I recently bought a Sigma 18-250mm F3.5-6.3 DC HSM Optical Stabilised Lens for my Canon 600D Digital SLR Camera. Some of the reviews on Amazon made it clear that, with such a long zoom range, there would be some compromise on image quality; but overall the lens got a good rating.
I’ve had the lens for a few months now. While I like the flexibility of the zoom range (I’m not serious enough to want to carry around additional lenses), I’m not so happy with the image quality. But I can’t tell if this is due to the fact that the lens is a compromise or that I’ve been been sent a faulty model.
Below are three photos that show the nature of the problem — generally a halo or soft-focus effect around sharp edges. Admittedly it’s mostly apparent when displaying the images at their maximum size in flickr, but I’d like to know if this is typical. If you have any idea, I’d appreciate a comment.
London Eye – vislible ‘glow’ around the struts.(Large size)
Seagull – chromatic aberration around the top of the bird’s head? (Large size)
Roof repairs – again, an unintended soft-focus effect? (Large size)
Zizzi’s Pizzeria in Bromley has gone for the science geek chic. Bookcases on one side and a life science mural on the other. And, weirdly, racks of test tubes on the way to the loos.
Yes, but it it art? You decide.
Dear Mr Stewart,
Thank you for taking the trouble to reply to explain your position.
However, I’m afraid that I continue to have serious reservations about the impact of the NHS bill. I refer you to this analysis
(PDF), published recently in the British Medical Journal, which identifies the key threats to the founding principles of the health service.
I appreciate what you say in your email about the historical opposition of the medical profession to the establishment of the NHS but think we have to be a bit more sophisticated in our reading of history. The NHS is now over 65 years old and so, private practice notwithstanding (this is a free country) many UK-trained doctors will have chosen their profession precisely because they are driven by the desire to contribute to a publicly funded system that is largely free at the point of use. I think we can therefore take heed of some medical opinion on the matter and the opposition of the BMA and other bodies cannot be easily discounted.
According to my reading of the BMJ article, the major causes for concern are that the bill fails to make clear who is ultimately responsible for people’s health services, and it creates new powers for charging for services that are currently free at point of delivery.
The government has been unable to show that these particular changes are vital. Of course in any large public sector organisation there needs to be constant review of performance. But this bill does not convince. Indeed it even provides scope for greater confusion over the precise responsibilities of the NHS (or CCGs) and local authories, which has long been a difficult interface; this can only be a source of increased inefficiency.
The current ‘duty’ of the secretary of state for health to provide services to meet reasonable requirements is to be transferred to the new Clinical Commissioning Groups, whose responsibilities are less clearly defined. This change will allow the reduction in government funded health services as a consequence of decisions made independently of the secretary of state by a range of bodies.
Nor, finally, does the government have a democratic mandate for this excavation of the founding principles of the NHS.