Friday, February 27, 2009

Lens reviews/ Chromatic Aberration

One of the most awesome aspects of the  1Ds Mark III and the new 5 D Mark II is the fact that the resolution of the new cameras actually outstrips the performance of (some ) older Canon L series lenses. This is why there have been so many new " II " series additions to the Canon lens line.

Chromatic aberration in particular was never a huge problem in the past when a print from a 35mm negative was seldom enlarged past 11 X 14.  We just never looked at stuff with that kind of magnification.

Now I check almost every image I submit at 100%.  Why?  Because the client probably will.

I just sent some photos to a designer who called back wondering why there was a little red/green fringing on an image, even though the photo was slated to be used on a website at about 5 X 7 at 72 dpi.  People are really picky about digital images.

Given the amazing low light abilities of the Mark II,  I've been  daydreaming about buying a really stupid fast lens, but the 24mm f 1.4 (just upgraded) is almost $ 1700, so I wondered if there were any bargains to be had that were really good from secondary suppliers like Sigma or Zeiss.  

I came across this great website, The that has the most extensive and in depth lens reviews I have found. Unfortunately he only reviews Canon related gear but I always check it when I am looking to buy a new lens.  Alas, there are no bargains in the fast wide angle category, but it did save me from buying a Sigma 24 or a Canon 28 mm 1.8 that I am sure I would have been disappointed with.  However the tests do show that are some really outstanding lenses for Canon cameras that are real bargains, like the 85 F 1.8, the 100mm F 2.0, and the very surprising 18-200 and 10-22 EF-S lenses. 

So what is Chromatic Aberration and why is it suddenly such a big deal?

The easy answer is that it's just the inability of the lens to focus all of the wavelengths of visible light to the same point.  However with digital imaging there are more things to consider:

When photographers shot color film the different colors were recorded on different layers so lenses could actually be optimized to take advantage of the slightly different focal planes for each color layer.   Film had a certain amount of physical depth that lens designers could use.  However a digital sensor is a truly flat plane, so CA is more noticeable.  We also shoot a lot more with zoom lenses, and it's tough to correct a zoom lens so that it performs perfectly throughout the range.  Smaller chips also mean shorter focal lengths and CA is much more of a problem in short focal length lenses.

Finally, the imaging sensors in digital cameras also have micro lenses on each photosite in the chip itself.  These small micro lenses introduce another form of CA because they are tuned to more accurately focus green wavelengths, at the expense of red and blue wavelengths (perhaps because it's the midpoint in the spectrum?) and this can result in purple fringing.

I've actually accentuated the CA in this photo to make it easier to see.

CA is also more visible in digital images because the digital sensors responds better to light rays that hit the focal plane perpendicularly.  Film didn't care.  When you add it all up it is easy to see why Canon has been revamping their L series lens line.  The old lenses were optimized for film and all of the new lenses are marked by less CA when used for digital capture.

While it is possible to mitigate the effects of CA in Lightroom and Camera RAW, it doesn't always work perfectly and it is really time consuming, so good lenses are still the most important factor to overall image quality.

One other interesting side note:  Like almost everyone else I use skylight filters on my lenses to protect them.  I recently replaced the $ 20 Sunpack filter on my 17-40 mm lens with a primo, $ 100 Rodenstock skylight filter.  The very small amount of CA that lens had was virtually eliminated by simply upgrading the filter, and lens flare was also reduced to a negligible amount.   It was really worth the extra cash.

I might start a Rodenstock dealership.  Maybe then I 'll be able to afford the $1700 24mm L series II.

By the way, there's a nifty little tool in Lightroom 2 that can help with any residual CA you can't fix with the Chromatic Aberration sliders:  Grab the paintbrush tool and just de-saturate the edges.  

Thursday, February 5, 2009

Living with the 5D Mark II

So yes. It is all that. Quite simply the most capable, best camera I have ever used. The files are as close to perfection as I have seen from a digital camera that was less than $ 40,000. I tested it against the 28 MP Leaf back and preferred the Canon images (which I think had more to do with the Canon lenses vs. the Mamiya lenses).

So should everyone run out and buy one?

Sorry, but if you are not paying your rent as a photographer it is complete overkill. The fact is that I've only had one job in the past three years that required this kind of resolution ( I rented a 1Ds Mark III). It's better than medium format 6 X 7, not quite 4 X 5, but I'm not selling my view cameras or my Mamiya 7. Film still rules on many levels.

The best part of the new 5D is not the resolution, or the video, it's the lack of digital noise. Visible noise levels at ISO 800 are about the same as my 40D at 100! When you combine it with the advanced noise controls of Lightroom 2 you have a camera that changes all your thoughts about shooting in available light. Absolutely stunning. I do get a teeny bit of pixelation if my exposure isn't perfect at ISO's over 1200. As always, it's best to expose a bit to the right (ETR), especially in low light conditions. In my casual photography I set the camera to sRAW (10MP) to take advantage of the reduced noise, but save the space on my card and hard drives.

The new 50D has the same Digic 4 processor as the 5D Mark II, it has 15 MP native resolution with a smaller APS sized chip. so the noise levels should be very similar, if not identical to the 5D Mark II. It's also almost half the money for a camera that should be capable of producing a spectacular 30 X 40 print (assuming careful processing of RAW files). Remember that resolution is measured linearly, so the jump from 15 to 21 Mp is only about 12 percent. If you aren't a working pro, then save the cash and buy an L series lens with the savings. Every time I test a new camera system the lens quality is always the single most important item in the equation, with noise running a close second. Given the choice to shoot a 10 MP 40D with a primo lens or a 5D mark II with a sub par lens I 'd actually take the smaller camera with the better lens.

But wait! What about HD video on a full chip camera? Hasn't that been the Holy Grail for videographers? Beautiful bokeh that takes advantage of longer focal lengths and bigger lens openings; HD that looks like it has the production value of a Hollywood feature?

The 5D Mark II delivers as promised, but here's the fine print: You have to shoot it like you are a professional cinematographer. That means tripods and fluid heads, assistants to pull focus, dollies or steadycam for tracking shots. If you aren't using an IS lens there is no steady shot to help you, and the camera won't auto focus when shooting video (actually it will, if you press the AF button, but the aperture opens up to admit more light and will ruin a shot with a few seconds of overexposure). Pulling focus smoothly on a tripod is tough, and almost impossible on a small handheld camera without a brace. Besides, the video only works in Live View so you are pulling focus while looking at a small video
screen; not optimal.

In order to get the most out of it you need to treat like its' a 16 mm Arriflex. Here's rig from Redrock that does exactly that. Yes, that's a Canon 5D on the back end.

Then there's the sound issue. Forget the built in mike, it's right next to the lens and picks up all the noise your hands make while working the controls. My solution was to adapt a Stroboframe flash bracket so I could mount a shotgun mike. Finally, there is no output jack to monitor the sound while you're shooting. If I were shooting something that was really dependent on great sound I'd probably add a separate wave recorder and a boom mike into the equation, Again, just like a real film maker.

For all of you who were blown away by Vincent Laforet's "Reverie" (shot on a 5D mkII), look at that film again and you will realize that while it looks great, it is also shot in a style that maximizes the good qualities of the camera and minimizes the problems. It's essentially a series of still photographs. This isn't a camera for shooting documentaries.

So yes, am I happy, but given my immediate needs, I might have been better off with a 50D and an $ 800 Vixia HD camera. For the average student, photojournalist, or prosumer this would probably be the better option. The 5D will be perfect for a short film I'm going to make in a few months for the same motorcycle I shot in this post. It excels at MOS beauty shots, so as long as I add a cute little Vixia for pickup shots I should be in great shape.

The thing that's interesting is that the 5D has been banned from Formula 1 racing events and World Cup Soccer. Why? Because TV and film producers pay for the rights to shoot at those events. The 5 D Mark II enables anyone to produce broadcast quality video. I will be really bummed if I am banned from shooting stills at motorcycle races this season because I am working with a hybrid camera.

This is what I see on the horizon, (imagine a future 1Ds Mark IV): In my camera collection I have a very unique camera from the 70's made by Canon, the Canon Pellix. It was a specialty camera for sports photographers with semi-silvered (pellicle)mirror that didn't move. The light was transmitted through the mirror so there was no blackout at the moment of exposure. Why not incorporate a pellicle mirror into a digital camera? That way you could still use the cameras finder instead of the screen on the back. Add a couple of zoom lenses with power zoom capability, a headphone jack, 24 FPS capture rate, and you would truly have a hybrid video/DSLR!