Kenko Extension Tube Set DG

orangepeel · 13-07-2006, 13:02

Anyone got these? : -
Kenko Auto Extension Tube Set DG
THK Photo Products, Inc.

What do you think of them? Do they do the job well?

Seems vastly cheaper than buying a macro lens so I'm wondering what the downside is...

***Dave*** · 13-07-2006, 13:32

Stepheno is better placed to advise after his thread here :- Stamens.....

orangepeel · 13-07-2006, 14:11

ta. posted there instead

***Steve*** · 13-07-2006, 14:33

I have and use the Jessops equivalent set. Other than having a different name on the side they are identical (although more expensive) but as I needed them in a hurry I took the hit.

What would you like to know?

***Steve*** · 13-07-2006, 14:37

Edit just followed the link

For macro work (especially with extention tubes) you are better using manual focus as the dof becomes very small indeed. The kenko and Jessops tubes will both maintain AF if you want it to though. With regard to closest focus distance then it depends on which tube and with which lens you are using it but uisng the largest tube (or combination of tubes as they can be stacked) will get you so close that the front of your lens will be touching the subject matter.

orangepeel · 13-07-2006, 14:41

Might as well take real world examples.

I have a 70-300mm which has an MFD of 1.5m, using the smallest tube (12mm) what will that bring the MFD down to? Is there a formula where you can work it out?

***Steve*** · 13-07-2006, 14:44

Thats a bit technical

being serious for a moment, I am sure that there is a formula although I don't know it and unfortunately I don't own a 70-300 lens that I could try it with for you.

neos · 13-07-2006, 23:02

Found this which might help

Fd=Fl + (Fl*Fl/E) or FL plus (FL squared divided by E)
Where: Fd=focus distance, Fl=focal length of lens, and E=extension from the camera body

Fd=300 + (300*300/12)
90000/12=7500+300
7800

7800 what, mm? obviously not

orangepeel · 13-07-2006, 23:43

dunno, looks plausible to me

thanks.

***Steve*** · 17-07-2006, 12:57

Quote:

Originally Posted by neos

Found this which might help

Fd=Fl + (Fl*Fl/E) or FL plus (FL squared divided by E)
Where: Fd=focus distance, Fl=focal length of lens, and E=extension from the camera body

Fd=300 + (300*300/12)
90000/12=7500+300
7800

7800 what, mm? obviously not

orangepeel · 17-07-2006, 16:56

I'll find out soon enough. See if I can work out some sort of formula

***Dave*** · 17-07-2006, 17:05

Quote:

Originally Posted by orangepeel

See if I can work out some sort of formula

Now you sound like a mad scientist ....."He's ALIVE"

**stepheno** · 18-07-2006, 08:09

OP asked about MFD with extension tubes on this thread

I still don't know the actual distances but to give you some idea of effects of the tubes I took some quick shots. They are all hand held so don't be too critical. On the first the FD is about 18 inches and on the last one the lens is touching the flower.

50mm 1.8 only

50mm + 13mm tube

50mm+13mm+21mm tubes

50mm+13mm+21mm+31mm tubes

Hope that helps some.

PS - forget to add that these are the Jessops tubes but they are identical to Kenko.