Less Than an Inch of Depth of Field!?!?!?

So I recently acquired a new bird/wildlife lens.  I came across an old Canon 500mm f 4.5, non-IS in unbelievable condition for its age and I had to make it mine.  This should become my main bird lens, but I have kept the 400mm 5.6 as a backup as well as for use in specific scenarios.  I have used the 400 for three or four years and I felt I was just beginning to become proficient with it, just getting to the point where it was comfortable, like an extension of my eye.  I understood almost everything about the lens and the laws of optics shooting at this focal length on a 1.6X crop body.

I realized that switching to the 500mm would bring about a lot of change from what I was used to.  I knew I would be outside my comfort zone for quite a while, perhaps I would not be able to tap into the full extent of what this new lens would bring for a year or more.  I am prepared for this and have made sure my patience account is well funded (especially now since my monetary accounts are not) .  So far, in taking the beast out for light duty, I have been relatively pleased by the results I have been able to make.  I still have much to learn, however.  What are some of the big differences between the 400 and the 500?  First and most notably is size and weight.  I went from the 400, which weighs about 2.5lbs to the 500 that tops in around 6.5lbs!  This is not a negligible difference.  The new lens is almost twice the length of the old as well.  Also, in my opinion, the laws of optics seem to have changed more than the increase of a mere 20% the corresponding focal length.

Take this image, for example.  One expected change with this lens I knew was coming would be for the demand of light.  On this day and setting the light was quite lacking.  So, I decided to open up the aperture to the full f/4.5.  I had already determined that this lens is not like the 400 f/5.6.  In the 400, there was no need to stop down to improve sharpness and image quality.  I could shoot that forever at f/5.6 and be satisfied I would be getting top IQ.  The 500mm is a bit of a different story.  So far, it looks like stepping down the aperture will definitely increase sharpness, maxing out around 6.3-7.1.  The photos taken below f/6.3 are definitely still usable, but it is not hard to see differences.  So, the main point I am attempting to make is that what I did not realize until I got this photo on the computer is that although the bird’s head is reasonably in focus, its feet are not!  I estimate that I was about 20″ from the bird.  Looking up the DoF on an app, I discovered that the area in focus at this distance while shooting at f/4.5 was less than one inch!  Using the 400 “wide open” at f/5.6 at that distance the range was about three inches, likely enough to get this whole subject in sharp focus.

It was never my intent to discuss gear in this blog, but I fealt this transition was something I’d like to record and share with other photographers that might be considering similar choices.  This is but one of several examples of differences between these two lenses that I will need to adapt to in order to get the maximum out of each lens.  Patience and practice will be needed in ample amounts, and I am definitely looking forward to the challenge.  Happy shooting, birding, or whatever is your passion.


“Out of Focus Feet”

Technical details: Canon EOS 7D camera, EF500mm f/4.5L USM lens, ISO 800,  f/4.5, 1/250 sec

2 thoughts on “Less Than an Inch of Depth of Field!?!?!?

  1. Interesting! A few years ago, I bought the Sigma 150-500, and that was quite a learning curve. From the looks of the photo, you’re off to a great start and already capturing some great images. If I got a shot that sharp of a nuthatch’s face, I’d count it a success. Look forward to seeing what else you get with that lens.

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