Lensblogger

The myth of UV filters

I hear it daily. "Always protected by a UV filter" in the for sale adds. "UV filter saved my lens." Etc. It seems people are terrified they might actually take a photograph on a lens that doesn't have a UV filter on it. And absolutely for certain when you buy a lens the salesman (online or in store) makes you feel like you just crawled out from under a rock if you don't buy a UV filter to protect your investment.
Lets get the last part out of the way first: if you aren't aware, UV filters are among the highest profit margin items in most camera stores. The store often makes more selling the filter than they did selling the lens (lenses are a cutthroat business with very little markup). I buy filters in bulk and pay less than half of camera store prices so I know the profit margin is at least 50% for them, more at the huge stores. Lens markup is often 5% at most. So EVERY camera store and salesman is going to try to sell you the filter. That's where the money is.
Lets get the second part out of the way: UV filters prevent fingerprints, wet spray, and blowing sand and grit from impacting the front element. They protect THE COATING ON THE FRONT ELEMENT. That's all (except possibly a few Canon lenses that are reported to have a complete seal only with a filter in place like the 17-55 f2.8 IS). They don't protect the glass from shattering (actually, filters which are soft glass are more likely to shatter and scratch the front element). They don't protect the lens from breaking if its dropped (a lens hood may if its not a wide angle lens, a filter doesn't). And if a lens drops 5 feet and doesn't appear damaged - well I'd check my calibration pretty carefully if I were you.
And here's where the myth really gets busted: You're not using a filter to protect a $1,800 lens. You're using it to protect a $300 front element. It changes the math considerably. Plus you can't use that cheap $25 UV filter - that's going to get a major drop in image quality. Why pay $1200 for a lens and then ruin the image quality with a cheap filter? Very good multicoated filters have little (not none, little) effect on image quality, but a good 77mm filter will run $70-90 dollars). So now we're spending $80 to protect a $300 front element. And filters, being soft glass, not the tempered glass of a front element aren't going to last as long as a lens, so they'll end up needing replacement every couple of years.
Here's the quick math from Lensrentals.com. Over 700 lenses were rented for a total of 16,000 weeks of use (heavy use) resulted in 6 damaged front elements in the last year. Cost to replace front elements was $2,255. Cost of 700 UV filters at wholesale $28,000 for a decent, not great, filter (your cost would be higher per filter, we can buy by the gross).  So if we spent $28,000 for filters we would have saved $2,255 in repairs (and this assumes it would have prevented all 6 damage incidents which is unlikely). Does this apply to the individual? Sure. If you buy filters for 5 nice lenses it should cost you at least $275. And it might save you a $350 front element repair someday. Would you pay $275 an insurance policy that covered a maximum benefit of $350? Me neither.

Reflex (mirror) Lenses Revisted

Since I started in photography, reflex mirror lenses were 'fools gold'. Most new photographers nibble at them, usually getting steered away by more experienced photographers. But it sounds great: a 500mm lens for a few hundred dollars that's small enough to throw in your camera bag. Mirror lenses actually have one real quality advantage: because the light is reflected from the mirror, rather than refracted through glass, they have no chromatic aberration.

But there's a reason people carry around those 3 foot long, 10 pound 500 f4 lenses. Mirrors are usually f8 aperture making them too slow to get any action shots, and given the long exposure times f8 requires in all but the best light, you still need a tripod even for that little bitty lens. Plus the out of focus highlights are a rather unpleasing doughnut shaped light ring.

I recently shot with the Sony 500mm f8 reflex on the alpha 350. My thinking was that the in body Image Stabilization of the Sony SLR might make the lens usable without a tripod. But I wasn't really optimistic. After shooting around a bit I have to say I was pleasantly surprised. The lens is decently sharp as shown here and I found I can handhold it quite easily at shutter speeds of 1/500 (you may do better, I've got a pretty good caffeine tremor going on, but for me this was excellent).

The out of focus highlights are still the not too pleasing doughnut shapes you can see in this shot. But you can't have everything. Bottom line is this gives me an opportunity to carry a long telephoto lens around when I'm not absolutely planning on using it, say for a hiking trip. Its not going to replace a 500 f4 for a dedicated bird or wildlife shoot, but its still a very nice option to have.

First take on the Sony Alpha System

Lensrentals.com has decided to take a big plunge and start stocking Sony alpha SLR equipment. From a pure business standpoint it doesn't make a lot of sense: there just aren't enough Sony owners to support it . . . yet. But the system seems to have a lot of promise and I was pretty curious so we jumped in. My biggest hesitation on the sytem's eventual success isn't the equipment itself, its Sony's marketing. They push the system through big box electronics retailers and its difficult to find in camera stores. That's probably effective in capturing the "want a better camera than my point and shoot" folks moving up. As those owners get the bug, though, and want to consider better lenses and accessories, the advice they get at those retailers is going to be less than worthless. That worries me. But on to first impressions.

The body I've shot with a bit is the alpha 350. Compared to the Nikon and Canon cameras I usually shoot its better and worse. That about sums it up if you want to skip the rest.

The body itself is fairly small, just a bit bigger than an XTi or D40, smaller than a 40D or 300D. Its rather plasticky feeling and light, again like and XTi or D40. It also feels a little slick in the hand since the grip isn't very pebbled. I wonder how slick its going to feel in mid summer when I'm sweating.

The layout of controls and menus is different: more switches on the body, the rear LCD the source of all information, the menus, of course, seem foreign at first. I've pretty quickly grown to like the multiple switch layout though. Important controls are at hand with no staring through multiple menus I can't read in sunlight to find them. Its still not intuitive for me, but the control ergonomics are logical and well laid out as a whole.

I really, really like the tiltable mirror. I'm not a big live view shooter, but that's a nice feature that the other companies should emulate. It makes it much easier to see in sunlight for certain. Autofocus, white balance, autoexposure are all as accurate as the mid level cameras from Nikon and Canon, or perhaps a bit better.

Image quality is a mixed bag: There's lots of detail in the 14 Mpix images, colors are rich (the reds seem a bit oversaturated on jpgs at times, but that's probably just a setting adjustment I haven't discovered yet). Noise is more of a problem than the current Canon and Nikon cameras. I see more shadow noise than I'm used to for certain, and seems a bit more chroma noise in out of focus areas. Its fine at ISO 400 but at ISO 800 I'd definitely be using a pass through Noise Ninja or similar software. 800 is quite usable, mind you, but I've gotten spoiled shooting with D300s and 5Ds. The 350's noise level is similar to D200 or 20D cameras, so I guess Sony's about a generation behind. Or perhaps the smaller pixels on this sensor are the culprit, I haven't shot with the lower Mpix alphas to compare.

As to the $64,000 question: the in-body image stabilization works. It works really well. It works about as well as what I'm used to from lens based IS and VR on the Canon and Nikon systems. I've heard the arguments that lens based IS is superior and some of them make good sense, but for everyday shooting around, the image stabilization on the sony is excellent. And it works on prime lenses and wide angles where its not available from the other manufacturers. (Yes, I know you don't NEED it on a wide angle, but it sure is fun handholding 1/2 second exposures. Tell me you'd never, ever use that. Liar).

Lenses are somewhat limited compared to the other brands, and a bit pricier. But I've shot with half a dozen lenses now and I'm pretty impressed with all. The Zeiss 16-80 Vario Sonnar is as good as I had hoped, if a bit aperture impaired. The 50 and 100 Sony Macros are excellent, like most Macro lenses. The 50mm f1.4 is very similar to the excellent Canon or Nikon versions of that lens. I'll have more lens impressions later, for now you can download some full frame sample images from the various lenses on the Lensrentals Sony page: www.lensrentals.com/category/sony-rentals