Monthly Archives: June 2011

What do you mean, it’s out of focus again?!

I have a lens that I absolutely love for many of it’s qualities, but at least with our 7D when wide open it consistently misses focus by just a bit. But enough so that when shooting stacked photos of our dogs (i.e. standing in a certain way to show the structure) the dog is just barely out of focus. The ground immediately in front of the dog however is tack sharp for 20cm or so…

The lens in question is a Sigma 150/2.8 EX APO MACRO DG HSM. I really like the lens and the way it has a very shallow depth of field when wide open. But, like I said most pictures taken when wide open tend to be a tad front focusing. So while I’m not interested in the least in shooting test shots of lens charts etc. I decided to follow the microadjustment tricks by Arash Hazeghi on a bird photography forum.

After some time clicking away at the focus and generally fiddling around, based on some quick tests I dare say focusing has improved. By how much remains to be seen since it is too cloudy outside to attempt any kind of pictures of even a standing flatboat – they never stand entirely still and motion blur will destroy any attempt at evaluating sharpness ;)

Just as a note, when the subject is 7.5 metres away from the camera, with a 150mm lens on a 7D opened up to f/2.8 the depth of field is only 27 cm so the margin of error isn’t very large.

And although I wasn’t planning to, I did grab a few test shots while our grill was heating up.

At least based these quick tests, the focusing is better and spot on where I wanted it to be. Admittedly I did misfocus quite a few shots, but 150mm and a close subject means that even the slightest shake of my hand is quite large. And the flames and smoke between the lens and firewood didn’t help either.

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Shutter speed and video

In my attempts to learn about shooting and editing video I encountered a guideline that stated that for video the shutter speed should be the inverse of the frame rate. So for 25fps the shutter speed should be 1/25 s and so on. The reasoning for this is that it gives moving objects in each frame some motion blur so that motion the change from frame to frame isn’t quite as abrupt. What I read sounded and felt like good advice, but it did lead me to wonder if the same holds when the motion is very fast.

As is readily apparent I shoot a lot of pictures of fast moving four-legged objects that are often black – aka flatcoated retrievers. In my photography I’ve noticed that often even 1/250 s isn’t enough to completely freeze movement when the dogs are in full motion. So I was a bit skeptical whether the advice would apply even when shooting fast moving dogs. Or any other fast moving object for that matter. In defense of my skepticism I must admit that I didn’t doubt the advice when considering objects moving at normal speeds: human walking, normal gesturing, human running etc.

The idea for this shoot is something I’ve had for quite a while, but since I don’t have two cameras capable of shooting manual video, I had to wait for my friend Victor Jason to come over. We’ve reduced most of the variables we could to get similar enough image quality that it wouldn’t be a factor. The following videos were shot with two Canon 7Ds mounted on a single tripod. Both cameras are using a Canon EF 70-200L f/4 USM, although the baseline had the IS version. ISO speed, image styles etc. were also identical. Because we didn’t have ND filters there is a difference in aperture in addition to the shutter speed. Both cameras were also prefocused to the to the line that Topi used when running right to left. My wife Anna served as Topi’s handler and for each take he ran a “mark” – he saw the dummy being thrown and retrieved it once he was given permission. I threw each mark so that they landed in roughly the same spot every time.

We shot two sets of baselines with varying shutter speeds. The first video is shot at 720p with 50fps and the second at 1080p with 25fps.

Shutter speed test at 50fps from Ramin Miraftabi on Vimeo.

Shutter speed test at 25fps from Ramin Miraftabi on Vimeo.

I added the 50% slow motions just to help in seeing what the differences are with the various shutter speeds since Topi is mostly moving too fast. But the idea was to get him moving across a fairly limited field of view to maximize the amount of movement between each frame and we didn’t have any reliable gear or enough experience to seriously consider panning.

Before I discuss my own observations, here are three screen captures from the 1080p video with the shutter speeds of 1/50 s, 1/200 s and 1/1000 s. Of course in all cases the baseline 1/25 s is in the screen capture as well. BTW, note that the leading image was shot at 1/1000 s although not in the same session.

When originally editing the shots my initial impression was that there will be noticeable differences between say 1/50 s and 1/400 s. Of course this was based on looking at single frames and doing slow scrubs back and forth so the impression wasn’t exactly based on watching the actual footage. When I finally watched the rendered clips, I was surprise at how good the baselines look in both cases. Even when watching them on my 24″ monitor at too close a distance the amount of motion blur in the baseline doesn’t make the footage unacceptable to my eye.

But once I watched the edited clips over and over again I began to notice a few things. Most notably:

  • higher shutter speeds show more detail and reflection in the coat (good)
  • 1/25 s is practically a blurry blob in frame grabs (bad)
  • 1/50 s is blurry but shows more reflection in the coat (better)
  • I can’t really see significant differences between 1/200 s and 1/400 s (good)
  • In 1/1000 s the motion starts to get a bit jerky after repeated viewings (bad)

My own final conclusion is that almost anything between 1/50 s and 1/400 s goes and produces acceptable enough footage. I’ll probably tend to pick 1/200 s in in most similar situations but I’ll know that lower shutter speeds will probably be better when the motion is slower or smaller on screen. 1/25 s is much too blurry for my taste, at least with a black dog. Hmm… Maybe we should have shot a similar set with Luka after all while we were at it ;)

But I’ll be happy to say that the advice I read (sorry, I don’t remember the source) isn’t wrong but is solid advice for most scenarios. I’d love to hear what other viewers think based on these comparisons or their own experiences.

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Who gets to be a photographer?

A Finnish photographer (long-time pro) just wrote a blog entry on who gets to be a pro photographer. It’s an issue that has been discussed in blogs and books all over. In Finland there have even been some discussions on regulating the use of the title based on education like doctors’ and nurses’ titles are regulated. However, in this case a clear stance isn’t taken on who gets to call themselves a photographer or not – but some qualities that a professional photographer should have are discussed.

In a slightly opposite corner we then have David duChemin who would rather we all called ourselves photographers. As someone who has official training for the field in which he works in, I can certainly relate to the benefits of formal education when pursuing a profession. But at the same time, IT (and specifically web development) has seen so many great talents rise without any formal education that I can certainly see how formal education is no guarantee of skill or lack of it.

I agree with Matti Sulanto’s – and I presume most others – view that a professional should be able to cope with several different fields of photography and have the skills needed to produce consistent results. But just as in web development, the craft requires constant learning and challenging of oneself. When walking by most pro studio windows these days I’m appalled by the lack of creativity shown by the portraits that the photographers use to showcase their work and skills.

I don’t consider myself a pro photographer and probably never will. But I do consider myself a photographer and would like to do more work for pay in the field. But at the same time I have enough knowledge in my own strengths as a photographer that I won’t even try to take work that I don’t have the skills for.

This is a question that has no easy answer. I know my opinion – anyone should be able to call themselves a photographer and it is ultimately up to the client to decide what kind of photographer they want to use.

Maybe what is really needed – instead of the bickering who is and isn’t a photographer – is a guideline for prospective clients on what they should look for when evaluating photographers. But in the meantime clients have to go by portfolios, references, and blogs. In fact, looking at a photographers blog can be quite revealing…

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