Chromatic Aberration - Difference between f/1.4 and f/1.6 on Canon 50mm

I had read that my Canon 50mm f/1.4 lens has noticeable chromatic aberration (CA) when wide open, but was really surprised how bad it was, and how it almost entirely goes away at f/1.6.

I really love this lens - this is a minor problem to deal with, but it's nice to know to expect it.

Below are crops from two out-of-focus shots I took while driving: the first at f/1.4, the second at f/1.6. Notice the purple fringing around most of the lights at f/1.4. This is caused by different wavelengths refracting differently through the glass. I put up a full shot at f/1.4 on Flickr, here.

50mm f/1.4	50mm f/1.6

Rock & Fossil Macro Shoot: Trilobite!

Check out my Flickr page for this shot, as well as other fossils and rocks shot with this setup.

I recently received a request for permission to use this photo in a non-profit magazine on Mexican biodiversity by the conservation group, Naturalia.  This particular trilobite will be featured in an essay about extinction.

SPOILER ALERT: trilobites have recently (around 250 million years ago) become extinct.

So, let's get down to how I shot this.  

I placed the sample on a couple of sheets of printer paper.  I then taped together a ring of printer paper to surround the sample.  I used my Canon ST-E2 infrared transmitter to fire off two Canon 430EX strobes that were placed right up against the ring of paper.  The paper acted as a diffuser, which bounced soft light all about inside the ring, reducing shadows on the fossil.  All of this light let me use f/22 with my Canon 100mm macro lens, which I hand-held at 1/250sec.

Here's my personal favorite from the shoot:

Dew Drop Lens

Dew Droplet Lens, originally uploaded by blakophoto.

100mm, f/13, 1/60sec, ISO200, -1/3eV

I woke up this morning to take the dog out, and noticed how pretty the dew was in the grass. So, I put on my slippers and spend 15 minutes crouched over, trying to get this shot.

I've taken dew droplet shots before (here), but this time really wanted to use the drop as a lens, focusing on the background. I had the extra treat of being able to get the sun to shine through, and then out of the droplet.

To get this shot, I propped up my 100mm macro lens on my Canon 40D on an upside-down seed-starting tray that was conveniently nearby. This put the camera about 2 inches from the ground. I really didn't want to lay down, and I don't trust autofocus or my viewfinder to get this right, so I used Live View -- manual focusing with the LCD screen.

I knew I'd heavily crop this, so framing wasn't that important. My Canon 40D's Live View lets me pick a spot in the frame and zoom in 5X and 10X. At 10X on a 3 inch LCD screen, you'll have a pretty good gauge of what's in focus and what's not. What made this a little tricky was that the focus ring was resting on the surface, so focusing would also move the lens. To be sure I'd get the shot, I took about 10, making small adjustments to the focus each time.

I wanted to go as high as I could with the aperture to improve depth of field, and get as much of the grass in focus as possible, even though it wasn't the main subject. I had to balance that with the need to keep the shutter speed fast enough to stop any small breeze or jerk of my hand, since I wasn't using a timer to take the shot.

I decided ISO200, only because I couldn't get to ISO100 - I had enabled "higlight tone priority" a few minutes prior, and forgot that it doesn't let you below 200 for some reason. f/13 gave me 1/60sec, which I was figured would stop any breeze or incidental hand shake. This was somewhere between hand held and tripod mounted, so I could go a little slower than 1/100, but not as slow as 1/2 or so.

Looking Up Trees - Soft Corners at f/3.5

Looking Up Trees, originally uploaded by blakophoto.

17mm, f/3.5, 1/60sec, ISO100, -1/3eV

I took this while walking around a local park, testing out my new Canon 17-55mm f/2.8 IS lens with my Canon 40D body. I am completely in love with this lens. However, with this shot, I was very disappointed to see soft corners, when I knew from this DoF calculator that the whole frame should be in focus for f/3.5 and the point I focused on. The soft corners are visible at low res, obvious when zoomed in.

My first thoughts were that I had a bad copy of the lens. But, after reading, and evaluating the MTF charts for 18mm, I learned what I should have already known. Even good lenses might have a tough time with corners when wide open.

I found this great review on the lens, comparing it to several other in the focal range. Of note were the
18mm test corner shots at f/2.8 and f/5.6. At f/2.8, the corners are very soft, but at f/5.6, they're very sharp. It's interesting to then compare corner shots of this lens to the non-IS kit lens at 18mm, f/5.6 - what an improvement.

So, if I paid all this cash for the f/2.8 model, but have to use f/5.6 for shots like this, then what did I pay for? Well, it's still great for portraits and to stop motion in a pinch - it's one of the best walking around lenses you can buy for FOVCF bodies.

For portraits, f/2.8 blurs backgrounds well - but not as well as my f/1.4 50mm, and the MTF charts at 50mm heavily favor the f/1.4 50mm. So, if I'm specifically shooting portraits of one or two people, I'll probably reach in the bag for my fast 50. But, this lens will probably spend most of its time out of the bag.