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K-7 with 500mm F6.3 Rokinon mirror lens
Posted By: jogiba, 08-18-2009, 10:41 AM

I just received my 500mm F6.3 Rokinon mirror lens today and tested it with my K-7 in HD video mode handheld with SR on at close range of 6 ft and about 300 ft.

YouTube - First test of Pentax K-7 with 500mm F6.3 Rokinon mirror lens handheld at 6 ft close focus and SR on
YouTube - Pentax K-7 test with 500mm F6.3 Rokinon mirror lens handheld with SR on a hazy ,hot and humid day


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08-18-2009, 10:52 AM   #2
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Contrast is surprizingly good. Few 100% crops could be also useful.
Next time use good tripod, please.
08-18-2009, 11:11 AM   #3
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QuoteOriginally posted by tr13 Quote
Contrast is surprizingly good. Few 100% crops could be also useful.
Next time use good tripod, please.
I wanted to see how it would be handheld, I have much better long lenses for tripod use.
YouTube - Pentax K-7 test with Orion Apex 127 and F6.3 focal reducer (970mm F7.6) in 1536x1024 *** mode


YouTube - Pentax K-7 with Celestron 9.25 and F6.3 focal reducer (1480mm F6.3) in 1536x1024 *** HD video mode



Last edited by jogiba; 08-18-2009 at 11:17 AM.
08-18-2009, 11:17 AM   #4
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I agree - while a tripod would help overall, contrast is really surprisingly good for a mirror lens. I suppose the larger-than-usual aperture really helps there. And it seems sharper at close focus than either of the mirror lenses I've used. I had a hard time deciding between that one the even cheaper Samyang-made 500/8, or finding an old Tamron adaptall (considered one of the best mirror lenses). I like, but don't love, the Samyang-made Vivitar I ended up - it's main advantage is being half the weight. I had been thinking of someday getting myself a Tamron too, but who knows.

08-19-2009, 11:05 AM   #5
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BTW I just shot the same videos on a tripod and it's much better.
YouTube - First test of the Pentax K-7 with 500mm F6.3 Rokinon mirror lens at 7 ft close focus on a tripod

YouTube - Pentax K-7 test with 500mm F6.3 Rokinon mirror lens mounted on a tripod
08-19-2009, 11:09 AM   #6
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First still test shots with K-7 & 500mm F6.3

Click link to view full 4672x3104 jpegs taken in automatic Green button mode.
Pentax K-7 - a set on Flickr



08-19-2009, 08:34 PM   #7
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Wow, this is exactly the kind of thing I want to see! Fantastic report on the Rokinon, and on all the lenses you've uploaded videos of. I love seeing things done hand-held as well, since that's usually how I'm using my camera.

Thanks!

08-19-2009, 08:51 PM   #8
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I hate to say this, but is that the dreaded vertical green line on the third photo (front of the Chevy) running above and below the "8" on the licnese plate on the "original sized" photo on Flickr?
08-19-2009, 10:38 PM   #9
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From Pentax Germany:
Question:

After a longer video recording or longer use of Live View, there is a thin bright line in the middle of the photos taken right after that.

Answer:

This problem is known. The reason is in the heating of the sensor. During Live View and Video, the sensor is constantly supplied with current, heat is developing. In additions to these, external conditions such as summer sun and ambient temperatures are also playing their part in regards of sensor heat. When after a longer use with the relevant external conditions a photo is taken, excessive thermal noise across the middle of the sensor can occur. The next step the camera takes is to switch off automatically. Once the sensor cooled down, the thermal noise disappears again.

Handle the camera and the sensor like you would handle films "cool and dry".


It was hot out and I did have LV on for a long time when I took that shot.
08-20-2009, 04:34 AM   #10
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QuoteOriginally posted by jogiba Quote
From Pentax Germany:
Question:

After a longer video recording or longer use of Live View, there is a thin bright line in the middle of the photos taken right after that.

Answer:

This problem is known. The reason is in the heating of the sensor. During Live View and Video, the sensor is constantly supplied with current, heat is developing. In additions to these, external conditions such as summer sun and ambient temperatures are also playing their part in regards of sensor heat. When after a longer use with the relevant external conditions a photo is taken, excessive thermal noise across the middle of the sensor can occur. The next step the camera takes is to switch off automatically. Once the sensor cooled down, the thermal noise disappears again.

Handle the camera and the sensor like you would handle films "cool and dry".


It was hot out and I did have LV on for a long time when I took that shot.
Makes me question ownership of the camera in central Florida, where it is neither cool nor dry. Why all the extra effort and hype about "weather sealing?"

What is odd about this is the most recent ad on the back cover of this month's Popular Photography highlights those very two features: "Movie Capture" and "industry-leading weather resistance." "Heat" is definitely a major component of "weather."

Last edited by gfmucci; 08-20-2009 at 04:48 PM.
08-20-2009, 06:54 AM   #11
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Someone from the UK posted this on DPreview Pentax SLR forum:
QuoteQuote:
I received my replacement K-7 today (#3384xxx c/w #3377xxx) and the problem is not apparent. I did an extended test on it and the dreaded green line didn't show. I'm cautiously optimistic emoticon - smile
Re: Patheitic?: Pentax SLR Talk Forum: Digital Photography Review

BTW it's impossible to see in anything other than full 100% 4672 x 3104 .
1600px 1063px JPEG

Last edited by jogiba; 08-20-2009 at 07:08 AM.
08-20-2009, 08:39 AM   #12
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QuoteOriginally posted by gfmucci Quote
Makes me question ownership of the camera in central Florida, where it is neither cool nor dry. Why all the extra effort and hype about "weather sealing?"
Well, you don't want to store anything in a *lame and wet* place, do you?

It's weathersealed, not necessarily *airtight.* I have no idea why they suggested dry-ness, though.

Am I right in thinking, by the way, that my K20d's flash housing would interfere with one of those Rokinons?
08-20-2009, 08:44 AM   #13
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I have about 1/2" clearance between the lens and K-7 housing.
08-20-2009, 08:53 AM   #14
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QuoteOriginally posted by jogiba Quote
I have about 1/2" clearance between the lens and K-7 housing.
Hrm, assuming you're measuring from the K-7's tightest spot, however much that sticks out, one of those might just squeak by on a K20d. I've been wondering.

Anyway, as far as being in a hot place, well, that's just an exacerbating factor: keeping any sensor running is going to make heat, and it's got to go somewhere: the hotter the ambient air, and possibly the more humid, it's just that much harder to dissipate it.

It's one of the reasons, actually, I was in the 'Who cares about video' camp: I wouldn't be willing to put too much of that kind of wear and tear on the machine, considering how long it might have to last me.
08-21-2009, 08:16 PM   #15
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Put a 500 6.3 Phoenix mirror on the K20D with no problem. It cleared the flash over hang (glad thats gone on K-7).

All else being equal making a mirror lens faster decreases contrast because the central obstruction has to be bigger to handle the bigger beam of light. The Phoenix did have quite good contrast for a mirror.

thanks
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