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Old Jul 25, 2008, 2:33 AM   #1
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I have my own 'photo sniper' I made myself with a rescued Sigma 400mm 5.6, gray coloured, rescued from a junk shop with broken auto focus and a mount I did not recognise. It has been fun for a few years though with the broken iris I could only use it fully open.

Today the postman bought me a 'beige' version of the same lens but this one is manual focus and proudly proclaims itself 'APO'. But what is really good is that this one is in sparkling condition externally (though it has a patch of fungus :roll and a full 'A' type Pentax mount!


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Old Jul 25, 2008, 6:30 AM   #2
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for those that don't know..........
stay away from the non-APO, non-AF, non-macro version of this lens.. it's a lens you do not want.
john, the APO version is a lens i,ve seen great images from.

Roy
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Old Jul 25, 2008, 6:34 AM   #3
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john,
how about a shot of your sniper???
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Old Jul 26, 2008, 12:59 AM   #4
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Picture NOT taken with a Pentax! :-) I have shown this 'sniper' before with the previous lens.

The pistol grip is fitted with a two stage switch and a cable for the Pentax *ist. The handle at the front twists and turns the lens focus via a cable connection made from fishing trace and curtain wire.



The weather is terrible today, Saturday, so not chance to try out the lens yet!
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Old Jul 26, 2008, 3:34 PM   #5
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Looking forward to some photos from it John!

Dawg
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Old Jul 28, 2008, 6:52 PM   #6
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Hmmm... I took it to "the man" today to have the fungus cleared and he showed me a most horrific infestation when he shone the right sort of light into it with one lens being almost totally fogged!:roll: He does not think there is actual damage though being an internal focussing lens it will cost a pretty penny to be scrubbed out.

Oh well! :sad: I tell myself it is good to take something that is in poor condition and put it rights and even be able to use it.:G

It does raise question in my mind though, is the APO achieved throughclever coatings or by glass densities?I am thinking if a clean will bring it back to new or will some of the better characteristics be lost?:O



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Old Jul 28, 2008, 7:28 PM   #7
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John Hill wrote:
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It does raise question in my mind though,¬* is the APO achieved through¬*clever coatings or by glass densities?¬*I am thinking if a clean will bring it back to new or will some of the better characteristics be lost?:O
Hi John,

Congrats on the lens! -- and though that looks like a neat setup, using one around the Chicago Metro area, I'd probably end up with a lengthy vacation in Cook Cty Jail while they try to figure out how I hid a weapon in what kinda looks like a camera. . .:-) The focus by cable is a nice touch!

AFAIK, the fungus attacks the coatings, but APO (apochromatic) refers to the glass used in some of the elements. The index of refraction (amount it bends light) is much closer for the spread in wavelengths that make up visible light, so there's less of a tendency to create CAs (chromatic aberrations) and PF (purple fringing) which are caused by the different wavelengths (which determine color) being refracted either more or less according to the color).

APO (also called LD (Low Dispersion) by Tamron, ED (Extra low Dispersion) by Pentax, or SD (Super low Dispersion) by Tokina) glass is considerably more expensive than regular optical glass, so it's a marketing point, a desireable feature for the user, and makes the lens more expensive. Although these designations don't guarantee that a lens is good optically, for the most part, mfgs don't usually waste APO glass on mediocre lens designs.

One more thing, if you do get the lens cleared of the fungus, there will probably me more of a tendency to flare because the coatings will probably be compromised, so I'd always use a hood, and do some experiments shooting in the general direction of the sun to see just where you might expect this flare to make a difference in the shot.

Your lens tech could probably answer the question of effect on IQ better than I, but if it was that hard to see, my guess would be that except for the added potential to flare, IQ shouldn't be compromised significantly.

Scott
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Old Jul 28, 2008, 9:44 PM   #8
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Deleted by me, double post!




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Old Jul 28, 2008, 9:49 PM   #9
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Thanks Scott, yes I am rather proud of my focus mechanism!:-) I am thinking of developing my design somewhat and maybe making another 'sniper' or two to offer for sale as I have a small number of lenses in the 400mm range though this one is my 'best' the others being older and mostly M42 (i.e. screw) mount. Of coursemy design would not have the 'factory' pistol grip but I do have some reasonable tools to make something appropriate.

The Russian 'Foto Snaiper' had a curious mechanism where the first trigger pressure released a sping loaded gizmo to stop the lens down and I have thought of doing something similar with the old preset lenses. Not necessary of course with this Sigma lens.



The Foto Snaiper also had a 300mm lens which I assume someone thought was the practical limit for what is a hand held camera but I find the 400mm is perfectly practical providing I use fast shutter speed and lean against, or on,something.

Your comments regarding the lens and coatings are very reassuring. I usually would use a hood and one is incorporated in the lens.

People do tend to look twice when I carry my rig down the street but it is more curiousity than any inclination that I have a sinister device slung from my shoulder. Of course it sometimes draws the wrong type of attention and I have to do a show and tell for some stranger!:-)




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Old Jul 31, 2008, 1:51 PM   #10
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Hey John!

This is the same exact lens that I posted about a few months back! I've had great success with mine.......

http://forums.steves-digicams.com/fo...mp;forum_id=94
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