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NX5U - 6 blade iris diaphragm

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Gene Kois
NX5U - 6 blade iris diaphragm
on Dec 18, 2011 at 10:10:07 pm

I've had my NX5U for 22 months and I absolutely love it. I've shot in a wide range of run & gun and studio situations. Hope I don't jinx it, but I've never had any problems other than the early no TimeCode and long upload times for LPCM audio. But FCP 7.0.3 fixed all that up. About 7 months ago, I got the Hood Loupe from Westside AV, and that really made it a great handheld camera. Having said all this, there is one thing about the camera I can't figure out.

Quoting from the Official Sony Brochure for the NX5U: Six-blade Iris
 The six-blade iris diaphragm is nearly circular, enabling the creation of an extremely beautiful background blur.

This background blur... I think it's been called bokeh... is like the Holy Grail with so many producers I work with, and it seems to be most evident with cameras using the very large chips. But in all the vastly different shooting situations I've been in over the last 22 months, I have never really seen this "extremely beautiful background blur" with the NX5U. Wait... I take that back. Once I shot an interview at night on a ridge top with the city lights in the background literally miles away. It looked really cool. And if I go full wide on the zoom and just get very close to the subject, I can soften the background by slipping into macro focus. But I don't think either of these situations has anything to do with the 6 blade iris diaphragm.

Does anyone have any experience or insights with this on the NX5U? Is there something I'm just not doing or quite understand? The only mention of "blur" in the manual is on page 30, and it's just a very simplified explanation of Depth of Field.

I certainly didn't buy the camera based on that one paragraph description of this effect, but it would be nice to see it.

Thanks.

Gene Kois • Specific Video
Kailua, Hawaii


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Michael Johnston
Re: NX5U - 6 blade iris diaphragm
on Dec 18, 2011 at 11:12:42 pm

With all cameras, if you shoot zoomed in halfway on a subject, you'll get a blurred background as ling as the subject has some distance from the background. With the NX5's six blade, you simply get more blur than other similar cameras. Zoomed all the way out, you really won't notice. It's when you start zooming tight that you notice the difference.


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Gene Kois
Re: NX5U - 6 blade iris diaphragm
on Dec 19, 2011 at 1:04:29 am

You're definitely right. I didn't mean to imply my "full wide zoom/macro" trick is the way I normally shoot. Especially on interviews, I'm always looking for that focal length/f stop combo that gives me the most control over the background sharpness. It's just that nothing I've seen out of the NX5U is any more dramatic than my old PD-150 or PD-170. Did they have a 6 blade iris? I don't know.

I just don't see the 6 blade iris that Sony specifically refers to in its marketing doing anything different than other 1/3" chip cameras. It's interesting to me that Sony would highlite it like it is something unique to the NX5U.

For example, the marketing hype for the Canon XA10 (and a number of its other camcorders) says: "In contrast to a typical 6-blade iris, the XA10’s 8-blade iris captures extraordinarily smooth out-of-focus ‘bokeh' for a more attractive image effect. The additional blades also reduce diffraction of light passing through the iris, allowing for the use of smaller apertures while maintaining image quality."


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Michael Johnston
Re: NX5U - 6 blade iris diaphragm
on Dec 19, 2011 at 4:05:49 am

I can definitely show you screen grabs of interviews I've done that show the NX5 is definitely better than other 3 1/3"chip cameras. You have to be careful not to buy into the marketing hype too much. Yes, the XA10 has 8 blades but it also only has a single 1/3" chip. You really have to look at the specs to understand a camera. Notice how Canon does not specify a minimun illumination for this camera. BIG RED FLAG. As for focal length/f stop, on 2/3" cameras the ideal f stop is 5.6. However, with 1/3" chip cameras, it's more like 1.6 to 2.4 because you need as much light as possible getting to those smaller chips.


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Stephen Crye
Re: NX5U - 6 blade iris diaphragm
on Dec 19, 2011 at 5:27:42 pm

Gene, 6-blade iris is nothing special. Here is the way to test. Point at something that has bright glints - water, a back-lit leaf, etc. Go to full zoom. Then de-focus. All the glints will turn into little hexagons. With an 8-blade iris, they will be little octagons. the more blades, the better the "bokeh"

You can also use this method to see lens imperfections (an old trick that amateur astronomers use)

The NX70s I've been testing have 6-blade, and I'm not thrilled with it.

Big, expensive pro cams have 12-blade or higher. You will see this on TV or movies.

Here's some sample frame-grabs from the NX70:

http://www.huecotanks.com/temp1

Steve

Win7 Pro X64 on Dell T3400, MultiTB SATA, 8GB RAM Vegas 10e x64 DVDA 5.2(build 133) Sony HDR-CX550V


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