Lens review – A classic put to the acid test


Some days ago SIGMA announced four new lenses on their website and on different company-owned social media pages. So before taking a closer look at these newcomers made of glass, I recently became interested in reviewing the classic that by now can’t be neglected anymore, the SIGMA Art 35mm f/1.4 DG HSM lens, in terms of autofocus and vignetting and with studio photography.

Autofocus:

The autofocus (AF) is measured in a camera’s body while the engine is located in the lens. The autofocus can be readjusted. The camera should recognize every kind of subject automatically and then apply the correction mode. However, every lens has stronger or weaker deviations in its autofocus. This can relate to the front or the back focus. This means that the autofocus operates too much ahead or too much to the back. This can be amended and thus improved on most cameras.

By doing an AF test you can check whether the autofocus works correctly. Therefore you need to take some contrasting pictures and direct your camera as far as possible to the parallel side of the field you want to capture. For this purpose the company LensAlign produces specific equipment in order to do such tests.

For this test shooting with an open aperture is recommended since this will reduce the focal plane. The AF test was carried out with natural diffuse light. The tripods were set up at a certain distance that was predefined by LensAlign. In this case the photo was taken with an APSC camera and a lens with a fixed focal length of 35mm. The distance was 1.5 meters. On both tripods a panel with a tiltable scale and a camera were fixed. It is important to direct your sensor to the parallel side of the panel. For the appropriate setting a hole in the middle of the panel is required. Behind this hole you can see a red spot if the angle is the right one. The hole will be closed after the completed exact setup.

The next step is to take three photos with an open aperture. In this case with f/1.4. When doing so, mind using an ISO value as low as possible and fast shutter speed that will guarantee a picture of the panel under the best conditions.

While doing this test I found out that my camera, the Canon EOS 600D, in combination with the SIGMA Art 35mm lens focuses a bit on the front. Of course, this can vary depending on the combination of your camera and lens. However, in any case you should readjust later in order to use the autofocus perfectly.

But this isn’t possible with every camera. So it’s necessary to study the manual carefully as it will give you more information on this. It’s almost always the case though that lenses have a front and a back focus without corrections adjusted to the camera. You can notice that, for instance, when shooting with an open aperture and when the focal plane isn’t located on the spot you’ve been focusing.

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Testing vignetting

When people talk about vignetting in photography, they refer to an existent luminance reduction.  This becomes visible by shading the photo to the edges of the picture. Vignetting occurs especially when shooting with an open aperture and it counts among common imaging errors. However, you can amend vignetting digitally or avoid it by dimming while taking pictures.

Many modern cameras also have the option of brightening vignetting automatically. In this test, however, this configuration was deactivated. The camera is set up for normal exposure mode. In the next step a photo is taken of the projection surface of the operating overhead projector. First, a picture is taken with an open aperture of f/1.4, then you repeat this procedure with a critical aperture of f/4.

The photos are then exported as tiff-format files in a photo editing program. With software by MAtLAB Handle Graphic the pictures are uploaded one by one. Luminance reduction is graphically displayed in two different diagrams. An additional working tool in this case was the Canon EOS 600D besides the SIGMA Art 35mm f/1.4 DG HSM lens.

The result of this test was that the lens has some minor luminance reduction. The evaluation in this case clearly proves the quality of the lens claimed by SIGMA. Luminance reduction can be post-edited very easily.

Test results:

Open aperture f/1.4

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Critical aperture f/4.0

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Shooting in the studio

I enjoy using the Art lens not only when taking portraits but also for doing documentary photography such as street photography, even if in this case I often have to get used to the limited focal length of 35mm. But even in the studio it’s my everyday companion. Depending on your subject in studio photography you usually rely on longer focal lengths, for shooting portraits that’s usually 50mm at least. But also for still-life photography you basically use long focal lengths.

Well… Sometimes I simply don’t want to renounce the wonderful quality of the 35mm lens and keep enjoying the brilliance of the photos it creates. For this reason only recently I put it on my camera after building a smaller set of colorful smoothies in order to start a frozen-liquid test in between. This means shooting liquids with high-speed in order to make them look like frozen in the pictures.

Just take a look for yourselves at the photos… Trying this out was great fun. Unfortunately, sometimes the splashes of the colorful smoothies didn’t turn out as sharp as I’d wished. But after the experiment I was still very happy with the result the SIGMA Art lens had provided in this situation.

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