The type of photography that you are planning to use is an important decision factor. Here we have evaluated the SG-image 25mm F1.8 and the Tamron 17-70 F2.8 Di III-A VC 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. Tamron 17-70 F2.8 Di III-A VC is the longer of the two lenses at 119mm. The SG-image 25mm F1.8 with a length of 32mm, is 87mm shorter. Besides being longer, the Tamron 17-70 F2.8 Di III-A VC also has a larger diameter of 75mm compared to the SG-image 25mm F1.8's 67mm 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. SG-image 25mm F1.8 weighs 145g, which means it is 380g (72%) lighter than the Tamron 17-70 F2.8 Di III-A VC which has a weight of 525g.
Filter Threads
The SG-image 25mm F1.8 has a filter size of 52mm whereas the Tamron 17-70 F2.8 Di III-A VC has a 67mm diameter. Larger filters are generally more expensive than the smaller ones given all the other features are equal.
Below are links to the 52mm filters that we recommend you to consider for the SG-image 25mm F1.8:
And these are the 67mm filters that we recommend for the Tamron 17-70 F2.8 Di III-A VC:
Lens Mounts
Both the SG-image 25mm F1.8 and the Tamron 17-70 F2.8 Di III-A VC has the same Fujifilm X lens mount. Some of the latest released cameras that are compatible with the Fujifilm X lenses are Fujifilm X-T30 III, Fujifilm X-E5 and Fujifilm X-M5.
SG-image 25mm F1.8 is also available in the Sony E and Nikon Z mounts.
Tamron 17-70 F2.8 Di III-A VC is also available in Sony E mount.
Focal Range
SG-image 25mm F1.8 is a prime lens with fixed focal lenght of 25mm which has an effective (full-frame 35mm equivalent) focal range of
37.5mm when used on a APS-C / DX format camera.
On the other hand, the Tamron 17-70 F2.8 Di III-A VC has a focal range of 17-70mm and 4.1X zoom ratio which has an effective (full-frame 35mm equivalent) focal range of 25.5-105mm when used on a APS-C / DX format camera.
