(Part 3;continued over from EF 70-200 f/2.8L vs 70-200L f/4. Part 2) Beware of fogging with the f/2.8L zoom. At the risk of getting into trouble with the powers that be, I must confess that through the years, I've noticed that several samples of the f/2.8L zoom (including mine) begin "fogging" in certain central lens elements. This fogging looks like a very fine patch of light cream coloured mist which can be detected if you hold your lens up to the light at a certain angle or shine a torch through the lens. It is different from fungus. Some of these lenses are already fogged up out of the factory while others seem to develop it through the years. I have yet to see any f/4L zooms with such fogged-up elements but then again, it's a relatively new lens. I have a nagging suspicion that certain elements in the f/2.8L zoom tend to either discolour or fog through time. It certainly does not affect all units, but I've seen a few with this problem. I've seen some samples which had fine bubbles in certain elements. Canon may tell you that these symptoms will not degrade optical quality and I tend to agree if it's only tiny bubbles and not too many of them. However, depending on its severity, fogged lens elements WILL aggravate flare and will reduce image contrast when photographing contre-jour scenes.Front-lit subjects are usually not affected though. Canon will replace fogged lens elements at a price or perhaps FOC if it's under warranty, but there is always a risk that the optical alignment of the zoom lens may be affected once it is dismantled and a new element is inserted. I have compared two similar L lenses and the one with fogged elements exhibited lower contrast, noticeable even through the viewfinder. If you're buying the f/2.8L zoom, check for lens fogging and quickly return it if your unit has it. In contrast, I have yet to see an EF28-70 f/2.8L develop lens fogging. I must also add that I have seen this phenomena in the EF17-35L and EF135L f/2 lenses. Please realise that my intention is not to start a panic or make you lose confidence in Canon. I honestly believe that this fogging issue is certainly more of an exception than the general rule...however, I have noticed it more than once and it pays to be cautious. _______________________________________ Bokeh Besides resolution and contrast, more and more people are realising the importance of "bokeh" or the quality of the out-of-focus zones. Lenses which deliver a cleaner, smoother blurred-out background can give the impression that the in-focus zone seems sharper and provide a more 3-dimensional look to the subject. It is also less distracting. Which lens has better bokeh? Without a doubt - the f/2.8L wins hands down. Not only does it have a larger aperture which makes it capable of rendering that extra bit of additional background blur, the quality of the out-of-focus areas are more pleasing. The bokeh is very smooth and clean, whereas the bokeh of the f/4L (especially closed down)can appear rather smudged and distracting. Now, let me stress that the quality of the background blur depends on the background and its illumination. A flat field of evenly lit green grass will be nicely blurred out with almost any lens. However a tangled bush with brightly coloured flowers under harsh dappled lighting can be a nightmare with lenses of poor bokeh. Honestly, the bokeh of the f/4L is not too bad, certainly much better than that rendered by the EF100 macro f/2.8 USM which I consider simply ghastly! However the f/2.8L zoom provides a quality of background blur which is smoother and much more pleasing. If you're deciding between either lens for portraiture and the quality of background blur is important to you, may I suggest you seriously consider the f/2.8L. The f/4L isn't too bad, but pay more attention to messy backgrounds should you use it. ____________________________________ In the Field If your technique is perfect, I dare say you'd be truly hard pressed to see any difference in sharpness between these two L zooms. Honestly, they are that close! However, in actual use, I was shocked to note that my handheld shots from the f/2.8L zoom were consistently sharper and more crisp compared to those from the f/4L. I was very surprised as my meticulous tests had revealed both lenses to be extremely close in optical performance. I soon discovered that I was getting poorer results from the f/4L zoom not because it was a lousy lens, but simply because it was just too light and did not balance well on my heavy Eos 1V. You need a certain amount of mass to stabilise a tele lens and the 705gm f/4L zoom was just too light for stable handholding. (Of course, your mileage will vary). The f/2.8L at 1.3kg is slightly over the top and may prove a bit strenuous for long shoots, but for me, it provides near perfect balance when coupled to the 1V. If you use an Eos Elan 7/ 33 or Rebel series camera, the f/4L version may provide better balance. In order to maximise the capabilities of the f/4L, you need a tripod, but herein lies the problem - the darn lens does not come with a tripod collar! Try shooting vertical portraits with your heavy Eos 1V tilted over the axis of the tripod ball head and you'll quickly understand my frustration. If you want this lens - get the tripod collar or else don't don't be too quick to dismiss its performance if you handhold it. Funny isn't it? You'd most probably want this lens for its light weight and use it at times when you go travelling or don't want the hassle of lugging a tripod. It is exactly during such moments that you may find it difficult to maximise its optical potential. Well, just try to keep it as steady as you can. Both lenses can be used with either EF1.4x or EF2x converters. Optical performance is still very good with the 1.4x and quite acceptable with the 2x. Stopping down will improve contrast and resolution. If you plan on using converters, the f/2.8L will have an edge as you'll still be able to employ 45-point focusing (although Canon does not recommend it) versus single point AF with the f/4L with 2x with the 1V or 3. AF slows down tremendously for both lenses when attached to the 2X converter. _________________________________ Which to buy? The choice is yours. Optically, both lenses are close...very close. They are of professional quality and in the right hands, will deliver impressive results even when used wide open at all focal lenghts. Of course, closed down a stop or two, these lenses reach their optimal optical performance. If sharpness is all that matters to you - toss a coin - both will suffice. If you need that f/2.8 aperture, the choice is clear. The f/2.8L is better for low light photography and sports, balances better for hand-held shooting, has better bokeh and a lovely tripod collar. It is also more versatile with converters. Just avoid the occasional unit with fogged lens elements, especially when buying used! The f/4L zoom is useful for those who hardly have any need for f/2.8 and simply desire a lightweight, relatively compact, high-performing optic. This is the one to go hiking, cycling or trekking with. Long walks with the heavy f/2.8L is a real pain and for those who still want to ramain standing and take pictures upon conquering that freezing summit, the 70-200 f/4L is Godsent. If you get this lens, do yourself a favour and purchase that overpriced tripod collar. Life's much easier that way. As for me, I finally sold off my f/4L and got the Leica VE 80-200 f/4 which mates to my 1V via a custom-made adapter. I lose AF and it's only stopped-down metering. But the lens delivers exquisite colour, contrast and resolution, has good bokeh (although I still think the f/2.8L is better)and is almost totally free from flare. Weighing in at 1kg, it also balances very well with the 1V. It's a lens I use when I'm taking it slow, but when the shooting gets fast and furious, out comes the f/2.8L. The only thing I dislike about the f/2.8L is its size and excessive weight. Which one is best for you? Only you can tell. Warm regards, Jonathan Kwok END * **** ******* *********************************************************** * For list instructions, including unsubscribe, see: * http://www.a1.nl/phomepag/markerink/eos_list.htm ***********************************************************
