Sky & Telescope - January 2022 - 31

Cropped vs. Full Frame
Once you narrow your choice of lens, the next step is to
check if it will work with your camera. It has to fit your
brand of camera, but it also has to fit your type of camera
within that brand.
For example, Canon has four different types of lenses: EF
(for all its DSLRs), EF-S (for just its cropped-sensor DSLRs),
EF-M (for its M series of mirrorless, cropped-sensor cameras),
and RF (for its R-series of mirrorless, full-frame cameras).
Got that?
Nikon has its decades-old F-mount from the film SLR
days and carried over to its DSLRs, as well as the new
Z-mount lenses for its mirrorless cameras. Sony offers
E-mount lenses, Leica and Panasonic require L-mount
lenses, Fujifilm uses its X-mount and medium-format
G-mount, while the Pentax standard is called the K-mount.
Yes, we have standards. Lots of them!
The other spec to check is if the lens will work with your
camera sensor. That appealing fast lens might be only for
cropped-frame cameras. Sometimes you have to dig into the
specs to see if that's the case. It might say it's for DX or APSC,
terms camera manufacturers use for their cropped-frame
sensors. Even if it can physically connect to your brand of
lens mount, such a lens won't project an image circle large
enough to fill a full-frame sensor. The vignetting will be
extreme, and no amount of post-processing will fix it!
If yours is a cropped-frame camera, then a croppedframe
lens will be just fine. Nevertheless, be mindful of two
considerations. First, the smaller sensors of cropped-frame
cameras provide a narrower field of view with any given lens
or focal length. It takes a 12-mm lens to provide the same
actual field of view as a 20-mm lens does on a full-frame
camera. For example, Samyang (aka Rokinon in North
America) has a fast 12-mm f/2 in several versions, but it's
only for cropped-sensor cameras.
Second, keep in mind that if you invest in a lot of lenses
Lens Field of View (FOV)*
Focal Length
Full-Frame
(35-mm)
Camera
8-mm Circular Fisheye
11-mm to 12-mm
Rectilinear Fisheye
14-mm
20-mm
24-mm
35-mm
50-mm
85-mm
*Approximate dimensions
that work only on your cropped-frame camera, they'll be
obsolete if you later upgrade to a full-frame camera. Industry
pundits expect Canon and Nikon will introduce few, if any,
new DSLRs in coming years. As with Sony, which discontinued
its DSLRs in 2021, all new cameras will be mirrorless, with
most of those being full-frame. Only Pentax bravely remains as
the manufacturer of just DSLRs, both cropped and full-frame.
DSLR vs. DSLM
DSLRs have vast catalogs of lenses available for them. The
lens selection for the new generation of DSLMs is limited but
growing, both from the original manufacturers and from
third parties. Established lens manufacturers such as Sigma,
Tamron, and Tokina now must compete with names such as
Samyang/Rokinon and Laowa, and most recently by previously
unknown brands such as Irix, Meike, 7artisans, TTArtisan,
Viltrox, and Yongnuo, to name a few.
Many of these startups specialize in lenses just for mirror180°
117°
× 95°
104° × 81°
84° × 62°
74° × 53°
54° × 38°
40° × 27°
24° × 16°
Lens for Similar FOV
with Cropped-Frame
Camera
4-mm to 6.5-mm
7.5-mm to 9-mm
8-mm to 10-mm
12-mm
14-mm
20-mm to 21-mm
30-mm to 35-mm
50-mm to 55-mm
35-mm lens
85-mm lens
sk yand tele scope .o r g * JANUARY 2022 31
https://skyandtelescope.org/
Sky & Telescope - January 2022

Table of Contents for the Digital Edition of Sky & Telescope - January 2022
