Google Earth Depth of Field overlay

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6 Jan 2010 - 5:42 PM

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Mike Otley (e2 Member)

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6 Jan 2010 - 5:52 PM

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??????????

Why?

I used to be an aerial photographer - air-to-ground.

At 800ft (legal minimum altitude over built-up areas), using a 165mm f2.8 lens (wide open on Kodak 160ASA film) on a Pentax 6x7, shooting obliquely at anywhere between 80 and (at worst) 45degrees, Depth of Field was the last thing on my mind!!

Transfer to a Satellite.

Why is DoF an issue? There isn't any!

Or have I misunderstood something here?

LensYews

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6 Jan 2010 - 6:19 PM

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I have difficulty in applying the depth of field tables in real life at sporting event, where I'm setting up in advance of the action and then have a few seconds to capture the action.

After analysing why I wasn't getting as much of the image in focus as other photographers I found my estimated 60 feet, turned out to be 40ft when measured with the google earth ruler. If I'd I known that before hand I would have changed the settings I was using or my shooting position to get more of the action in focus as my depth of field was smaller than expected.

So I was looking for a better way to prepare for an event, as I know what route is going to be used. A depth of field overlay would be a useful tool for me to go to the event knowing what my ideal settings/shooting position would be and adjusting for the light/conditions on the day.

LensYews

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6 Jan 2010 - 7:03 PM

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Thanks Mike, its the third one of those links that've been using. I guess I need to find a way of taking it with me, I don't think my 2001 vintage 'smartphone' will load it and getting better at relating the figures to the scene in front of me.

LensYews

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12 Jan 2010 - 12:21 PM

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Let me rephrase this question as a 'best way to focus question' now that I've explored the site and put together a table of my ideal settings. I've determined that for frozen action group shots I need a depth of field of approx 30 feet.

My problem is that I have between 1 and 16 subjects travelling at between 26 and 30mph, either grouped together or spread out a little. My target area for the images is 11 meters wide by 6 meters deep (back of the fence to the landing area) and I'd like for group shots to have as much of that area in sharp focus as possible. The subjects are in the target area each for a max of 4-5 seconds (they cover 11 meters per second racing, but slow slightly for the jumps), perhaps 20 seconds for the entire field. My distance to the subject varies but is typically 20 meters, and would not be less than 8 meters (which I understand is about the maximum range of accurate autofocus tracking).

So is the best way to try and capture this action to manually focus 2 meters from the front/centre of the target area, from around 20meters, focal distance of 100mm and looking to achieve a aperture of f8 and a shutter speed of 1/1000+ (45 degree angle of shooting to subject)? Or is there a better way of freezing the action on fast moving group shots?

See this upload to the critique gallery for a photo which I feel worked, and versions of others that didn't using various focusing techniques.

(My individual shots are okay as I can reset my settings and focusing accurately enough if the race unfolds that way, and my panning skills are improving, but these aren't the type of image my customers want).

LensYews

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12 Jan 2010 - 4:53 PM

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I tried a 17-40, but couldn't get in close enough with that. I've just added a version 5 using that Lens. I tend to start at ISO/ASA 400 and go up from there, trying not to go past 1000 unless the light is very poor.

Perhaps I could use the 17-40 on a remote camera under the fence and at one or two courses, but with the majority I can't get much closer than about 10m from the action.


Quote: I think your over complicating it for yourself.

Certainly wouldn't be the first time. Just trying to work out how the other togs seem to get a much high proportion of in focus shots than me. Perhaps its not the photographer skills that need improving and its that the D300 & D3's are that much better than my 40d. But I suspect the 40d is capable of a lot more, its just working out what I don't know.

LensYews

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12 Jan 2010 - 5:10 PM

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Looking at the 1d4 white paper, the AI servo performance has a new algorithm but the range remains the same:

"As an example, with an EF 300mm f/2.8L IS USM lens, the EOS-1D Mark IV can track a subject approaching at 50 kph/31 mph up to about 8 meters/26.2 feet away. This is the same specification as the EOS-1D Mark III."

Does anyone know in practice how AI servo performs on a subject moving at the same speed, but twice as far away using a 17-40 or a 70-200 f2.8?

LensYews

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12 Jan 2010 - 5:52 PM

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Yes, I've been weighting up upgrading, and will soon have the funds to do so, and all the Canon options (1d2n, 1d3, 7d, and 1d4) have their pros and cons. Just been using the time from postponed events last weekend and this week to reflect on my current level of ability and see where I can improve. So it looks like stick with the individual shots for the moment, and revisit group shots when I have more capable equipment, but keep practicing in the meantime when I have the opportunity.