Monday, 26 May 2014

A test of Vivitar extension tubes for macro photography with a Nikon d5200

The following test was conducted to familiarise myself with the Vivitar extension tube set when used on my Nikon d5200. I thought the results might be useful for you too. The Vivitar macro extension tube set contains three elements, giving an extension of 12 mm, 20 mm and 36 mm. They can be used in combination to give a maximum extension tube length of 68 mm. they have electrical connections which allowed me to use my Nikkor 18 to 55 mm and 55 to 200 mm lenses, theoretically allowing autofocus and aperture control.



I used a Daisy as the test subject and the one I chose was 20 mm in diameter across the flower. The camera was mounted on a tripod and I used the extension rings in increasing lengths through the series: no extension tube, 12 mm, 20 mm, 32 mm, 36 mm, 48 mm, 56 mm, 68 mm.

I set the camera to fixed aperture control at F5 .6. and deliberately focused the lenses manually. Several pictures (between three and 20) were taken to capture the focus of the flower from the closest to the furthest distance from the camera.

I captured raw images, optimised for contrast and produced JPEGs. In the first series of images in this article, I combined all the different focus shots into a focus stack using Helicon Focus Pro software. In the second series of images in this article, I chose an image with one point of focus on the flower and cropped it so that you can see the change in depth of field (depth of focus) with increasing extension tube length.

All images are also available to view in larger format at https://picasaweb.google.com/107595387761034666575/TestOfExtensionTubesWithNikonCameraMagnificationAndFocalDepth

Stacked focus images with increasing tube length.


Nikkor 18mm – 55mm lens, set at 55 mm:

hand held, in field, no extension tube

Nikkor 18-55mm lens, no extension tube = 1x

Nikkor 18-55mm lens, 12mm extension tube = 1.8x

Nikkor 18-55mm lens, 20mm extension tube = 2.2x

Nikkor 18-55mm lens, 32mm extension tube = 3.2x

Nikkor 18-55mm lens, 36mm extension tube = 3.4x

Nikkor 18-55mm lens, 48mm extension tube = 4.3x

Nikkor 18-55mm lens, 56mm extension tube = 4.8x

Nikkor 18-55mm lens, 68mm extension tube = 5.9x


Nikkor 55mm – 200mm lens, set at 200 mm:

Nikkor 55mm - 200mm lens, no extension tube = 1x

Nikkor 55mm - 200mm lens, 11mm extension tube = 1.3x

Nikkor 55mm - 200mm lens, 20mm extension tube = 1.5x

Nikkor 55mm - 200mm lens, 32mm extension tube = 1.9x

Nikkor 55mm - 200mm lens, 36mm extension tube = 2.0x

Nikkor 55mm - 200mm lens, 48mm extension tube = 2.4x

Nikkor 55mm - 200mm lens, 56mm extension tube = 2.5x

Nikkor 55mm - 200mm lens, 68mm extension tube = 2.8x


Without an extension tube, the Daisy head fills about one third of the screen width with the 18 to 55 mm lens. With the 20 mm extension tube, the Daisy is magnified two times and fills the height of the picture. The final magnification achieved at 68 mm extension tube is nearly sixfold. Theoretically you could reach even higher magnifications by using a shorter focal length. However the subject is then so close to the lens that it is shaded and difficult to illuminate with natural lighting.

For the 200 mm lens, the Daisy fills about 1/5 of the image width without any extension tubes and the image is magnified to a maximum of 2.8 times by the time you use the 68 mm extension tube. Here you can increase the magnification by decreasing the focal length down to the minimum of 55 mm or anywhere inbetween.


Single focus images with increasing tube length.


Nikkor 18mm – 55mm lens, set at 55 mm:

Nikkor 18-55mm lens, no extension tube

Nikkor 18-55mm lens, 12mm extension tube

Nikkor 18-55mm lens, 20mm extension tube

Nikkor 18-55mm lens, 32mm extension tube

Nikkor 18-55mm lens, 36mm extension tube

Nikkor 18-55mm lens, 48mm extension tube

Nikkor 18-55mm lens, 56mm extension tube

Nikkor 18-55mm lens, 68mm extension tube


Nikkor 55mm – 200mm lens, set at 200 mm:

Nikkor 55mm - 200mm lens, no extension tube (camera shake!)

Nikkor 55mm - 200mm lens, 11mm extension tube

Nikkor 55mm - 200mm lens, 20mm extension tube

Nikkor 55mm - 200mm lens, 32mm extension tube

Nikkor 55mm - 200mm lens, 36mm extension tube

Nikkor 55mm - 200mm lens, 48mm extension tube

Nikkor 55mm - 200mm lens, 56mm extension tube

Nikkor 55mm - 200mm lens, 68mm extension tube


These image series clearly demonstrate how your depth of field (depth of focus) decreases with increasing image size. This holds true if you start with the smallest image taken with the 200 mm lens through to the largest image taken with the 55 mm lens plus extension tubes.

The heights difference between the base of the Daisy in the top is about 3 mm. With the 55 lens, you just about have everything still in focus with the 12 mm extension tube if you set the focus point about halfway between top and bottom. With wider extension tubes you then have to think about choosing what you would like to have in focus or photographing a series of focus slices that could be combined in focus stack. With standard pictures, changing aperture size down to f11 or further does give you a greater depth of field. However the effect is minimal when you are photographing so close to the subject, so it’s better to keep the aperture open and let more light in.

If you need to take a picture quickly, with a high degree of focal depth, I recommend using a compact camera on its macro setting. As you can see below, you can achieve good results this way too.

Daisy taken with macro setting on Olympus fe compact camera


Conclusions


I found the Vivitar extension tubes easy to use. For really close macro work, I recommend using a tripod and taking pictures at different focus through the subject. If you have an external release cable, use that to avoid camera shake. Otherwise, either use the timer control or the timed multiple exposure setting, taking a series of pictures at about three second intervals, which allows you to manually adjust the focus in steps.

Out in the field, I’d probably use the 55mm-200 mm lens for handheld shots at intermediate focal lengths. From past experience, I would use a fixed focus and take multiple exposures.

For quick photography where a high depth of field is required, I would use my compact camera instead.

Reference: for Depth of Field technical calculations: 

http://en.wikipedia.org/wiki/Depth_of_field

2 comments:

Google