Deformed Photo Subject with Sony 18-200mm

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aster
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Re: Deformed Photo Subject with Sony 18-200mm

Unread post by aster »

Hi Greg, :)

I try not to use any filters or polarizers though I have some that fit the threads of the Sony 18-200mm. I always want to see what the lens glass is capible of on its own. But I may try attaching one just to see what diffeence it can make. Still though, I don't think polarizers can fix any of the graphical distortions we see in these photos, since it's about shape-shifting and nothing that can be eliminated by specialized tools that have a mathematical constant of fixing things.

Both 18-200mm lenses I got my hands on produce the same results. I haven't seen this amount of distortion before because I never shot a white, South-facing, rectilinear facade from this distance on bright and sunny days. Usually, the over-cast, rainy, cold winter months don't produce such distorted geometry.

I actually can see the heat haze with naked eyes as it distorts the subject's shape behind it if they are 20m. or so away from me. Especially flat roofs, and metal-clad surfaces are really producing a great deal of heat and radiation visibly.

Thhe small binoculars I have around can only verify the haze effects that I already can see with naked eyes.

The conclusive result of this testing only clarifies that I probably will not want to print full-size prints of this kind of distortion at the moment....maybe later it may look interesting though. :)

Yildiz
Greg Beetham wrote:Hmm that's pretty bad alright Yildiz, all the edges look like they've been chewed by a rat, I guess the next thing too ask is, is there a filter involved? if so how is it without it? and do you have a good polarizer filter too try, just to see if that improves things, also I think you said you had two copies of the 18-250 available, do they both come up with similar results? And what about a big pair of binoculars on a tripod, or better yet a decent spotting scope on a tripod, at 20X you will definitely see mirage through the eyepiece if it's present.
Greg
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Greg Beetham
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Re: Deformed Photo Subject with Sony 18-200mm

Unread post by Greg Beetham »

Yildiz Hi, :)
here is a photo I took some time ago of the old clock tower and connecting office in town (since been demolished), the ambient was around 32-33C at the time if I remember correctly, you can use the zoom on the bottom rh corner of the browser too zoom in to 200%, and the only degredation that is readily apparent is because it's only a web jpeg at low quality and won't take much zooming, but the edges are still basically ok despite that, the thing I'm having trouble with is, why are you guys seemingly getting sooo much mirage at 20C, whilst there is hardly any here at 33C it not making a whole lot of sense to me so far. :?
Greg

ps I just read your reply before I posted the above, so then it is basically a mirage problem, and not a lens issue after all...but still, lots of mirage at such a low temp, I wouldn't have been expecting that...those roofs must be the cause, also I can't remember if high or low humidity makes it worse or not....

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David Kilpatrick
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Re: Deformed Photo Subject with Sony 18-200mm

Unread post by David Kilpatrick »

Temperature changes cause air turbulence shimmer in photos, not heat alone. A constant 30+C with very hot air can be perfectly sharp, I've shot plenty of such examples. But 20C with strong convection currents caused by hot air rising from the ground through colder air can wreck sharpness.

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Greg Beetham
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Re: Deformed Photo Subject with Sony 18-200mm

Unread post by Greg Beetham »

Oh, BTW I have a KM18-200, and I think it takes quite OK images at between 35mm and 150mm but at 200mm it's rather ordinary to say the least, still it's a useful all purpose lens just the same, provided you aren't expecting much at the wide end, or at full zoom. :mrgreen:
Greg

Ah, I just saw David's reply, you must have a mixture of hot and cold...that does make sense. :idea:
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