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06-07-2008, 02:30 PM   #46
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Great pics raybo. i noticed that spot, could be the lens. i've gotten the same from sensor dirt as well as lens. if its outside, easy to clean... if inside, post processing with a clone stamp gets it out in a hurry

06-07-2008, 03:53 PM   #47
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QuoteOriginally posted by ivoire Quote
Great pics raybo. i noticed that spot, could be the lens. i've gotten the same from sensor dirt as well as lens. if its outside, easy to clean... if inside, post processing with a clone stamp gets it out in a hurry
OK ivoire!

What is the proper way to check the sensor?

IIRC, f22 and a "sky shot"? I'm still pretty much a newb and would like some advice.

Thanks as always,

Ray
06-07-2008, 03:56 PM   #48
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BTW,

I have not seen the "spot" in any other images, could the magnification of the 1000mm bring out a small partical of dust on my sensor that I would not normally see?

Thanks again,

Ray
06-07-2008, 04:14 PM   #49
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Raybo, lens magnification should have no effect on the spot created by a dust particle on the sensor; that will be a fixed size regardless of which lens is mounted. Check the lens!

06-07-2008, 05:07 PM   #50
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QuoteOriginally posted by christinelandon Quote
Raybo, lens magnification should have no effect on the spot created by a dust particle on the sensor; that will be a fixed size regardless of which lens is mounted. Check the lens!
Thanks!

I will try to find a qualified person that can check the lens.

Thanks again,

Ray
06-07-2008, 07:17 PM   #51
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Raybo the lens could make the spot more noticable. Easiest way I ever found to test for dust is using a pinhole lens. Dust is etched sharp like a laser, when viewing on lcd. Mirror lens is pretty slow so you may be getting some of this effect. Also the light coming out of a long focal length lens could be more straight( telecentric) this might make dust show up sharper ( like comparing condenser enlarge head to diffusion).
thanks
barondla
06-07-2008, 07:40 PM   #52
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QuoteOriginally posted by barondla Quote
Raybo the lens could make the spot more noticable. Easiest way I ever found to test for dust is using a pinhole lens. Dust is etched sharp like a laser, when viewing on lcd. Mirror lens is pretty slow so you may be getting some of this effect. Also the light coming out of a long focal length lens could be more straight( telecentric) this might make dust show up sharper ( like comparing condenser enlarge head to diffusion).
thanks
barondla
Okee dokee like I said, I have not seen the "spot" on any other images, here is another image using my 16-45..........



Thanks again,

Ray
06-07-2008, 08:16 PM   #53
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Ray, i suspect it is the lens as i don't see the specks in this pic. to test the sensor for dust you can try the following:

"fashion a pin hole out of a piece of card stock and place it in front of the lens -- cut it to the correct size to fit in the filter threads or tape it on. Open the aperture wide open on the lens. Take a picture of a white wall with the correct exposure -- focus doesn't matter. You'll see all your dust crystal clear on the sensor.

or

"Similar to the pinhole trick, but easier to perform without makeshift materials, is to shoot a plain background at the smallest possible aperture. A shot of the brigthblue sky works well. The dust will look sharp, and really stand out...even peices of dust on the sensor that aren't visible any other way.

But if you can't see it at a more moderate aperture, it's not really a problem."

forum link with pic using#2: https://www.pentaxforums.com/forums/pentax-dslr-discussion/12921-dust-what.html

06-07-2008, 08:21 PM   #54
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QuoteOriginally posted by ivoire Quote
Ray, i suspect it is the lens as i don't see the specks in this pic. to test the sensor for dust you can try the following:

"fashion a pin hole out of a piece of card stock and place it in front of the lens -- cut it to the correct size to fit in the filter threads or tape it on. Open the aperture wide open on the lens. Take a picture of a white wall with the correct exposure -- focus doesn't matter. You'll see all your dust crystal clear on the sensor.

or

"Similar to the pinhole trick, but easier to perform without makeshift materials, is to shoot a plain background at the smallest possible aperture. A shot of the brigthblue sky works well. The dust will look sharp, and really stand out...even peices of dust on the sensor that aren't visible any other way.

But if you can't see it at a more moderate aperture, it's not really a problem."

forum link with pic using#2: https://www.pentaxforums.com/forums/pentax-dslr-discussion/12921-dust-what.html
Thanks ivoire,

I "don't" think the anomoly is on the sensor but I will give your suggestion a shot.

Thanks again,

Ray
06-08-2008, 03:52 AM   #55
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QuoteOriginally posted by Adam67 Quote
Ben,

I also have the Tamron SP 500mm. But I have just SP not the SP2; any idea what the difference is?
That is not where the difference is. I have the "BB" version. The earlier version was the "B".

Mine is an SP as well. The earlier version focus ring does not use the cross hatched rubber focus ring. It is linear.

Quote from Mirror Lens Blog:

"This is the latest of Tamrons Mirror lenses. There was an earlier model called 55B which did have some optical problems due to mirror design. All that was optimized in this 55BB model."

From Mirror Lens Source: The Mirror lens source: Tamron SP 500/8 Tele Macro model 55BB

Here is a photo of the newest version which I have. Followed by the older version which has a tripod collar.
Attached Images
   

Last edited by benjikan; 06-08-2008 at 04:12 AM.
06-08-2008, 10:12 AM   #56
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QuoteOriginally posted by benjikan Quote
That is not where the difference is. I have the "BB" version. The earlier version was the "B".

Mine is an SP as well. The earlier version focus ring does not use the cross hatched rubber focus ring. It is linear.

Quote from Mirror Lens Blog:

"This is the latest of Tamrons Mirror lenses. There was an earlier model called 55B which did have some optical problems due to mirror design. All that was optimized in this 55BB model."

Thanks.....mine looks just like yours with the checkered focus ring

edit: It does say 55BB on it
06-08-2008, 01:41 PM   #57
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QuoteOriginally posted by barondla Quote
ivorie, I had a Sigma 600 with film oly. It was a nice lens. Wasn't as sharp as the C5! The C5 really surprised me on K10D/20D. No color problems. It is a big lens. Make sure you use a lens shade (Celestron makes a flat folding one with velcro that wraps around lens). Shade is about as long as lens! Thats a lot of glass up front so the shade really is needed. Did you get the optional tube to allow a camera to be used instead of the eyepiece? It requires a T adapter. Nice system that allows you to use any slr body on same lens.
thanks
barondla

Enter POINT & SHOOT CONTEST #7 in P&S forum. Any type camera except slr. Any brand. Any subject. Ends tonight!
Is this the lens shade you mentioned?

94011 Celestron Dew Shield Foamex for 5" Schmidt Cassegrain Telescopes.

Last edited by ivoire; 04-12-2009 at 10:29 AM.
06-08-2008, 02:44 PM   #58
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Thats the one. Basically just a flat piece of plastic with velcro on the side to allow the shade to "stay together" around the tube. There is some padding at one end to help keep it in place. Is convenient to carry since its flat.
Is the Sigma lost for good? If so, thats a shame. Loved the way the filters changed in the back with pull out holders. So fast.

thanks
barondla
07-18-2008, 07:09 AM   #59
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This thread made me start looking for a mirror lens! Thanks a lot everyone, just feed that addiction with a different kind of drug

Found a Tokina 500mm on fleabay from a fairly local source who I have dealt with in the past, it arrived here yesterday. From the looks of it the thing hasn't been used in years if the amount of dust on the front of the lens is anything to go by. Everything moves smoothly and appears to be in great shape, only thing missing is a front lens cap $127 shipped isn't bad I don't think.

I am impressed by the solid construction of the lens (made in Japan makes me happy too for some reason), it reminds me a bit of the construction of the DA* 50-135 I have.

My father-in-law has a set of Pentax teleconverters sitting around his house so he is going to pass them on to me. Hopefully by the end of the weekend I'll be able to mount everything onto the tripod and take some sample pics.

Big thanks to everyone in this thread for setting me on this path, and for all the advice, especially about cleaning as I wouldn't have thought to look that up!
07-18-2008, 05:21 PM   #60
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LSR, welcome to the mirror lens world, i think you'll enjoy it. I liked the tokina so much, i sprung for a sigma 600mm. It arrived with a lens mounting flange broken off. Since i had an old 28mm lens with a lot of fungus, i removed the mount from the fungus lens, drilled a couple of holes in it, removed the sigma mount and screwed in the fungus mount (after soaking it in alcohol). worked like a charm. heres a pic from the lens:

Last edited by ivoire; 04-12-2009 at 10:29 AM.
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