Alpa Short Barrel lenses
An explanation of Alpa Short Barrel lenses.
By Paul Slotboom Summer 2010
Alpa short barrel (SB) lenses were developed solely to work in conjunction with the 6 degree and 12 degree tilt and swing adapters (T/S). Since the T/S adapters inherently add space to the optical path, if that space was not compensated for in some way, they would behave as extension tubes, as well as tilt and swing mechanisms.
The solution to this problem is to shorten the barrel of Alpa lenses by the exact same distance as the T/S adapters take up. This distance is exactly 34mm. So, SB lenses have 34mm removed from the lens mount to accommodate the T/S adapter and allow the lenses to focus to their full range of distances.
In the event that a photographer does not have or always want to use a T/S adapter, Alpa provides, as an accessory, a 34mm multi purpose spacer to fill this missing space to allow for general purpose photographs with the SB lens.
It is important to understand that it is only lenses of 80mm and longer that have barrels of sufficient length to remove 34mm from. So for this reason only 80mm and longer lenses are produced in a SB design.
Optechs Digital strongly recommends to our customers to consider purchasing all lenses of 80mm and longer in the
SB design, along with a 34mm spacer. By doing so, you will not limit yourself from the future use of the T/S adapters; which are phenomenal accessories for many different photographic intents, both creative and precise.
There are some very nice secondary benefits to SB lenses that we have discovered as well.
- If you have several SB lenses, you only need one 34mm spacer or T/S adapter. This means that your lenses will take less space in a case and will weigh less than the standard barrel equivalent lenses.
- It is very nice to have the 34mm spacer to use as an accessory extension tube on shorter lenses for closeup photographs.
- It is useful to be able to split the size and weight of long lenses between the front side and the backside of your camera for better balance on the tripod.
Please email me if you have questions regarding the information in this article.
