The type of photography that you are planning to use is an important decision factor. Here we have evaluated the OM System 90mm F3.5 Macro and the Pentax D-FA 100mm F2.8 Macro for their suitability to various photography scenarios:
Size and Weight Comparison
The size of a lens is a crucial factor to consider when comparing two lenses. OM System 90mm F3.5 Macro is the longer of the two lenses at 136mm. The Pentax D-FA 100mm F2.8 Macro with a length of 81mm, is 55mm shorter. Besides being longer, the OM System 90mm F3.5 Macro also has a larger diameter of 70mm compared to the Pentax D-FA 100mm F2.8 Macro's 68mm diameter.
The weight of a lens is equally significant as its external dimensions, particularly if you intend to handhold your camera and lens combination for extended periods. Pentax D-FA 100mm F2.8 Macro weighs 345g, 23% (108g) lighter than the OM System 90mm F3.5 Macro's weight of 453g.
Filter Threads
The OM System 90mm F3.5 Macro has a filter size of 62mm whereas the Pentax D-FA 100mm F2.8 Macro has a 49mm diameter. Larger filters are generally more expensive than the smaller ones given all the other features are equal.
Below are links to the 62mm filters that we recommend you to consider for the OM System 90mm F3.5 Macro:
And these are the 49mm filters that we recommend for the Pentax D-FA 100mm F2.8 Macro:
Lens Mounts
The OM System 90mm F3.5 Macro has the Micro Four Thirds lens mount whereas the Pentax D-FA 100mm F2.8 Macro has the Pentax KAF lens mount. Some of the latest released cameras that are compatible with these mounts are OM System OM-3 Astro, OM System OM-5 II and OM System OM-3 for the Micro Four Thirds Mount and Pentax K-3 III Mono, Pentax KF and Pentax K-3 III for the Pentax KAF Mount.
Focal Range
OM System 90mm F3.5 Macro is a prime lens with fixed focal lenght of 90mm which has an effective (full-frame 35mm equivalent) focal range of
180mm when used on a FourThirds format camera.
On the other hand, the Pentax D-FA 100mm F2.8 Macro is a prime lens with fixed focal lenght of 100mm. When it is mounted on an APS-C sensor camera with 1.5x crop, it provides a 35mm (FF) equivalent of 150mm.
