As discussed with Araminta (M-L) on another post, I am writing this here with the aim of increasing my photographic knowledge, particularly with respect to photographing birds.
If anyone (esp. Holly), thinks this is an inappropriate use of the site, please let me know.
I recently purchased some extention tubes for my DSLR. These are usually used for converting a normal lens into a macro lens. By moving the lens further from the camera, it allows the lens to focus at a shorter distance than its normal minimum.
Who among you has been frustrated while trying to snap a bird with a long lens, just to have it fly so close that you cant focus on it! This has happened to me many times. I started carrying two cameras, one with a shorter lens, just in case this happens, but I have found two cameras very arkward, and my frantic efforts to get the other camera up has so far been unsuccessful.
I have been using a Sigma 150-500mm zoom lens and I am very pleased it but it can only focus down to about 2.2metres. With a 12mm extension tube it seems to focus down to about 1.2m.
Has anyone else tried this? I have encountered some problems though and I hope someone else may have some experience.
- When zoomed out, focusing is extremely difficult
- When zoomed in (500mm) performance is better but often auto focus heads off in the wrong direction (the tubes include all the electronic connections to allow for autofocus)
- Even when it does focus OK, it is very slow and I can't see why it should be so
- When focusing at a short distance, the camera seems less fooled. At a a distance of around 20m (it can't focus much further away than that, you can't have everything!), the camera "thinks" the object is around 125m away. You can see this by looking at the image meta-data.
Below are some very boring test images. The first of each pair is with no extension tube. The first pair is around 2.2metres and the second around 20metres. As you can see there is nothing much different in the image quality and very little difference in the angle of view, (the ones with the extension tubes are just slightly zoomed in at 20m and completely normal focused close).
Finally, some real photos, (they wouldn't stay still for me to do a comparison). The Silver Eye is around 3metres the Kestrel around 20 metres, they have been cropped a bit.
All good with me Roger! Fascinating stuff :)
Here's one at about 1.1metres, a cooperative (if scruffy) Crimson Rosella.
Hi Roger, I don't think ext tubes make things darker in the lens like converters do, but your lens at 500mm from memory has an aperture of f6.3 so it wouldn't take much to throw the AF out if it did darken or restrict the light to the AF sensor and if your camera is using Phase Difference AF then the more distant subjects don't quite have the contrast as the near subjects and this could also be making the AF struggle a bit, then again it might be something totally different, it's just an opinion.
Regards
Shane
Phase Difference AF! A whole new subject for me to learn. One problem I have is I have the auto-focus assist illumination turned off, (because it frightens the birds). I wonder if "Phase Difference AF" needs that light? My friend Mr. Google might know, thanks Shane.
The kit of extension tubes come with a 12mm, 20mm, 36mm, and two end caps. You can use all or any of them to vary the length. From results so far I don't imagine the longer ones will work with a long telephoto. I will post another "A Photographic Discussion" post when I have tried the 20mm one.
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For anyone who is interested, I am using a Nikon D300 with a Sigma 150-500 lens.
I also recently purchased a Nikon D5100 body which has higher resolution (megapixels) but has much less convenient controls.
Hi Roger, did you sharpen or crop the photo of the Rosella later? Well, my general comment would be, as frustrating as the limitations of our cameras are, we have to work with that, you can't have it all, or can you? I show you the absolute closest I can do with my lens. The Sony 70-400. The Robin sat right on my shoe, I'm 165 cm tall, the lens was fully extended to 400mm , you can calculate how close that was. The photo is as is, pretty crappy.But tell me, when do you have a bird sit on your shoe?
M-L
I am glad M-L that you didn't get the spelling wrong for your last sentence, because I have had a bird do that to my shoe.
Regards
Shane
For the demonstration I guess I shouldn't have but I did a little bit. The only cropping was to make it the right shape, just a few pixels
off the right hand slide. Are you watching Earthflight? Incredible! Channel 90 right now
Not on my shoe, but I have had a Flame Robin land on my head and a Striated Thornbill on my shoulder and on my camera! I guess focusing close wouldn't really help!
Roger i am no scientist but Phase Difference/Detection AF works by dividing the area into two halves picking out lines of contrast or something to that effect and then comparing the two together because the contrast changes as the focus goes in or out and then works out focus on that when the two out of phase images line up,a bit like the old manual focus split screens on film cameras, except this does it way faster. This is a rough explanation, with the older PD AF systems it used to use horizontal lines in the image to calculate this; now they use cross type sensors which gauge horizontal, vertical and diagonal references to do this which is the fastest not necessarily most accurate way to focus. If your camera has "live view" and you are using that then another system is utilized which in my camera is called Contrast Detection which sounds a bit similar but works on a different principal by looking for contrast between the edges of the focus area, this is the system used in Live View because PD AF won't work while the mirror is locked up which is what happens in Live View mode. My camera also has Imager AF while in Live View and apparently it speeds up the process with designated lenses which I only have one of and don't really use that lens.
The reason I read up a little on this was because I have taken dozens of photos of Red-backed Fairy Wrens and though I have some usable photos I don't have anything that I would call Sharp, photos of other Wrens I can get sharp I put this down to the R-b Wrens being black with some red and often with a darker treeline or background behind it and I think it might make my AF play up because it can't get enough contrast to focus fully. I use spot focus and metering and try for sharp focus on the eye of the bird and I think in this instance because their eyes and surrounds are so black it can't calculate accurately what should be focused on. This is purely my theory on this because I have taken photos of R-b Fairy Wrens which I seriously believed should have turned out better, with an aperture of F5.6, speed of 1/000sec IS on and steadying on a fence post in sunlight, you sort of know sometimes when they should be good. Phew I said that in one breath. I think auto-focus assist illumination is when the light is weak and it will use that to achieve a focus reference.
Regards
Shane
With extension tubes, they’re best used on relatively fast lenses for starters. In the super telephoto range (since your Sigma zooms up to 500mm, it’s considered super tele) a fast aperture would be f/4. Your f/6.3 will introduce focusing problems because of the fact the extension tube increases exposure time by allowing less light to hit the sensor. This would possible make the effective aperture something like f/8 or so, since at f/6.3 the lens’ maximum aperture is just over the useable threshold for most consumer camera bodies.
Not sure 100% whether your camera can actually autofocus well enough with the naked zoom lens zoomed into 500mm when your maximum aperture will be f/6.3. That is an aperture most consumer cameras theoretically should start to not be able to accurately autofocus at. Only a high-end Nikon or Canon (1D series) body can autofocus accurately (albeit slowly) at an aperture between f/5.6 and f/8. For example, my EOS 1DMkIIn body can autofocus (slowly) my 500mm f/4L IS USM lens with stacked teleconverters that make it a lens with an effective focal length of 1,400mm f/11 aperture. While the only reason AF works is because the 2x goes onto the lens first with the 1.4x between that and the camera and effectively the camera body ONLY reads the 2x there, thinking it’s an f/8 lens. I have tried the 400mm f/5.6L lens with a 2x making it 800mm f/11 lens and it did not AF at all. Not sure if this is confusing or not?
I hope my answer is not too over the top with technical detail, but it should be a useful guide.
In my opinion, lose the tubes for birds and get closer, or bring them closer to you.
What camera body do you use? That will also make a HUGE difference.
. I have tried the 400mm f/5.6L lens with a 2x making it 800mm f/11 lens and it did not AF at all. Not sure if this is confusing or not?
By taping over the first three connections between the camera body and the converter will allow the camera to continue using auto focus with the converter, although you may get some hunting.
All very interesting, and yes, confusing. I seem to be getting the best results by focusing manually untill it's close and then trying the auto. I'm not sure the benefit of being able to focus close is worth all the grief but the whole experiment has been fun, thanks for your thoughts everyone.
I also had some fun using a 50mm standard lens with the tubes for some macro shots, (see http://birdsinbackyards.net/forum/King-Parrot-Feather). They need lots of light though. From memory, they were about 10 second exposures!
Regards Roger
Great discussion here guys..... :)
Sunshine Coast Queensland
Thanks for the tip regarding taping pins. I am aware of this taping trick and tried with my 30D when I was trying to achieve AF at f/8 and it was miserable. The non-pro bodies just don't AF well enough at apertures smaller than f/5.6 and even then it's slower sometimes than using a bare lens.
I never considered doing this taping trick using the 1D body, as I know it's reasonable with AF at f/8 and was only trying it once. I can use my 500/1.4x combo and have f/5.6 with awesome AF funcitonality. With stacked converters the camera can only read the 2x, so while I have a 2x and1.4x on, making an effective 1,400mm f/11 lens, the camera thinks it's only f/8 hence why the AF works. Stacked is very slow even using a 1D body.
Roger, you still didn't say what camera body you use! :-)
Roger stated earlier that he puts his Sigma on a Nikon D300 body and has a Nikon D5100 for his other lens.
Regards
Shane
I thought I read somewhere that you can autofocus sometimes when the largest aperture gets above F5.6 by using spot metering and maybe it only works for certain cameras.
Regards
Shane
Sorry, it was all written under a line, which I assumed was just a signature as some people seem to do a line, then signature so I totally didn't notice. Thanks
Most consumer camera bodies will not autofocus slower than f/5.6, although as Headsie said, you can cheat with Canons by taping the three contacts on the lens, it's not very useable. Only pro bodies like a D3, D4 (I think that's all for Nikon) and the 1D series up to MkIV and 1Ds MkIII can AF slower than f/5.6 and even then at f/8 only.
You guys have been talking about long lenses. Do you use tripods with them? I have a 70-300mm on my NikonD90 and would very much like a longer lens but I worry I'd have to start carrying a tripod with me because of its heaviness and that would then restrict my ability to take shots of birds in flight. I have bought some extension tubes - they were advertised as being suitable to use with my camera - but they don't work. Something about the electronics so I'll have to sell them to someone else I guess. Got them from ebay but was hoping it would help to add to my 300mm.
Kathiemt
Selby, Victoria
Kathiemt I always carry a monopdod with my 400 lens - it doubles as a walking stick when the return walk seems a long way....
Steve
Yes, I've thought of doing that. I do have a monopod in the car - I often forget to take it out of the car! Mind you, I broke my leg while out on a nature walk last December, in hunt of Powerful Owls and I have a crutch I walk with at the moment. Perhaps I should swap it for the monopod! The 400mm is sounding more attractive by the minute :-)
Kathiemt
Selby, Victoria
Kathie
I use a carbon fiber tripod with a Wimberley MkII gimbal head when I do use a tripod. I often also shoot hand holding with a 500mm lens and 1.4x converter. Occasionally, even with a 2x, though I do prefer a tripod for that combo. CF tripods are light, the Wimberley MKII gimbal is also perfect for flight photography, especially the medium/large subjects in particular. You don't need to hand hold constantly, there are times you may want to rest your arms and it does take getting used to super telephotos with the weight etc. It's a trade-off though and if I had to use a tripod, I'd definitely do that and improve my shooting possibilities than use a shorter lens and crop the images severely.
a 400mm lens will not give you all that must more magnification really, and if you have no IS or OS or VR (image stabilization) it can become rather difficult to get good shots at lower shutter speeds in low light. Also, if you want a lens for just birds, then buy a prime super tele, not a zoom. I don't like zoom lenses personally, hence why I suggest a prime. With bird and wildlife photography, I have hardly ever needed less than 300-400mm focal length!!! Rarely!!!!
Yeah, probably time for me to look for a prime. I'll have to do my homework and see what I can manage $$wise.
Kathiemt
Selby, Victoria