bnsf

I forgot to mention l will be using a 24 -70 a mount lens on a Sony a99m2 camera.

imagemeister Loc: mid east Florida

The 70mm will not give you much close up working space - especially on FF.

tkphelps

I have a set of Prost auto extension tubes and several Nikon lenses. The 12 mm tube works well with all of the lenses including auto focus and auto exposure features. Using a 12 mm tube and the 35 mm f1.8 lens will get 1.5 inches on a DX sensor or about 1.5:1 reduction (image 1). It makes reasonably flat field and no distortion that I can see. What you pay is a 2 inch working distance which means that lighting can be challenging. I have found that the 20 mm and the 36 mm extension tubes or combinations of more than one tube do not auto focus well because the adjustment range is very short. All the real focusing with these longer tubes is done by moving the camera.
Using a "micro" 105 mm lens with no extension as recommended by one contributor puts 2.25 inches on the sensor at the closest distance, but the working distance is about a foot which makes it much easier to manage lighting. Now if you add a 36 mm extension tube to that lens you can put 11/16 inch on the sensor (image 2). Note that even with a copy stand, the focus is very difficult, but the image is nearly twice life size on the sensor. Also, even though there are contacts on the long extension tube, communication between the lens and camera doesn't work.
The third image is the 18-300 mm zoom at maximum length and set for closest focus with a 36 mm extension tube. This combination has a working distance of about 1/2 inch so lighting is really inconvenient. Note that the image is only 1.25 inches, so that combination is roughly the same as a 50 mm lens and a 12 and 20 mm tube added together. The information here is that for close focus, the zoom is really a wide angle lens.
My experience with macro "filters" is many years old, but at the time, I found that only the center was sharp, even copying flat subjects. I have avoided them ever since. I put my money on the extension tubes.

Fotoartist Loc: Detroit, Michigan

Sounds like a poor lens choice for macro work. You need to reread the comments given and research the topic of macrophotography more, IMO.

oldtigger Loc: Roanoke Virginia-USA

Which one of your tubes has the chip?
Are you placing it on the camera first?

tkphelps

It doesn't appear to matter what the assembly sequence is. The 12 mm tube will autofocus and appears to correctly modify the exposure though auto ISO is on. The 20 and 36 mm tubes will not auto-focus, but it probably doesn't make sense to try to autofocus when you should be varying the distance to the subject. Those tubes also do not couple the lens data, although they do stop down when the exposure is made.
I don't believe the tubes have any processor included though I don't know how to find that out.

Nikonian72 Loc: Chico CA

Using extension tubes with a zoom (all utility) lens is like putting knobby tires on a station (all utility) wagon to go off-roading. It can be done, but you will not be happy with the results.
If you have a serious interest in macro-photography, you should subscribe to the UHH section True Macro-Photography Forum at http://www.uglyhedgehog.com/s-102-1.html
Some of the advice offered on this thread is incorrect. Only factual advice is allowed on the Macro Forum, by actual contributing macro-photographers.

bnsf

Excess me for providing the wrong lens information. I will use the extension tubes in my 50mm f/1.8 lens. I was hoping using the 24 - 70mm lens would give closer photos than a 50mm lens.

bnsf

Excess me for providing the wrong lens information. I will use the extension tubes in my 50mm f/1.8 lens. I was hoping using the 24 - 70mm lens would give closer photos than a 50mm lens.

aellman Loc: Boston MA

"No offense meant," is a convenient disclaimer, but comparing UHH members' opinions to Aunt Sally's knee ache is somewhat offensive and inaccurate. If I were to make use of a similar disclaimer, I might "opine" something like,
"F**k you and the horse you rode in on, no offense meant."

Fotoartist Loc: Detroit, Michigan

What about the OP? **** that too?

oldtigger Loc: Roanoke Virginia-USA

I would not expect to find any processor in the tubes and they should work in any combination or order.
You are right that auto focus is not a necessity for macro work, but it should still function.
The only time i've seen it fail is when there isn't enough light,
which is most of the time when you have 2 or more tubes mounted.
Mount all 3 tubes, point your camera at a real bright subject and try again.

You said: "Those tubes also do not couple the lens data":
What data do you feel you are not getting?

bnsf

Have not purchased them yet.

bdk Loc: Sanibel Fl.

I spent the bucks and bought a good set of extension tubes. They have the electronics so the camera can auto focus.
well I find manual focus is better, tested on all my lenses and all manual focus was better. I should have bought the $25,00 import and set the extra money aside to buy a lens.

RWR Loc: La Mesa, CA

With a prime lens, for a given reproduction ratio I am stuck with one particular subject distance. With a zoom lens, I can achieve a given reproduction ratio at a range of subject distances. For me, this utility more than makes up for the inconvenience of operating a zoom lens with extension tubes in the field. Neither one is best for everybody.