Sigma 50mm Macro lens with 1:1 magnification

Introduction

If one looks for a specialized lens for a specific type of photography, such as macro, a camera’s own manufacturer is the appropriate place to go. Nikon is best known for offering a whole range of lenses for macro photography. With Nikon 35mm system, one has a choice of

1. 55mm f/2.8 AIS Micro-Nikkor Manual Focus (MF) lens,
2. 60mm f/2.8D AF Micro-Nikkor,
3. 85mm f/2.8D Micro-Nikkor PC (Perspective Control) MF,
4. 105mm f/2.8D AF Micro-Nikkor and 105mm f/2.8 AIS MF
5. 200mm f/4D ED-IF AF Micro-Nikkor and 200mm f/4 AIS MF
6. 70-180mm f/4.5-5.6D ED Micro-Zoom AF Nikkor

It is good to know that all the manual focus Micro-Nikkor lenses listed above are still available new from Nikon.

Canon is probably the next camera manufacturer that offers a good selection of lenses for its macro photography system:

1. 50mm f/2.5 EF Macro,
2. MP-E 60mm f/2.8 Macro (1x-5x image magnification),
3. 100mm f/2.8 EF Macro and
4. 180mm f/3.5L EF Macro.

Sigma is the only independent lens maker that offers a wide range of lens selections, including macro lenses. Currently, there are three macro lenses offered by Sigma:

1. 50mm f/2.8 EX Macro,
2. 105mm f/2.8 EX Macro and
3. 180mm f/3.5 EX APO HSM Macro.

All three provide close focus down to 1:1 life-size without using any accessories.

I acquired the Sigma 50mm f/2.8 EX Macro lens, which came with a couple of Nikon manual-focus lenses that I bought early this year. It is in mint condition and comes complete in box. According to the lens serial number, it appears to be among an earlier production, with a low serial number 1001019; that is, if the serial number begins with 1000000.

Lens Construction, Mount Availability and Compatibility

The Sigma 50mm f/2.8 EX Macro is available in a number of mounts for most major makes of 35mm SLR cameras. These include Canon, Minolta, Nikon (D), Pentax, and Sigma’s own 35mm SLR camera bodies.

For Nikon camera, Sigma 50mm f/2.8 EX Macro is a D-type lens. It is compatible with Nikon’s advanced 3D matrix metering system or 3D color matrix metering of Nikon F5 or D1 series. It has a special designation D for Nikon system, with 50mm 1:2.8D Macro written on the barrel.

Manufacturer’s specifications: Sigma 50mm f/2.8 EX Macro 1:1

Mount: Canon, Minolta, Nikon(D), Pentax, Sigma
Lens Construction: 10 elements in 9 groups (10/9)
Number of Blades in diaphragm: 7
Aperture Range: f/2.8-f/32
Minimum Focusing Distance: 7.4 inches
Magnification: 1:1 (one-to-one life size on film)
Filter Size: 55mm
Hood: Screw-in hood
Dimension: 2.8 x 2.5 inches
Weight: 11.3 ounces

Physical Appearance, Built, Handling, Features and Operations

In terms of physical appearance, Sigma is larger than the Micro-Nikkor 55mm f/2.8. It is a tad (just a couple of ounces) heavier than Nikon, and uses 55mm filter thread in contrast to 52mm used by Nikon 55mm f/2.8 AIS lens.

The lens has a focus limiter switch (Limit and Full). In FULL mode, the lens will focus from 0.188 m (7.4 inches) to infinity. A focus ratio (or magnification) is marked on the front tube, with white and legible markings between 1:5 to 1:1. In the LIMIT mode, the lens will restrict a focus distance in between 0.188 m to 0.24 m, which is roughly between 1:1 to 1:2 magnification. The lens allows close focusing to one-to-one life-size magnification, producing real life-size on film, without using any accessory.

There is a tidy-bit problem with the focusing. Virtually all (modern) Nikon AF cameras are equipped with an AF focus indicator in the viewfinder with arrows in both directions to inform the user which direction to manually turn the lens’ focus ring to achieve focus in manual focus mode. The Sigma lens has a focus ring that turns in opposite direction (counter-clock wise to infinity) in contrast to Nikon lenses (clock-wise rotation). And therefore the focus arrow indicator in the viewfinder cannot be used as guidance, because the focus ring must be rotated in opposite direction to the arrow. If there is one incompatibility of the Sigma lens in Nikon system, this is it. It is an insignificant problem and no problem at all if the lens is used in autofocus mode. However, in manual focus mode it is quite annoying to me.

The front barrel does not rotate during focusing, a very useful feature for using a polarizing filter. But, in my opinion, the lens uses the “wrong” filter size (55mm). I do not have any filters in this size. So I had to get a step-down filter ring (55-52mm) to make accessible the use of my Tiffen 52mm circular polarizing filter.

There is a price to pay for doing this. The Sigma 50mm f/2.8D EX Macro has a screw-in lens hood, and should be used at all times. With the 55-52mm step-down filter ring, this hood cannot be mounted onto the lens. The front optical element is a bit recessed, but not deep enough to shoot without the hood to avoid flare. I have a cheap collapsible rubber lens shade that I can use on this lens. If you think you will get this lens, I would suggest getting a 55mm filter set for the lens, so that its strong metal lens shade can still be used to control flare. For me, it is cheaper to get the step-down ring than another set of filters.

The lens handles very well, with its metal construction and all around the body, despite its lightweight feel. This is the EX lens in the Sigma line of professional lenses designated by a golden ring, with metal barrel and nice exterior crinkle coating. The lens feels very solid, but not absolute solid compared to my Micro-Nikkor 55mm f/2.8 lens. There is no depth of field scale, except an aperture f/32 marked on the barrel. Distance scales in meters and feet are marked on the focus ring. The focus ring appears to be smooth with good action, but it makes a scratchy sound that makes me feel like the ring has a rough (non-smooth) turn.

Autofocus is fast and reasonably quiet, but it definitely depends on the camera body. I have tried this lens on Nikon F4 and F5. With the F4, it is a bit slow and loud. With F5, it is very fast and quiet. As usual, for a macro lens, autofocus is slow from minimum focusing distance to infinity. The focus ring has to turn almost 3/4 revolution (~ 270 degrees) around the barrel.

Optical Performance

During the summer and fall of this year, I have used the Sigma 50mm f/2.8 Macro as a standard lens for my nature photography (in place of my usual Nikon 55mm lens). By habit, I always operate the camera and lens in manual focus mode. The lens performed exceptionally well, mechanically and optically; I am impressed!

After using this lens in the field, I wanted to see how good it performs optically in the macro mode. So I decided to conduct a simple test and compare its result to my Nikon 55mm f/2.8 AIS Micro-Nikkor. I have chosen a peacock feather for the subject, with a white cloth for the background to help me see the detail of the feather. Focus distance was set at about 1:2 ratio for both lenses.

The colored pattern of the peacock feather is dark blue (or black) in the center (shaped like the two eyes of a fly), then followed by a blue pattern encircling it. Next is the brown color, followed by green color, mixed with blue partially with yellow and then spreads out with green, yellowish-green and gray, etc. The peacock feather fills the whole frame and spreads out almost flat, making it possible to examine sharpness at the center as well as at the corners on the film plane.

Even though there is a slight difference in focal length (that is by 5mm between 55mm and 50mm), I notice quite a dramatic difference in image ratio produced by the two lenses. It appears that the Sigma decreases in focal length quite significantly at close range, that is, in macro setting, producing a much smaller image compared to Nikon 55mm. Therefore, image quality produced by the two lenses may not be adequately compared for a justifiable conclusion.

But I did it anyway. I mounted my camera fixed on the tripod (so I only needed to change lenses), shot with both lenses in aperture setting: f/3.5, f/5.6, f/8, f/11 and f/16. Why f/3.5 and not f/2.8 or f/4? Well, for some reason, my Nikon F4 does not register favorable exposure at f/2.8. But I got consistent ready for both lenses at around f/3.5 (this aperture is an estimate, though). So I decided to shoot at f/3.5. As usual, I always use my favorite color slide film Fujichrome Velvia for consistency in exposure and color. Due to its extreme narrow exposure latitude, I am also confident that any slight flaw attributed by the lens will show on the film. The resulting images are viewed using an 8x loupe on a lightbox.

Result and Comparison at Close Range
It is very difficult to distinguish center sharpness between the two lenses even at f/3.5. However, Sigma indicates a small amount of softness that quickly spreads to the corners, much wider than Nikon does. Nikon only shows a small bit of softness just at the corners. In other words, Nikon performs better than Sigma at wider aperture.

In terms of color, Sigma seems to produce a slightly warmer tone; a dominant yellowish color is perhaps a better description. Its color is not as deep or as rich as Nikon. For example, the green color of the peacock shows a richer green produced by Nikon. A close inspection reveals that color produced by Nikon 55mm lens is more vibrant and much richer than Sigma, particularly its superb contrast. Sigma appears to be a little bit pale overall—a signature of low contrast—with a touch of warm or yellowish color. I personally like the color produced by Nikon.

At apertures of f/5.6, f/8, f/11 and f/16, there is no distinction in image sharpness between these two lenses; sharpness is maintained throughout the entire film plane. As is expected of a macro lens, a flat field reproduction is assured by its center-to-corner sharpness, perfect for copying a document or photographing a flat subject. Sigma is at it best performance at these apertures. But again, while holding its super sharp images at these apertures, Nikon produces a richer color throughout its aperture with superior contrast at f/11 and f/16. Sigma shows sign of improvement by f/11 and f/16, but still produces warmer color.

There is indication of decreasing in sharpness at f/22. Its minimum aperture is f/32, and I suspect it will decline in optical quality even further. At a smaller aperture, it generally suffers from diffraction, light fall-off and softness even near the center. I would stay away from f/32 or smaller aperture.

With this lens, you can shoot at any aperture between f/4 and f/16 and will be assured of top image quality. You can even shoot at f/2.8 wide open and still get excellent results.

Result at Normal Shooting Distances
It is commonly understood that a macro lens only performs well in the macro range. In general, this notion is not true, and is often a misleading perception. A good macro lens is able to produce outstanding images, both sharpness and brilliant color, at any shooting distances. The Nikon AF Micro-Nikkor 60mm f/2.8D is a prime example, and is so eloquently described by Dave Burckhard (the LEAD in electronics) here at epinions (member: sweeper).

I have produced about 40-50 slide images with the Sigma used as a normal lens. And I am impressed with the quality of images—sharpness, color and contrast—it has produced. It is a fine example of a high quality lens. It is equally sharp optically in normal shooting distances as well as in macro.

Optical Flaw…if any
Light fall-off is visible at f/2.8, only a slight indication though. It is completely gone by f/4. I cannot detect any linear distortion on this lens. It is therefore optically well corrected.

Flare is very well controlled with its strong and nice looking metal hood. With a 55-52mm step-down ring, I cannot stack filters, or vignetting will occur. This lens does not appear to produce a true 50mm focal length, perhaps due to its macro capability and built-in tube. According to Sigma specifications, it has an angle of view of 46.8 degrees, slightly wider (almost one degree bigger) than a normal 50mm fixed-focal length lens (46 degrees). This might explain why my Nikon 55mm lens produces a much larger image at the same focusing distance.

There is no evidence of internal flare or ghosting when a bright object (like the sun) is in the frame. But for extreme brightness of the sun, I can still see a small indication, although not a weakness of this lens. It clearly performs much better than any zooms set at this focal range. It handles backlit subjects very well, too.

The Versatility of a Macro Lens

What is the difference between the Sigma 50mm f/2.8 Macro lens and a normal 50mm lens? Normally, a fixed-focal length 50mm lens is equipped with a wider aperture of f/1.8 or f/1.4. Being a standard lens, a 50mm lens is limited to close focusing distance at around 0.5 meters or 1.5 feet, not feasible for macro photography. With an aperture of f/1.8 or f/1.4, the standard lens offers a brighter viewfinder. But how often do you shoot the lens at its maximum aperture of f/1.4 or f/2?

The Sigma 50mm f/2.8 Macro, even though it is 2 stops slower than the 50mm f/1.4, still produces a bright viewfinder. In fact, all professional zoom lenses come with this standard f/stop of f/2.8. The difference in f/stop may not be the difference at all if you do not normally shoot at f/1.4 or f/2. The superb optics of your 50mm f/1.4 lens is not at its widest aperture. You would have to stop down to at least f/4. The major difference between the standard 50mm lens and the Sigma 50mm Macro is now apparent. The Sigma 50mm Macro can do everything that a standard 50mm lens can, plus it has a built-in tube allowing for close focusing. The Sigma has a floating focus mechanism (much like Nikon CRC—Close Range Correction) that helps achieve excellent image quality throughout its focus range from infinity down to 1:1 magnification at about 7 inches.

The versatility of the Sigma 50mm f/2.8 Macro manifests itself. It produces top image quality and operates like any normal lens you have. This makes Sigma 50mm f/2.8 or any macro lens (such as Canon 50mm f/2.5, Minolta 50mm f/2.8, Nikon 60mm f/2.8 or Pentax 50mm f/2.8) an excellent choice in your camera bag.

Recommendation

If you plan to own a 50mm fixed-focal length lens, I would highly recommend you get a macro lens instead. The advantage of a wider aperture offered by a standard 50mm lens, in my opinion, is not worth it in the long run. A macro lens is optically corrected to produce superior image quality for flat-field reproduction. I often use my Nikon 55mm macro lens to photograph old pictures that I no longer have their negatives. With modern-day technology, of course we can do a flatbed scan of old photographs. However, I require a negative of an image. With a macro lens, this can be done, and usually with superior results.

Currently, Sigma 50mm f/2.8 Macro lens costs somewhere between $230-$260. Being an independent lens maker that presumably offers an alternative lens at a cheaper price (as opposed to Canon or Nikon macro lens), the Sigma 50mm f/2.8 does not appear to present a much attractive competition.

If you use Canon system, its 50mm f/2.5 EF macro lens costs about $200-$250. If you are using Nikon system its Micro-Nikkor 60mm f/2.8D is selling somewhere between $300-$360. The extra high price on the Nikon is perhaps due to the 10mm increase in focal length, which we should factor in. I have never used the Canon 50mm f/2.5 EF Macro lens. So I cannot offer any solid opinion. But normally, a lens produced by a camera’s manufacturer is almost always superior to an independent lens maker. Therefore, for users of Canon system, the Sigma 50mm f/2.8 Macro lens does not offer much for a bargain. But if you can find one that is much cheaper than even $200, get it!

The price of the Sigma is one factor that I did not give this lens a 5-star rating. For optical quality, it rightly deserves 5 stars. For those of us who are looking for an alternative lens at a cheaper price, the Sigma 50mm f/2.8 lens does not offer much room for making a purchasing decision. The following lists my opinions about the Sigma lens.

PROS
1. Produces top optical quality
2. Excellent built
3. Offers close focusing down to 1:1 magnification

Cons
1. Not much cheaper than Canon or Nikon macro lens
2. Uses 55mm filter size (in my opinion, the wrong size)