Micro Four Thirds Focal Reducer Shootout

Started Feb 20, 2014 | Discussions thread
s_grins Forum Pro • Posts: 12,460
Re: Micro Four Thirds Focal Reducer Shootout

brian wrote:

s_grins wrote:

Brian, out of topic I have a question to you:

There are front mount wide angle lenses that reduce FL. In what way your back mount focal lens reducers are different?

Thanks in advance



Wide angle front attachments do decrease the focal length like a focal reducer does. The main advantage of this type of attachment is that doesn't require that your main lens have extra covering power. In other words, the image circle diameter of the main lens is not changed. Also, this type of attachment is very useful for creating anamorphic lenses, but that's a very specialized application.

Against this advantage are the following disadvantages:

1) Rear focal reducers increase lens speed, while front attachments do not.

2) Good rear focal reducers increase MTF, while front attachments invariably do not.

3) Rear focal reducers are extremely compact, and in fact they reduce the length of the system, while front attachments are very bulky and make the system much bigger.

4) Good rear focal reducers can be used with almost any SLR lens, while front attachments are restricted to a narrow range of lenses.

5) Good rear focal reducers don't impact the focusing performance of the main lens, while front attachments can introduce significant aberrations as focus is changed.

Thank you for great and very detailed answer. I hope I'm not the only person who has read your explanation.

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