Divide focal length of lens into amount of extension = magnification. Belows are basically infinately adjustable extension tubes with greater extension so greater magnification is possible. More fiddly though. For tubes I would highly recommend a focussing rail to make adjustment much easier, bellows have them built in.

Andy: Many people get very good results by putting a close up lens on the front of a prime or zoom lens. The prime should give the best results, but zooms work too. If you choose this route, then make sure you buy a high quality 2 element close up lens, to reduce CA. Canon and Nikon make close up lenses. I have used a Nikon 3T on an old Nikon 75-150 F3.5 zoom with good results. However not all zooms work well with a close up lens. And I'm not sure if the 75-150 would work on your D70 as it is a manual lens.

Yes, I have got the a Canon close up lens and it works very well. They come in different strengths or dioptres and have the advantage of no loss of light.

Sigma 180mm macro lens
 

I use this len and also a Canon 100mm, However for extreme close-ups I always use the Sigma. As this gives a greater working distance, very useful when using extension tubes.

The attached photo taken yesterday is of a spider aprox 8mm in length, for this shot I used the Sigma and a full set of Jessops extension tubes (full set = 65 mm) Flash was also used.

Just minimal cropping so as to frame the subject better.

Harry

That is a super image Harry. Stronger image than the one in your gallery.

Don

Yes, it's a good one. I know from experience how hard it is to take such a picture.

That is a fantastic shot wolfie -really sharp!

I was thinking of buying the Sigma 180 but having read a few reviews and forum discussions I am now leaning more towards the Sima 150. It will still offer a reasonable amount distance from the subject and I have read that it is somewhat sharper than the 180 and offers a greater potential dof.

Having said that, Wolfie's shot shows that the 180 is far from soft. Does anyone have any experience of the two lenses?

My intended subject matter will range from flighty insects, to slow moving whopping great insects to plants and fungi. I'll be using it in the rainforest, so the lighter weight of the 150 is a bonus!

Whatever you get read up about looking after you equipment in the humidity of the rainforest or youy macro subjects like fungi will be living inside your lens!

Something in the range 150-180mm is ideal for flighty insects. But it can be a bit cumbersome for fungi although it will work.

Regarding DOF, you will get the same DOF from a 105mm lens as with a 180mm lens, as long as the aperture and image magnification are the same.

The difference is that a longer lens has a narrower field of view, making it easier to isolate a subject against a smooth background.

And of course a longer lens is usually bigger and heavier.

There are some more reviews on www.PhotoZone.de including the two Sigmas you are looking at.

Leif

Thanks for the info. Mike, storing my gear is certainly on my mind. I'm going to start a new post regarding this.