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I just bought a secondhand 18-200 tamron lens but I can't seem to get a fully sharp picture. I know my settings and the picture is "smudged" blurry and seems to have some color artifacts on one side and on the other side on a similar focal length it is sharp. It seems like there Is an uneven Oily on the second glass if I keep it on an angle I tried to clean it but it won't go off.

Could this be a damaged coating? Is this problem fixable or did I simply waste my money on this?

The image is made on F8 1/200 200iso

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    Can you take a photo of the lens itself and of what you see which makes you think the issue might be a damaged coating? – mattdm Feb 24 at 16:13
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    What do you mean by "the second glass"? – mattdm Feb 24 at 16:28
  • What is the first picture supposed to show? It seems to have been over post-processed... – xenoid Feb 24 at 16:31
  • @mattdm - Maybe "second glass" is a focal-length converter? – xiota Feb 24 at 22:05
  • @xenoid - Looks like low JPEG quality settings to me. – xiota Feb 24 at 22:06
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[Not enough for a full answer, too much for a comment.]

I don't know whether that's a lot worse than expected, but it is expected on that type of superzoom; green-red chromatic aberration to the outside of the frame.
It would probably help a bit if you could tell us what focal length you shot this at - the effect increases at longer lengths.

I found a review of it at Amateur Photographer - Tamron 18-200mm f/3.5-6.3 Di II VC review in which they show examples with very similar, if slightly less exaggerated chromatic aberration.

It's the type of distortion that can be compensated for reasonably well in Photoshop/Camera RAW etc if you shoot in RAW rather than JPG.

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It's a little hard to tell from your examples, but I think you are saying that there's a consistent difference in sharpness (and possibly chromatic aberration) on one side of the frame compared to the other.

If that's the case, this is unlikely to be a damaged coating. This is usually a de-centered or slightly tilted lens element.

Nothing is perfect, and all photographic lenses have compromises in order to reach their design goals. This particular lens has sixteen glass elements in fourteen groups. These elements enable the huge zoom range and other features like internal focus, image stabilization, and reasonably close (although not macro) focus. All of that in a package that sells for $200 retail brand new.

Even the most expensive lenses aren't absolutely perfect. (See this Lens Rentals blog post on copy-to-copy variation in geeky detail.) They're made to be as close as possible to perfect within quality control tolerances. More expensive lenses can have more fine tolerances (and often are built with more ability for technicians to adjust). Lower cost lenses — and especially complicated lower-cost lenses like your super-zoom — by economic necessity have wider tolerances for acceptable flaws.

So, it's not terribly surprising to see something misaligned. It's really hard to tell how bad this is from your samples, but you shouldn't expect miracles from this lens. It's possible that had you bought this new, you could send it in for adjustment under warranty, but very likely that they'd send it right back with a note that says "tested: within tolerances". This is camera-warranty speak for: Dude, it's a $200 lens. Our profit margin on this was already, like, two dollars. Please don't waste our time.

More on tilted and decentered lens elements at: Left part of image is much softer than the right part: decentered lens or bad M42-EOS adaptation?

Some people deal with this by buying dozens of copies of cheap lenses and returning them until they get one they feel meets their personal standards. This is not very fair to your camera store, however — the economic bargain the vendor is making with you (high-featured super-zoom for peanuts) has the camera store stuck in the middle.

My main advice is to not pixel-peep. This lens isn't meant to create wall-sized gallery prints. It's meant for taking pictures for Facebook and Instagram, for family vacation postcards and maybe some 8×10" prints. And, I think even with flaws (remember, everything in this world is flawed!) you can use it to take perfectly lovely photographs.

If, on the other hand, that's not what you want, I suggest instead spending about 10-20× as much as you did on this lens on two or three nice prime lenses — this is the most economical way to get high quality lenses which require less design compromise and can be closer to the optical ideal.

Or, if you don't have 10-20× the cash just burning a whole in your pocket, you can, like me looking at the Leica S system, think "well, that'd be lovely, but I have to work with what I have, and I'm not perfect at that, so I'll figure out how to make do". Oh, and also: you mention "second glass", which makes me think maybe you have a filter over the front element. This very well may be part of the problem — see Is a UV Filter required/recommended for lens protection? on that.

Also, What image-quality characteristics make a lens good or bad? may be helpful in thinking about all of this.

  • I suspect the lens, with respect to sharpness and aberrations, is normal because OP appears to be comparing edge performance with center performance. – xiota Feb 24 at 20:54
  • I'm really unclear on that, but, yes, possibly. In that case, a decentered element can in fact be responsible for worse than expected edge performance, but everything I said about tolerances and super-cheap super-zooms is still in play. – mattdm Feb 24 at 21:37
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Based on the images you've shown, it looks like you are comparing edge performance with center performance. It's expected that the edge and corners won't be as sharp as the center. The trees and ground on the far left and right of the frame appear about equal, as far as I can tell (there are significant JPEG artifacts, which is clearly seen as banding in the sky). So in this respect, your lens appears about normal.

  • Superzooms, in particular, are renown for their poor image quality.

The washed out appearance of the crown of a tree next to the building looks like glare. Since the sun appears to be on that side of the image, it could be normal behavior for that lens. If you have a lens hood, consider using it. If you have a filter on your lens (as mattdm suspects), consider removing it.

A picture of the "second glass" would be helpful to clarify what you are describing.

  • If it is a a focal-length converter that screws on to the filter threads, it is likely a source of many of your problems. Consider removing and disassembling it to use the macro portion as a magnifying glass (away from any camera). That is about all that such lenses are good for.

  • Teleconverters, focal reducers, and adapters with optical elements can cause hot spots in images.

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