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#41
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Sigma highlights another problem with plastics, thermal change
nospam wrote:
In article , Chris Malcolm wrote: If as was claimed more than half Sigma's lenses are bad, then a random sample (e.g. me and friends) of 8 Sigma lenses which are ok is probabilistically better than 8 heads in a row when spinning a coin. That's enough to make one wonder whether there is some trickery going on, enough to make one question whether the original claim about Sigma unreliability and inconsistency was correct. Not enough to refute it of course. It's possible to spin 8 heads in a row by lucky chance. Just pretty unlikely. how did you test them? Wide angle lenses, so I did my usual specific tests of gravel beaches, grass lawns with tape measures laid out on them, gravel beaches, brick walls, and examined the results carefully with side to side, top to bottom, edge to centre pixel peeping comparisons. I was surprised how good they were at f8, I'd have been happy at the price if they'd been worse. Especially the 8-16mm, which was noticeably sharper at f5.6 than at f8, one of the signs of a rather good lens. One thing I quickly discovered is that wide angle lenses for various technical reasons I don't fully understand autofocus poorly with at least some cameras, including mine, which has given some of these lenses an undeservedly poor reputation. I always manually focus them. Which for most shots simply means carefully finding a good hyperfocal setting and leaving it there. And I always examine the results of any good shot carefully at pixel level in difficult or critical areas. That sometimes gives me clues about new aspects of lens or camera performance. It also sometimes alerts me to unsuspected damage such as slight decentering. -- Chris Malcolm |
#42
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Sigma highlights another problem with plastics, thermal change
nospam wrote:
In article , Chris Malcolm wrote: If Sigma lenses are as bad as they say, I'm surprised that none of the Sigma lenses I have or are owned and much appreciated by several of my local photographer friends have given us any problems. That good luck should have stretched so far if most Sigmas are crap seems stretching luck and probability rather far. I note when reading lens reviews that some Sigma lenses seem to have been notoriously troublesome, while some others seem to be well regarded for build, optical quality, and consistency. I wonder, could it possibly be the case that some Sigma lenses are good and some are bad, and you can find out which are which by checking reviews etc? Could it possibly be that lensrentals have fallen out with Sigma over some service issues and are trying to get their own back? What other lens rental agencies report similar problems? sometimes you can get a decent sigma lens but it's a crap shoot. the reality is that most people don't care. they buy sigma because it's cheap and they're happy. very, very few people pixel peep or take pictures of test charts to see if their lens is functioning properly. if their photos look reasonably good, then as far as they're concerned, the lens works fine. True, but I'm not one of those people, nor are my serious photographer friends. That's why I'm surprised none of us have had these notorious Sigma problems. Mind you, none of us were foolish enough to buy one of the kinds of Sigma lenses which do have well documented problems with our particular camera, e.g. in my case the stronger autofocus motors in newer DSLRs quickly wearing out the gears in a couple of old Sigma models which were obviously designed to cope only with the earlier slower autofocus motors. While we're on this topic of specific lens models rather than good or bad manufacturers, there are some really bad cheap Samyang lenses out there. And there are also some extraordinarily good ones. -- Chris Malcolm |
#43
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Sigma highlights another problem with plastics, thermal change
In article , Chris Malcolm
wrote: the reality is that most people don't care. they buy sigma because it's cheap and they're happy. very, very few people pixel peep or take pictures of test charts to see if their lens is functioning properly. if their photos look reasonably good, then as far as they're concerned, the lens works fine. True, but I'm not one of those people, nor are my serious photographer friends. That's why I'm surprised none of us have had these notorious Sigma problems. Mind you, none of us were foolish enough to buy one of the kinds of Sigma lenses which do have well documented problems with our particular camera, e.g. in my case the stronger autofocus motors in newer DSLRs quickly wearing out the gears in a couple of old Sigma models which were obviously designed to cope only with the earlier slower autofocus motors. a problem that pretty much only happened to sigma. how often do you hear of stripped gears with nikon or canon lenses, even with older lenses that predate the high power focus motors? |
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