Crazy Lens Stuff. Wide Open and Up Close.

I met my friend, Anne, for coffee last week at my favorite coffee shop, Caffe Medici. Out of native silliness I pulled out my camera and made a cursory shot, from a high angle, of my cappuccino and a luscious chocolate croissant. It was a throw away image. Something I might look at for a few seconds before I re-formatted my memory card in preparation for something else.

Anne looked at the image on the back of the camera and then gave me a wry look. "Really?" she asked. "That's all you've got?"

A bit ashamed at being caught in full on hipster photographer mode I sheepishly grabbed the camera again, set the lens at it's widest aperture, focused at the closest focusing distance and pulled out the LCD screen so I could shoot at a much lower angle than I usually do. I snapped a series of three images and then we put the camera away and had a nice chat.

I didn't shoot much else during the day and when I got home I took a look at the images. I was about to erase them but I stopped and took an extra couple of minutes and put them on my desktop.  I took a good look at the images and, like the nerd I am, started blowing them up on the screen to see what a lens really does do when pressed into its worst case scenarios.

And that triggered a whole train of thought for me about why we buy the lenses we do and what misguided metrics we use to make our selections.

When we look at lens tests we look at measurements that are made of a flat target but I rarely find, in real life, that I have a lot of call to photograph flat objects. When I do need to photograph flat objects I can easily reach for a macro lens that was make to photograph flat objects. But most of the stuff I photograph is three dimensional. This cup shot is an example of "real world." No matter how potentially sharp the edges or corners of the Sony 50mm 1.4 might be at its widest aperture, for the most part we'll never see the potential realized because the limited depth of field combined with the three dimensional nature of most scenes negates our ability to see those imagined results.

At the center point of this image, which is the same as the focal point, the image is generally sharp. Outside of this narrow boundary the sharpness and resolution of the outlying areas becomes immaterial.

This is the bane of most lens buyers. We don't have the ability to model accurately the critical factors of a lens in a meaningful way so we trust sites like SLRgear.com and PhotoZone.de and even DXO for their OCD testing of the lenses in which we might be interested. We also treat lenses as totally separate, stand alone tools instead of understanding their real role as integrated parts of complex imaging systems.

I suggest that we actually shoot lenses in the manner we will normally use the lens and make our choices on the merits of the lens in actual use. How does the image look compared to your initial intentions.

So, with all of this in mind I was in a vulnerable state when I made yet another fateful trip to the lens monger here in town, late yesterday afternoon.

Long story shortened, I bought a lens yesterday. It was an interesting buying adventure for me. I've been stalking this particular lens for a while. I am captivated with wide ranging, normal zoom lenses lately. I bought the much vaunted 24-70mm f2.8 Zeiss lens recently, tested it and returned it. Why? Well, the reason to buy the lens, for me, is the performance of the center part of the lens.  The people part. I don't shoot architecture and I'm not so concerned about corners and edges but I do like a sharp, very sharp inner core. I thought the 24-70mm CZ would be a big step up from the "interim" lens I bought back in early December for a PR job. It was the Tamron 28-75mm 2.8 SP lens for Sony. When I shot the two lenses side by side I found that the Tamrom was at least as good in the parameters I found to be important: Core Sharpness and Good Contrast near wide open. At f4 both lenses were good. Equally good. Why drop another $2000 on a lens that was no better than the lens I had in my hands? Not much. Back went the CZ (always keep your boxes until you are certain).

While my friends are much more impressed by the big Zeiss lens my wallet and my financial advisor are much more impressed with my pragmatic assessment of relative quality.

While I liked the idea of the extra reach of the lens I really wished for another 20mm or so on the long side of the Tamron and I really would have welcomed 24mm on the short end. My biggest beef with the CZ 24-70mm is also the very limited range of focal lengths. Shorter on the long end is even worse for me. Something like a 24-85mm makes a lot more sense in actual PR and event shooting. Even more length would be better.

So, back to the lens I've been stalking since I adopted the Sony Alpha system. It's been discontinued since 2008.  It's a rebadged Minolta lens. It's the 24-105mm f3.5 to 4.5. It's much smaller than either of the two lenses I mention above, in fact it's probably smaller than the Sigma 50mm 1.4. In fact, I'm certain it is.

I looked at it and rejected it back in December in favor of the faster Tamron lens but yesterday I looked at it one more time. But why?

At times I can be a sucker for "finder image."  When I put the small zoom on the a99 in the store and carefully set the camera's diopter I found myself liking the image in the finder. Really liking the finder image. I had two lenses in front of me. One was the Carl Zeiss 85mm 1.4 for the Sony and the other one was the 24-105mm 3.5/4.5. I pulled the 85 up to my eye and focused on some boxes about ten feet from me with the lens wide open. The type on the box wasn't particularly out of focus but it sure wasn't sharp. I chalked it up to AF focus error so I switched to MF and magnified the frame to fine focus. And it still wasn't sharp. Not critically sharp.

I started stopping down and checking and right at 2.8 I started to get succinct, sharp type in the center of the frame. I switched lenses and AF'd on the box again from the same position. The zoom rendered the type much more sharply. Wide open. I tried it at various focal lengths. Same results.

Stopping down one stop gave me excellent sharpness.

I tried the test again with the Sigma 50mm 1.4 for the Sony. It could match the sharpness of the zoom, in the center of the frame at around f2.8 as well. I wasn't seeing focus shift as I was focusing stopped down and using MF with magnification.

Since the zoom had been discontinued four years earlier and had been a shop demo for a long time I was able to negotiate an advantageous price and I bought it.

What does all this prove, if anything? That we tend to overlook many good, medium aperture lenses because they lack sex appeal but, in fact, are very, very good. Many people swear by super fast lenses but I find that they don't really deliver incredible performance at their widest apertures. My take is that our penchant for super fast lenses is based on two ideas, one of which is deeply flawed and the other was made irrelevant by our almost ubiquitous dependance on auto focus technologies.

First of all I think that super fast lenses became popular in the 1960's, 1970's through the 1980's because back then people mostly manually focused their lenses in SLRs and the faster aperture meant more focusing accuracy on the screen. The more limited depth of field also helped us get to sharp more quickly. Now that all our cameras are AF these parameters are rendered more or lens meaningless and further impaired in designs that exhibit focus shift upon stopping down.

The second parameter that comes into play is something that Erwin Puts talks about a lot. It is (according to Puts, a Leica expert) eight time harder to accurately make a lens element that is twice as large. Each increase of one stop makes the chances of creating a great optic eight times harder, times the number of elements in a lens. EIGHT times TIMES the number of lens elements.

I first noticed that some lenses that performed very well were slower than the lenses that were most popular or most used. For instance, I would say that in many regards that the Nikkor 55 Micro f3.5 is a sharper lens at f3.5 to f11 than just about any of the much pricier fast lenses on the market. Recently I purchased a Sony 85mm 2.8 lens and my results mirror those I've read in review sites. The lens is very sharp wide open. So sharp it can excite aliasing even wide open. Amazingly sharp. You hear similar stories about the older Contax 85mm 2.8 as well.

In my experiences with 85mm lenses the two Sony 85's tell the story. The big, expensive 1.4 lens is impressive to look at and impressive to look through. But it's hard to get sharp performance wide open due to the vagaries of AF and the added struggle with focus shift as one stops down. By 2.8 the lens is critically sharp (according to most tests) but then it is just on par with its much slower sibling. The 85mm 2.8 matches (to my eye) the performance of the bigger lens from 2.8 up to the diffraction limits of both lenses.

But the real thing a long term photographer should ask about the tools is, "is ultra narrow depth of field something I'll use a lot?" And then weigh that against, well, weight and price. I find most controlled shoots with longer lenses take place between f2.8 and f8.0. With a full frame camera an f1.4 aperture gives one such a narrow slice of sharpness that it becomes schtick.

Given a choice these days I would rather have a lens that's critically sharp but a little slower than a prestige lens that really only delivers when stopped down. In an odd twist the users of smaller formats may have an advantage when it comes to buying smaller, faster lenses (such as the Olympus 75mm f1.8 I talked about last week) because they use smaller diameter lens elements that can be more accurately machined and polished than optics made for larger circles of view...

So, how is the "new to me" little zoom? Where I use it, at f4 to f8, usually making portraits, I find it to be a fine lens and one perfectly suited for events. Is it so sharp it will call attention to its sharpness? No. But it's a nicely rounded sharpness that seems to work well for people. It's better on the a99 than on the a77 and I chalk that up to the interaction between the resolution limits of the lens and the resolution density of the two digital imaging sensors.

I'm heading out the door to shoot with the smaller lens right now. For a little while it will join the Tamron 28-75 and the Minolta 24-85mm in the equipment drawer. I'm putting them all through their paces right now and the winner will get to stay while the other two will be sent packing. Right now it's neck and neck between the Tamron and the Sony. More to come.

added later in the evening: And the early returns are good. The 24-105 has a unique look to it. Sharp but roundy..... I'll post a few and then we'll test later, in depth...