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01-11-2013, 10:44 PM   #1
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Round aperture

Hey guys, I was just wondering which pentax or non-oem lenses has round aperture blades. I do know that the 40xs and the 55 1.4 has em, are there anymore "New/digital" lenses for pentax that has round aperture blades?

01-11-2013, 11:03 PM   #2
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D FA 100mm WR does I think
01-11-2013, 11:17 PM   #3
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There's nothing in the wider end I guess?
01-11-2013, 11:21 PM   #4
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QuoteOriginally posted by kaiserz Quote
There's nothing in the wider end I guess?
There's also the 40mm XS and the DA 50mm. Here's a complete list:
rounded Lenses - Pentax Lens Reviews & Lens Database


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01-12-2013, 05:07 AM   #5
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Just btw, I suggest you buy lenses based on other criteria, because the shape of the blades isn't really that important. If you compare the 40mm ltd and the 40mm XS, I doubt you could notice a difference in most situations. Or the old and new 100mm macro.
01-12-2013, 05:17 AM   #6
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The DA 18-135 has rounded aperture blades.
01-12-2013, 07:51 AM   #7
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Thanks guys (: I was kinda looking at a wider angle lens something like a 28, 30, 35. I do know that the 40xs is a wonderful lil lens (I have it) and that the 55 1.4 is an awesome lens (Next on my list to purchase.) but then wondered if there's a wider prime lens in there with the same characteristics as those two that I mentioned. But I'm guessing that there won't be an OEM cause apparently it's a "pentax thing" RiceHigh's Pentax Blog: New Pentax Circular Lens Aperture Patent
01-12-2013, 07:58 AM   #8
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Round blades the most hyped thing at the moment for lenses...

01-12-2013, 08:00 AM   #9
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QuoteOriginally posted by Na Horuk Quote
If you compare the 40mm ltd and the 40mm XS, I doubt you could notice a difference in most situations. O
I even believe the shape of the aperture is the same...

The only thing that you will notice are the highlights in the background, those will appear rounder but that does not make a brake an image at all...
01-12-2013, 08:45 AM   #10
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QuoteOriginally posted by Anvh Quote
Round blades the most hyped thing at the moment for lenses...
Yeah, it's like sliced bread!
01-12-2013, 09:25 AM   #11
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Not sure what you intend with that statement.
01-12-2013, 09:44 AM   #12
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That's a reference to an idiomatic expression in English. The latest, greatest fad is often referred to as "the greatest thing since sliced bread."
01-12-2013, 10:10 AM   #13
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I know but did he intent it as a pun or like something serious?

He's afteral seriously looking for one...
01-12-2013, 11:04 AM   #14
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It all depends on whether you like sliced bread

As for the "round" aperture opening. Here is a general breakdown:
  • The greater the number of blades, the rounder the opening
  • Large number of blades are sort of incompatible with auto-aperture (lens stops down automatically at exposure time), particularly if high exposure rates are part of the design objective
  • Many preset and fully manual aperture lenses have high blade counts and essentially round aperture
  • Curved blades help when the blade count is low
  • Shorter focal length lenses, especially vintage primes, tend to have lower blade counts. For example, my S-M-C Takumar 28/3.5 and Tamron 28/2.5 both have only 5 straight blades.

Now, to put things in perspective...
  • The professional quality lenses for my view camera only have five straight aperture blades
  • Even high acclaimed optics may have low blade counts. For example, the 35/2.8 Zuiko on my Olympus XA only has two! (Yes, the aperture is square.)
  • Round or regular plane figures are not the only options. Some of my FSU rangefinder lenses have a fun-looking curved pincushion look to them.
Finally...

If you truly want round, SHOOT WIDE OPEN!


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01-12-2013, 11:19 AM   #15
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Ha ha! I remember some of the 120 film Point and Shoot cameras I used as a kid had a rotating metal disk with round holes of various diameters as the aperture. Indeed I think the same system was used on some Instamatic and later disposable 35mm cameras. The joys of fixed shutter speed cameras.
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