Is it possible to use an extension tube of let's say 25mm on a 75-300mm zoom to obtain a closer focusing distance and the subject larger in frame? What will be the magnification factor when using this kind of extension tube on this kind of lens ? Thanks for any advice on this.
Yes, and it works. I use extension tubes all the time on my 70-200 for close-up work. Auto focus does not work though. I do not know what the magnification factor is.
I use 25mm extension on my 50-500 whenever I want to do closeup work.
With tubes, the ratio of extension to focal length is important, so the effect of the tube changes as you zoom. At 75mm your range from minimum to maximum focus will be quite small, and quite close to the front of the lens, while at 300 it will not be hugely different than it was without the tube (close focus will be somewhat closer, and you'll lose the ability to focus at larger distances).
When shooting with a tube on my 50-500, I use the zoom control for my main focus control, especially when working with higher magnifications. (Maximum magnification will likely be somewhere in the middle of the zoom range.) AF still works, but the reduction in focus range caused by the tube means you need to get the focus close first by either zooming or moving the camera closer to or further from the subject.
The issue with zooms is that the magnification changes as you zoom, which can take a bit of getting used to. One way to handle is set the zoom and focus by changing distance, if you want to get closer zoom out. Another option is the Canon close up diopters, the 2 element ones are quite good, you don't lose light with them. The basic formula is magnification = extension/focal length .
Yep, does work. As a rule of thumb, you can assume that (at infinity focus) length of extension divided by focal length gives you the reproduction ratio (so if f = 50 mm and you add 50 mm of tubes, you're at 1:1 at infinity, if you only add 25 mm of tubes, you're at 1:2). This of course then can change depending on how the lens is focused, but the closer you get to 1:1, the less effect will focusing have. But if you add something like 30 mm extension onto a 300 mm lens that normally focuses down to 1:2 (Sigma 70-300 comes to mind), using minimal focus distance will give you an extra magnification kick over the "expected" 1:10 at infinity (I'd guess it goes down to something like 1:1.5 or so, even though I've never tried that).
Thanks a lot guys for the information and so I ordered a set of Kenko tubes for under 200$. Not that expensive and they can be used on all other Nikon lenses I own so thanks again for the info.
BTW, in case you own the 50/1.8, this little thing works very nicely for really close close ups using extension tubes (as long as you can get close enough to the subject).
For me the biggest reason to use tubes on a zoom, in spite of its handicaps, is the option to change framing without moving the tripod or using rails. That's a big plus when you care a lot about composition.
Basil, yes I have a 50/1.8 and I will certainly try it out with the tubes.
Hi Danny, nice to here you. Your work has been an inspiration to me so I'm trying to become a better macro photographer. I knew tubes are a great tool for getting closer focus but I wasn't sure using them with a zoom was workable.
Oh yeah Jos, they sure are M8t. Now if you want to, you can actually add in reverse a 50 or 100mm lens in front of a.....say.... 70 -210mm and the ratios are large Jos, make that HUGE M8t. I use to do that with 35mm and I've seen it done a Canon 20D with remarkable results. It takes some getting use to with outside shots, but thats just practise.
Oops, favourite subject , but yes tubes will serve you well my macro friend
Discussion
10 repliesWith tubes, the ratio of extension to focal length is important, so the effect of the tube changes as you zoom. At 75mm your range from minimum to maximum focus will be quite small, and quite close to the front of the lens, while at 300 it will not be hugely different than it was without the tube (close focus will be somewhat closer, and you'll lose the ability to focus at larger distances).
When shooting with a tube on my 50-500, I use the zoom control for my main focus control, especially when working with higher magnifications. (Maximum magnification will likely be somewhere in the middle of the zoom range.) AF still works, but the reduction in focus range caused by the tube means you need to get the focus close first by either zooming or moving the camera closer to or further from the subject.
-Paul
Yep, does work. As a rule of thumb, you can assume that (at infinity focus) length of extension divided by focal length gives you the reproduction ratio (so if f = 50 mm and you add 50 mm of tubes, you're at 1:1 at infinity, if you only add 25 mm of tubes, you're at 1:2). This of course then can change depending on how the lens is focused, but the closer you get to 1:1, the less effect will focusing have. But if you add something like 30 mm extension onto a 300 mm lens that normally focuses down to 1:2 (Sigma 70-300 comes to mind), using minimal focus distance will give you an extra magnification kick over the "expected" 1:10 at infinity (I'd guess it goes down to something like 1:1.5 or so, even though I've never tried that).
Hope that helps and is correct.
Basil
BTW, in case you own the 50/1.8, this little thing works very nicely for really close close ups using extension tubes (as long as you can get close enough to the subject).
Basil
All the best Jos
Danny.
Basil, yes I have a 50/1.8 and I will certainly try it out with the tubes.
Hi Danny, nice to here you. Your work has been an inspiration to me so I'm trying to become a better macro photographer. I knew tubes are a great tool for getting closer focus but I wasn't sure using them with a zoom was workable.
Oops, favourite subject
Danny.