A/F limitations, but around f/2.8-4.0 provides great isolation, contrast and bokeh. 50mm on APS-C is a great short tele effect, candid and portrait length.
The 35mm has fast focusing, sharp even wide-open and is a fine all-around prime.
In the meantime, you might keep an eye out for couple of Legacy primes, A/F or M/F, to fill in gaps. For example, a 100mm-135mm prime and 24mm prime would fit in pretty well, providing some options in different photo situations.
Just an idea for you, good luck!

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