View Full Version : Sigma 150-500 with 20mm Ext.
11th of April 2009 (Sat), 19:37
Saw someone on the list was using this technique and gave it a try on the Hummers .... I am happy with the results. this was at 500mm.
12th of April 2009 (Sun), 03:30
Can I ask what the 20mm Ext gives you ?
Very nice shot btw.
12th of April 2009 (Sun), 03:46
If I understand the title, he has added an extension tube of some sorts, reducing the minimum focusing distance.
I'd be happy with that shot, nice one.
12th of April 2009 (Sun), 07:24
I used my Kenko tubes with the Bigma many times, and on Hummers too. Kenko tubes magnify the image hitting the sensor by moving the rear of the lens further away from the sensor, so when the image hits the sensor, it is bigger, giving an "apparent" magnification, without the disadvantage of glass in the way. Also, using tubes gives magnification without adding any f/stops, so your lens will keep auto focus. The only down side is, it changes the physics of the lens so that you lose the ability to focus to infinity. The Kenkos come in three sizes, 12mm, 20mm and 36mm, and you can stack them all if you want. Really useful with Macro lenses, but also turns that Bigma into a stand off Macro. You can fill the frame with a butterfly from 12 feet. :)
12th of April 2009 (Sun), 08:54
I use a 20mm tube with my 500mm f/4 and 1.4x to fill most of the frame with a hummer at about 10 to 12 feet. This is a couple feet less that the minimum focus distance the lens can normally shoot at.
While there is a slight magnification of the image using an extension tube the longer the lens the less the magnificantion there is. 68mm of tubes on a 100mm lens will roughly double the image on the sensor, 20mm on a 500mm is maybe in the 5% to 6% range of increased magnification if doing the math in my head is correct.
The main thing though is to reduce the minimum focus distance and fill the frame with more of the subject. Using the 20mm on my lens is a good trade off when shooting in my backyard, I have a focus range then of about 9-10 feet to about 80-90 feet which covers more than everything I may want to point the lens at in that area.
The hummer is a nice shot, look like your focus point was on the wing base. One thing to remember is that shooting this close with long glass is very much like shooting macro, the dof is very very narrow.
If you were to run your settings through a dof calculator you may well find you only have a dof of a couple millimeters, so finding the eye under the focus point can be the make or break point of a really good to a really great shot.
Shooting these birds with this technique is a lot of fun and a real challenge, keep it up, I looking forward to see more shots.
12th of April 2009 (Sun), 13:30
Thanks for the comments ... and I agree with the focus point being off a little. I am use to shooting sports and have found that a human face is a lot easier to focus on than a tiny eye on a fast moving humming bird. I felt lucky to catch the shot ... He was in a hurry to get to the juice!
12th of April 2009 (Sun), 16:38
Much easier to get a shot if the bird doesn't have a perch, it can and will still feed, heck most flowers don't have something to perch on.
But the bird will feed for a moment, back off to check surroundings and then move in to feed some more, it is the backing off period that the shot is best captured in my experience and easier to remove any sign of the feeder from the shot. ;)
And if the feeder has several points to feed from I just toss a bit of tape over the ones that the bird might use to "hide" from the camera, they quickly become accustomed to the cameras shutter click anyway and will often come over to inspect what you are doing.
12th of April 2009 (Sun), 16:48
and will often come over to inspect what you are doing.
I hang a feeder right outside my window and shoot them from my desk inside here. I have had them buzz in here to look the room over and go back to feeding. They are very inquisitive. :)
18th of April 2009 (Sat), 07:15
Very nice capture, and great info about the extension tubes. I never knew that you could use them to get closer, with a super tele. I need to get one for my 150-500.
18th of April 2009 (Sat), 08:22
Excellent shot. I may have to revisit my thinking on the Sigma...very clear and sharp.
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