The Sigma APO 150-50mm lens is a moderately fast, super-telephoto zoom designed
to work with both APS-C and full-frame DSLR cameras. It offers quite useful
close focusing (7.2 ft) and two modes of what they deem "optical stabilization"
(OS.) Weighing in at 67.4 oz you always know its there, but then again this
is one impressive piece of glass. I recently worked with the lens in northern
New Mexico.
Having OS is what makes this lens tempting, as you can indeed shoot handheld,
something that I would have previously hesitated to do with a lens of this bulk
and focal length range. The OS system, according to Sigma, works in two modes.
Here's a quick Sigma-supplied overview of how this works:
"Sigma's OS system consists of two types of sensors inside the
lens to detect the angle and speed of vertical and horizontal camera movement.
When shake is detected, a signal is sent to a special motor with instructions
to shift a group of lens elements in the appropriate direction to counteract
the effect of lens shake. This causes incoming light rays to be refracted so
the image is returned to the center of the frame; consequently, the projected
image is stable, allowing for sharper pictures."
Mode 1 is for general picture taking; Mode 2 is for vertical camera shake and
is best for panning or following moving subjects. This assumes, of course, that
your AF system is up to following the subject for you, which, thanks to this
being an HSM lens, works quite well. It is not recommended that you use OS if
the camera is mounted on a tripod. You mount it with the supplied and quite
rugged tripod mount collar, which allows you to move the rig from horizontal
to vertical position simply by loosening then moving then tightening the screw
on the barrel collar. (I strongly recommend not using the camera tripod mount.)
And do not work with a shy or flimsy support--I worked with a Gitzo G2227
carbon fiber and Gitzo G1276M ball head, and would hesitate to mount the camera
and lens on anything less rugged.
|
 |
Near & Far: While a 3X+ zoom ratio does not seem a great leap
it seems to become exaggerated when you work in the super-tele range.
This scene was shot at both the 150 and 500mm setting; note the
painter in the lower right in the 150mm frame.
All Photos © 2008, George Schaub, All Rights Reserved |
|
I received a Canon mount test lens and worked with a 5D and 30D for checking
the results with both full-frame and APS-C sensor, as this lens is of DG Sigma
designation, meaning it can be used on both formats. The effective focal length
range on the 30D, given the 1.6x magnification factor, is 240-800mm, safari-length,
no doubt. The lens focusing and exposure worked spot-on with both bodies.
|
 |
 |
Cloudscapes: Long lenses bring you close to the action regardless
of subject or scene. Being out West during Monsoon season my attention
turned to the sky. |
|
There was a glitch, however. There was noticeable vignetting on the 5D (full
frame) at all focal lengths at any aperture below f/11, becoming much less apparent
at f/16 and above and quite apparent at maximum aperture. I found no apparent
vignetting on the 30D at all focal lengths and apertures. I first saw this on
the edges of some cloud pictures I made, and thought it might be the large lens
hood (included in the lens price) or the nature of the shots themselves, but
later made tests with and without the hood on a flat lit wall and got the same
results.
|
 |
Vignetting: In the first day of shooting I noticed some vignetting
on the 5D images, especially at wider apertures. To check it out
I photographed a blank stucco wall, with and without the lens hood,
with the 5D and 30D with the 150-500mm lens. This verified what
I thought I saw in the general scenes; the lens on the full-frame
5D showed vignetting starting at f/11 and getting more noticeable
as it got wider. The 30D (APS-C sensor) showed no such problem.
I could solve the vignette in ACR, which at about +30% eliminated
it. |
|
The range of the zoom is quite impressive, which belies what I first thought
was a modest 3X+ ratio; somehow when you go 3X on a zoom that starts at150mm
you get into some really long views. Start out at 240mm and it gets really interesting.
|
Handheld
Super Tele: The 500mm setting is difficult to hold steady even at
quite fast shutter speeds, but the OS system in the Sigma comes
to the rescue. I feel very comfortable working with this lens at
1/125 sec with Mode 1 on, but some may be able to shoot at even
slower speeds handheld. |
|
Article Contents
