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Full Version: Macro extension tubes
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I love these but each time I come to use them I'm faced with a dilemma as to which one and which lens. Does anyone have a calculation method that can be adopted to work out focusing distances with different lenses - rather than slapping one on and trying it out each time!!?? Is this indeed possible? I don't have a head for sums I'm afraid - though I do try!!
Indeed, is there even an app for this???? (ever hopeful!!)
Hi there bigcat,
I found I had a similar problem when I bought a set of Kenko tubes a few months ago, much cheaper than a macro lens! I use them with a 50mm prime or 55-300mm telezoom mostly, depending on what I'm doing.

I found the easiest way to make life simple (for me!) was to set the camera on a tripod in the kitchen and a subject (in this case a bowl of flowers) on the kitchen table and then test each lens/tube combination by moving the flowers up and down the length of the table until I had sharp focus. I then measured the distances with a tape measure and noted down the results. These were then transferred to a postcard, laminated and stored in the camera bag.

I'm sure there is a formula for calculating all these settings but, at least with my simple method, after a couple of hours experimenting the answers are there on a card whenever needed. Hope this helps solve your problem.
(Oct 21, 2013, 06:47)KeithB Wrote: [ -> ]Hi there bigcat,
I found I had a similar problem when I bought a set of Kenko tubes a few months ago, much cheaper than a macro lens! I use them with a 50mm prime or 55-300mm telezoom mostly, depending on what I'm doing.

I found the easiest way to make life simple (for me!) was to set the camera on a tripod in the kitchen and a subject (in this case a bowl of flowers) on the kitchen table and then test each lens/tube combination by moving the flowers up and down the length of the table until I had sharp focus. I then measured the distances with a tape measure and noted down the results. These were then transferred to a postcard, laminated and stored in the camera bag.

I'm sure there is a formula for calculating all these settings but, at least with my simple method, after a couple of hours experimenting the answers are there on a card whenever needed. Hope this helps solve your problem.


Good gracious - brilliantly simple. I'd never actually thought of moving the subject! Moving the camera was a guddle. Thank you. Guess what I'll be doing later today!
Glad to be of assistance. Just don't knock the flowers over. Her indoors was not amused!
(Oct 21, 2013, 08:24)KeithB Wrote: [ -> ]Glad to be of assistance. Just don't knock the flowers over. Her indoors was not amused!

Chuckle!!
How are you getting on with the tubes?
(Oct 24, 2013, 08:48)KeithB Wrote: [ -> ]How are you getting on with the tubes?

Yikes! Not done anything yet. Mind you, I do have a vase of flowers now!! Will see if I have time to play Sunday night-if I can stay awake!!
Thanks for asking. Wink
Have this macro sampling shoot done. I do like to see it it goes well? Probably other things or issues or tips we should get in mind you encounter during the shoot?