Sigma 70-300mm f/4-5.6 DG Macro APO

Name: Sigma 70-300mm f/4-5.6 DG Macro APO
Brand: Sigma
Rating: 7.3 (31 reviews)

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Lens Review
Specifications
Description

70-300mm	$199 average price

Lab Test Results

Blur
Chromatic Aberration
Vignetting
Geometric Distortion

Blur
Chromatic Aberration
Vignetting
Geometric Distortion

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SLRgear Review
January 19, 2008
by Andrew Alexander

With the 70-300mm ƒ/4-5.6, Sigma has had an economical competitor to the major manufacturers' consumer telephoto zooms for some years now. There are two versions of this lens, with and without the APO designation; APO signifies that more than one super-low dispersion lens element has been used, and is said to reduce the effects of chromatic aberration. The subject of this lens review is the APO version, and is differentiated from the non-APO lens by a red stripe around the forward part of the lens barrel.

The 70-300mm ƒ/4-5.6 is designed to fill a 35mm frame, but functions properly on a reduced-frame sensor as well. On these types of cameras the lens will provide and equivalent field of view of 105 - 450mm (1.5x sensors) and 112 - 480mm (1.6x sensors). This lens is not yet available in the 4/3rds mount system. To economize and create a more efficient design, the lens is equipped with a variable aperture; as the zoom extends the focal length, both the smallest and the largest apertures change. The following chart represents the largest and smallest apertures you can expect at a given focal length:

Focal length	70mm	100mm	133mm	190mm	300mm
Largest aperture	ƒ/4	ƒ/4	ƒ/4.5	ƒ/5	ƒ/5.6
Smallest aperture	ƒ/22	ƒ/22	ƒ/25	ƒ/29	ƒ/32

The Sigma 70-300mm ƒ/4-5.6 APO DG comes with a circular lens hood and lens pouch, and is available now for around $200.

Update (February 2, 2009): A reader asked us to evaluate the sharpness performance of this lens with the macro switch enabled, as there is a popular opinion that image quality is substantially improved in this case. Our results can be found in the Macro section of this review. In summary: no change.

Sharpness
In general, the 70-300mm ƒ/4-5.6 offers above-average results for sharpness; when stopped down, and kept below 200mm, results are excellent. The sharpest focal length / aperture setting on our sample was 70mm at ƒ/11, where the image was almost tack-sharp across the entire frame.

The lens seems to have been optimized to perform best at its 70mm setting, where the best results for sharpness can be found. When shot wide open at ƒ/4 on the 20D, image sharpness is good (~2 blur units, just slightly better in the center), improving substantially when stopped down to ƒ/8 and ƒ/11. It's almost the same story at 100mm, but by 133mm the lens never hits the same level of "tack-sharp" that can be seen at shorter focal lengths. At around 200mm our copy of this lens showed significant corner softness and some de-centered flaws (the bottom of the frame is softer than the top); 300mm has a small sweet spot of above-average performance near the center of the image and substantial corner softness (~3 blur units in the center, upwards of 4-7 blur units in the corners).

On the 5D, performance is similar, but the lens is pushed to the limit as the corners are much more soft on the full-frame sensor. Again, 70mm offers the best performance when comparing apertures and focal lengths, as corner softness appears at 100mm and gets substantially more prominent as the lens is zoomed closer to 300mm. Stopping down to ƒ/8 or ƒ/11 helps a bit, but by 133mm corner softness is always a factor. At 300mm, corner softness is off the charts until ƒ/22, and central sharpness isn't that great, either.

Image sharpness with the lens stopped down fully (ƒ/22 - ƒ/32) is surprisingly good until around 133mm (~3 blur units). At focal lengths longer than that images are uniformly soft, but in the case of 300mm, image quality is a bit more evenly soft than at wider apertures, where the corners are off the charts for softness in comparison to the center.

In short, this may not be the lens you want to turn to if you're looking for consistent corner-to-corner sharpness, but if you're looking for subject isolation - sharp center, soft corners - the lens does this quite well.

Chromatic Aberration
Sigma promises good resistance to chromatic aberration thanks to its APO glass, and our test results bear this out. At 70mm CA is almost non-existent across all apertures, on both sub- and full-frame camera sensors. At the focal length is increased CA does increase as well, but it never surpasses 6/100ths of a percent of frame height in the corners, in either full- or sub-frame sensors, making it fairly hard to detect by the naked eye. Overall, excellent performance here.

Shading (''Vignetting'')
On the sub-frame 20D, the 70-300mm ƒ/4-5.6 produces very little in the way of corner shading; when shot wide open, the corners are just over a quarter-stop darker than the center, but that's the extent of it. Anything else and there's no difference.

The story's completely different on the full-frame 5D, where there's substantial corner darkening when the lens is used in the majority of its focal length / aperture combinations. On average, the corners are one full stop darker than the center. Curiously, the best results are obtained at either 70mm or 300mm, where the worst effects of corner shading only occur with the lens open to its widest aperture. Stopping down 2-3 aperture settings reduces the vignetting effects to 1/3 of a stop or less.

Distortion
The 70-300mm ƒ/4-5.6 is optimized at 70mm to counter distortion: at that setting, there is almost 0% distortion, making that the preferred setting. As the focal length is extended through the zoom range on the sub-frame 20D the corners exhibit pincushion distortion - at its worst point, 133m, our tests show -0.4% distortion - and there is a general barrel distortion throughout the image of around +0.1%.

On the full-frame 5D distortion is a bit more significant, but follows the same pattern. By 133mm corner distortion is a fully -1.0% pincushion-distorted and the center is +0.5% barrel-distorted. These aren't big numbers, but if you need your straight lines to be straight, you should be aware of them.

Autofocus Operation
The 70-300mm ƒ/4-5.6 APO isn't an HSM lens, but it does use a built-in electric motor to focus. The result is a fairly fast focusing lens that produces some noise while focusing. The focusing ring will turn while the lens autofocuses, as will the front filter element. As well, the lens will extend slightly throughout the range of focus. Note that for Nikon there are two versions of this lens, in that the newer one of the two will focus properly on D40, D40x and D60 bodies.

Macro
The 70-300mm ƒ/4-5.6 is designated as a macro lens, providing up to 1:2 (0.5x) macro magnification when set to the 300mm focal length. Macro use is restricted to 200-300mm. At 200mm this magnification is 1:2.9. Minimum close-focusing distance is just over three feet (37.4 inches, 95 cm).

Update (February 2, 2009): A reader asked us to evaluate the sharpness performance of this lens with the macro switch enabled, as there is a popular opinion that image quality is substantially improved in this case. Intrigued, we put the lens into the same test setup and did the retest, with the following results:

Results (central BxU), 300mm

Aperture	Original test (macro OFF)	Retest (macro OFF)	Retest (macro ON)
f/5.6	2.860	2.630	2.695
f/8	2.455	2.345	2.365
f/11	1.993	1.878	1.883
f/16	2.043	2.065	2.095
f/22	2.803	2.888	2.888
f/32	4.395	4.515	4.543

In short, the results are essentially the same whether the macro switch is engaged or not; it appears to act as a focus limiter rather than engaging some form of alternate configuration of lens elements.

Build Quality and Handling
The Sigma 70-300mm ƒ/4-5.6 is composed mainly of plastic, however the overall impression is that the lens is quite rugged. The lens mount is metal and the filter rings are plastic. The lens barrel is black, which a semi-roughed finish. The focus ring is mounted near the front of the lens, the zoom ring towards the lens mount, and both are composed of a nice rubber ridged pattern that is well-dampened and easy to grip.

The lens provides the user with a distance scale marked in imperial and metric units, as well as a depth-of-field scale for ƒ/11 and ƒ/22. There are switches for autofocus operation (on or off) and macro mode activation; above 200mm you can engage the macro mode.

The generous zoom ring (1 1/8 inches wide) is well-dampened, requiring slightly more torque to move, no doubt designed this way to prevent zoom creep. The lens does not have a switch to lock the zoom to 70mm. It takes about ninety degrees to run the lens through its entire range of focal lengths, and doing so extends the lens by 2 1/8 inches as it approaches 300mm.

The focus ring is mounted at the far end of the lens. It uses a different texture than the zoom ring, more like that of the body, and is about a half-inch wide. It offers about ninety degrees of movement for manual focusing and is linked to the focus motor so you'll need to disengage the autofocus to adjust the focus manually. The front element does turn during focus operations, making life that much more interesting for filter users. There are hard stops at the close-focus and infinity ends of the focus spectrum, and the lens will focus past the infinity mark.

The LH635-01 lens hood, a circular and bayonet-mount affair, comes with the lens as a package however wasn't part of the sample we received from Sigma. Looking on the net it appears not to be flocked or ribbed, but has a smooth and matte finish on the interior. We've confirmed it will reverse for storage on the lens.

Alternatives

Nikon 70-300mm ƒ/4.5-5.6G IF-ED AF-S VR ~$529
The Nikon's results for image sharpness are dramatically better than that of the Sigma, especially when shot wide open. Chromatic aberration is controlled better by the Sigma, and they're about the same for distortion and corner shading. Note we haven't tested the Nikon on a full-frame body. The Nikon offers vibration reduction and AF-S focusing.

Canon EF 70-300mm ƒ/4-5.6 IS USM ~$549
The Canon performs very well, providing excellent results that best the Sigma in almost every category (the Sigma is still excellent at resisting chromatic aberration at 70mm).

Pentax 75-300mm ƒ/4.5-5.8 AL SMC P-FA J ~$130
While there is a newer version of this class of lens (the Pentax 55-300mm) we haven't yet tested it; the 75-300mm provides about the same performance as the Sigma, with the Sigma providing better results for tolerance to CA. The Pentax offers less distortion.

Sony 75-300mm ƒ/4.5-5.6 ~$200
The Sony performs about as well as the Sigma, but the Sigma bests it for tolerance to CA. Distortion is better controlled by the Sony.

Conclusion
The Sigma 70-300mm ƒ/4-5.6 is a viable alternative to manufacturers' versions of the same lens. If you're looking for excellent corner-to-corner sharpness across a wide range of focal lengths and apertures you won't find it in the Sigma, but when stopped down to ƒ/8 and ƒ/11 the lens performs decently well. It offers an excellent macro mode between 200mm and 300mm and some of the best resistance to chromatic aberration that we've seen in lenses of this category, all for a very reasonable price.

Sample Photos

The VFA target should give you a good idea of sharpness in the center and corners, as well as some idea of the extent of barrel or pincushion distortion and chromatic aberration, while the Still Life subject may help in judging contrast and color. We shoot both images using the default JPEG settings and manual white balance of our test bodies, so the images should be quite consistent from lens to lens.

Still Life shot

VFA target

As appropriate, we shoot these with both full-frame and sub-frame bodies, at a range of focal lengths, and at both maximum aperture and ƒ/8. For the ''VFA'' target (the viewfinder accuracy target from Imaging Resource), we also provide sample crops from the center and upper-left corner of each shot, so you can quickly get a sense of relative sharpness, without having to download and inspect the full-res images. To avoid space limitations with the layout of our review pages, indexes to the test shots launch in separate windows.