Extension tube on a 500mm f4

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JSD

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The minimum focus distance on my Nikon 500mm f4 G is about 12 1/2 feet. I am wondering how well an extension tube would work to get closer. What pros and cons, effect on DOF, image quality or anything else. If anyone has experience with this set up I would greatly appreciate any comments. I see 12mm tubes are available. Thank you.
 
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I've used tubes on my 600mm, 70-200 and a few others. You will lose some light, maybe a stop or two. The longer the FL of the lens, the longer the tube has to be to see a difference. You will lose infinity focus with most all tube lengths. DOF remains about the same though it seems like it's less which is due to the fact your subject is now closer to the camera. I usually use a 20mm tube with my 600, the Vello set of 3 seems to be the best I've found. The Kenko set is ok, but it seems like the electrical contacts fail often, I've had 3 sets before switching to the Vello. Since they don't have lens elements, there isn't any image loss. With less light getting thru the af will take a hit but they will get you a little closer.
 
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JSD said:
The minimum focus distance on my Nikon 500mm f4 G is about 12 1/2 feet. I am wondering how well an extension tube would work to get closer. What pros and cons, effect on DOF, image quality or anything else. If anyone has experience with this set up I would greatly appreciate any comments. I see 12mm tubes are available. Thank you.
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I've used extension tubes on my big Nikon primes many times to improve the close focus distance and magnification. Basically an AF compatible extension tube (I use the Kenko tubes) works fine from an AF standpoint though my longest tube has a bit of excess play that I don't love.

The big downside is you lose infinity or even far away focus so if you're shooting say a small bird up close and a big hawk lands across the field you won't be able to quickly change focus to the distant bird without removing the tube. You also lose a small amount of light transmission but it's pretty small when the tube is on a long telephoto lens as the added extension is a small fraction of the total focal length of the lens.

In terms of DOF, it's the same as if the lens had a closer MFD and you achieved the same image size on your sensor. IOW, there's no added DOF penalty but by achieving a closer focus and a corresponding larger magnification the DOF does decrease for the same aperture.

There's very little downside to adding an extension tube to a big prime lens beyond the loss of long distance focus. I would generally avoid adding extension tubes to zoom lenses as the impact on focusing distances varies with the zoom so you can go a bit crazy chasing focus as you zoom in and out. I tried that for a while with butterfly shots and in the end went to alternative approaches though it's not terrible if you just pick a zoom length and stick with it while the tube is mounted.
 
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JSD said:
Thank you both for the quick replies, much appreciated. Warren suggests a 20mm tube, what size have you used DR?
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The set I have (and these are commonly sold in sets of three all stacked up) has a 12mm, 20mm and 36mm tube. Which tube I use depends on the situation and I've even stacked all three a few times (again there's no optical quality loss as there's no glass in the tubes, just additional lost light, less far focus range and more wiggle due to all the couplings). But I suspect I've used the 20mm and 36mm tubes most often. Unless I'm in a blind or otherwise stuck in a fixed position it's usually as easy to move the tripod back a foot as it is to connect the 12mm tube so it seems I reach for the longer tubes more often as they make a bigger change in close focus distance.
 
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DRwyoming said:
The set I have (and these are commonly sold in sets of three all stacked up) has a 12mm, 20mm and 36mm tube. Which tube I use depends on the situation and I've even stacked all three a few times (again there's no optical quality loss as there's no glass in the tubes, just additional lost light and less far focus range and more wiggle due to all the couplings). But I suspect I've used the 20mm and 36mm tubes most often. Unless I'm in a blind or otherwise stuck in a fixed position it's usually as easy to move the tripod back a foot as it is to connect the 12mm tube so it seems I reach for the longer tubes more often as they make a bigger change in close focus distance.
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Thanks a million DR.
 
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JSD said:
Thanks a million DR.
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FWIW, here's a long lens macro shot I captured with my 600mm f/4, stacked 36mm and 12mm extension tubes and TC-14 II teleconverter. This is the uncropped image out of a DX sensor camera. Basically I was shooting birds from a blind near a watering hole and the bird activity had gone quiet but a few Dragonflies were hanging around. So I slapped together the parts and captured some images like this:

dINDF0131_websize.jpg
You can only see EXIF info for this image if you are logged in.
 
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Even if more expensive try to get a set with metal bodies. I tried it with some of the popular plastic rings with metal mounts and it didn't work well (too floppy)
 
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