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I own a Tamron 18-270mm F/3,5-6,3 Di II VC PZD lens - a fabulous lens, but since I got it (around Christmas time), the autofocus has been playing up; see below image.

noticetheblur.jpg

EXIF is as follows:

270mm, 1/100 sec, f/6.3, ISO 100, no flash.

notice the terrible focusing; it's been doing this whenever the sun isn't super-duper bright (it's fine then). Is there anything wrong with my lens? The blur (or non-focusing, rather) in this image was not caused by camera shake.

Interestingly enough, when I try to manual focus, the result isn't much better. Maybe I'm just blind?

EDIT:

below is an image I took this morning of the same place; there was more light, which is nice, but the blur still remains. I cleaned out every inch of my lens and camera, so a dirty lens is not the culprit.

blurrypic2

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    I had this lens(came with my 500D purchased in used condition), and here's my 2 bits of advice. It has fundamental focusing inconsistencies at the longer end. Also, longer end focusing is also a bit soft. Stopping down does not do much good. I purchased a camera brand kit zoom lens, and donated this lens to a photography student because of this very reason. Macro and closeups are where it shines. Zoom to fit the subject into your frame and fire away, it will not disappoint you. Try getting the AF Calibration done by a proper camera service center. – ATG Apr 5 '18 at 7:34
  • @ATG thanks a lot, mate! So, you think I should send it in to TAMRON? – bearmohawk Apr 5 '18 at 8:28
  • Yes, if focus misses all across the zoom range, ask them to fine tune AF or calibrate VC. Check close up shots first, if they are fine, then its not an AF / VC issue, but an inconsistency, which they cannot fix. If so then use this lens for macro only, and don't hold high hopes for zoom performance from this. In my opinion, a lens which has such a zoom range, offering versatility, will be a bit weaker in other areas such as the said lens. Case in point is that, most camera kits have an 18-55 and a 55-200/250 or a 70-300. They do not include a lens which goes from 18 all the way to 200+. – ATG Apr 5 '18 at 8:39
  • @ATG yup, makes sense. If you look here: 500px.com/photo/244284143/stream-in-the-forest-by-ondrej-gomola you see that it's relatively ok at 18mm, and if you poke about my other pictures, you see that when there's lots of light, it works great, even at 270mm. – bearmohawk Apr 5 '18 at 8:43
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    Its a great lens, and even if my comment made it seem so, you can live with it. Your pics are great as well. I donated mine, only because it didn't suit my purposes (bird and wildlife photography), and the pics are mostly captured at full zoom. – ATG Apr 5 '18 at 9:07
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You've got at least two things working against you in lower light.

  • Less contrast for your camera to use to focus
  • Less usable signal (light) with which to make a picture

Since both phase detection autofocus (SLR using the viewfinder) and contrast detection autofocus (Live view or mirrorless) uses contrast to determine what is in focus, less contrast in the scene gives the camera's AF system less to work with. Most cameras are programmed to focus as accurately as possible without taking too long to do it. As a result, in low light such cameras will be less accurate with regard to AF.

A lower signal to noise ratio usually means the camera will apply more noise reduction in dim light, even at ISO 100, than it will in brighter light. Noise reduction tends to reduce image detail along with the noise.

Focusing, both auto and manual, are usually done when the aperture is wide open. The camera will only stop down to the selected aperture value the instant before the image is captured. The wider the aperture of the lens, the better the camera's autofocus can perform. Your 18-270mm f/3.5-6.3 lens is relatively slow, especially on the telephoto end where wide open the aperture is only f/6.3. That's right on the fringe of what most cameras' PDAF systems are capable of using to AF at all. Even when shooting at narrower apertures, a wide aperture lens gives an advantage to AF systems over a narrower aperture one. You might try using Live View based contrast detection AF instead. It will probably be much slower in low light, but should be more accurate if you've managed to properly tell the camera where it is you wish it to focus. Your sample image, for example, is very well focused on the area with the highest amount of contrast in the scene at the extreme lower right.

  • thanks! If you look at the picture, it's very hazy (almost cloudy). If you look at my now edited question, I added some pictures. What do you think is causing this? – bearmohawk Apr 4 '18 at 8:06
  • It still appears to be slightly focused in front of what you were presumably aiming at. The overall performance is in line with what I would expect from that lens. – Michael C Apr 4 '18 at 17:10

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