What are the difference between Auto Extension Tube Set, Helicoid Extension Tube and the Marco Lens for Pentax 645N system

[cl_ho2]

As listed in the Pentax catalogue, there are 3 methods to take macro

photos :

 

1. Auto Extension Tube Set

 

2. Helicoid Extension Tube &

 

3. FA 120mm Marco Lens

 

What are the different results using the above equipments ? What are

the advantages and disadvantage of these equipments ?

 

Thanks for your advice.

[jay_.]

I have a helicoid extension tube for my Hasselblad. It's really a great device. More useful than fixed extension tubes, more compact than a bellows.

[randy_samos]

For starters, most of these methods work in the same way. They are designed to move the lens away from the body enough to do some level of magnification.

 

1: Auto Extension tubes. Just a metal tube with whatever connectivty it needs to couple the aperature and whatever else the body needs to see from/do to the lens. They work just fine, but if you're not metering TTL, then you need to compensate for the extension on your own. Also - if you want to change magnification or focus at infinity, you need to remove the tube.

 

2: Helicoid Extension tube - This is an auto extension tube that adjusts in length. No need to change it out for another if you want to change magnification. Still need to remove it if you want infinity.

 

3: Macro lens - best solution. Mostly, a lens optimized for close focusing that has a built in helicoid extension tube. Though - it will focus at infinity as it is.

 

/r