lescrane said:
someone in this threat complained that the lens is a dust sucker. I was shooting at beaches and wetlands for two weeks. Lot's of sand hit the camera/lens. Back from the trip and cleaned the exterior thoroughly. Nothing got inside that I can see. I did keep a 95mm B&W MRC filter the lens to protect front from sand and spray. I note that the tamron has a rubber gasket at the base of the mount.
As mentioned before, no problems at all. except maybe a few missed BIFs as per usual poor user technique.
Great! I'm glad that sand doesn't enter into the barrel, otherwise Tamron would have to make a serious recall. However, dust is naturally much smaller and flatter than sand granules, and regardless of having the same 95mm protective filter on the lens, extending the barrel to 600mm allows for water droplets and dust particles to attach to the exposed barrel section of the lens. So when taking a fast action handheld photo of an Osprey, soaring 90 degrees from the horizontal, and zooming quickly in and out to make sure the bird is mapped onto the full frame sensor, those little particulates bypass this lens’s gasket placed between the top section and the cork-screw internal receiving mechanism. Everyone's lens will display different build characteristics to a very controlled degree, but continual inconsistencies are a sign of poor engineering. For a few extra hundred dollars to the consumer, Tamron could have made the extra effort in ensuring better design for longer use life. As a direct comparative example, my prime series Tamron f/2.8 24-70mm (stronger and thicker seal in the barrel) and 70-200mm (internal focus) lenses have the gold ring marking with excellent sealing and solid build design that feel like professional lenses and were designed to compete directly with the Canon 24-70 / 70-200 lenses. For its well-designed optics, Tamron should have not compromised the 150-600mm. A colleague of mine also purchased the Tamron 150-600mm, and after a few weeks of use, he also acquired a very similar count of internal dust. Deciding to service it himself and remove the front element and apparent dust on the first internal element down the barrel, he removed the 4 screws of the outer plastic mount and an additional 4 lower mount screws holding the front glass element to the housing. (NOTE: Many photographers know how to perform standard surgery on their lenses, given their limited time, budgets, and demanding schedules.) Naturally, Tamron has been very worried about material weight to improve lens portability, so the parts had a light but flimsy feel to them (a little pressure holding the ring in your hands, and the plastic can crack). However, what's worse is that when he showed me the removal of the front glass element, pieces of metal spacer filings started falling out from the sides with an uneven count. The actual glass sits on top of 4 separate sets of layered metal spacers that are physically hand placed in their grooves (not well-defined and move around easily) so that the glass can be suspended (minimizes vibration shock). Nevertheless, the tolerances of the metal spacers are not consistent, and even from the factory, an uneven number of spacers are placed underneath the lens, altering alignment by 1mm, even when placed in their appropriate groove (design and quality control issue). Furthermore, the top glass sits in its housing without any sealing, and so it was easy to see how dust particles could now enter from the top and the barrel chamber wall. Using masks to avoid any spitum, gloves for optic handling and to prevent oil smudging, in addition to a controlled system vacuum and hand held blower, the majority of dust was immediately removed. However, we noticed that two of the "dust" specs that initially caused the need to open the lens, were actually moisture spots that had dried on the underside of the front element and the surface of the first inner element. Again, knowing how they got in was very surprising and discomforting. Using lab grade micro-fiber lens paper, sterile throat swabs w/out glue, and high grade methanol, the spots were carefully and successfully removed without producing any scratches. Blowing out the chamber one last time, it turned out that reassembly became a struggle, given that the layers of spacers kept falling out whenever remounting the front glass element. This is a bad design issue that you don’t have with prime Canon lenses and some entry level Canon lens bodies (i.e. EF-S 55-250)! I have had my Canon 100-400mm f/4-5.6L for 3 years in very demanding environments, and the number of internal dust specs is less than or equal to 3 on the frontal element while remaining clear on the internal elements. Additionally, the build design doesn’t have loose parts and the cleaning process is a breeze given the solid metal components and well-designed tolerances in the machining! For many people, the Tamron 150-600mm will be “good enough” to compete with the market and create a ding in the oligopoly (traditionally Canon and Sigma for long range telephotos on EF DSLR mounts) of lens pricing, while obtaining comparable results to the big white whale brother lenses. However, for many professionals, the compromise of build quality is not acceptable and having to open your lens very early on and void the warranty is not a sign of a healthy relationship with your lens!
