• Photography: Macro Extension Tubes

    For a long time now, I've followed discussion of extension tubes for macro photography. And a few years ago, I looked up what they cost and quickly dismissed them. However, in the back of my mind, I kept thinking "what if those are really what I need to get these stellar macro shots?"

    Probably a year ago, I considered getting them again. I talked to someone that had them, and to someone else that had used some... one person said I could use the cheap plastic tubes (less than $10) and I'd be happy. The other person paid $200 for the Nikon brand specifically because it would pass the auto focus information from the camera to the lens itself. The cheap one would not, meaning all focus would be done manually. My eyes aren't young, and I wear corrective lenses daily. I was pretty sure I'd need the camera to focus on the subject more often than not. Plus I had huge concerns about an expensive macro lens connected to a cheap piece of plastic. What if it let go and my lens hit the ground?!

    I did more reading, specifically people's opinions and reviews. As one might expect, the consensus was all over the place. I asked some local club members if they had a set I could borrow to see how they worked, but no-one responded. I dismissed the idea and decided I didn't need the hassle.

    Last Sunday, I decided I had to have the extension tubes. My birthday was coming up, and I was committed to the process. Checking Amazon Prime, I found some inexpensive ones as well as the official Nikon set that was still the same price as it was years ago. As I checked the different brands, I made sure the part would fit on a Nikon D90. I read more reviews, trying to decide while heeding any warnings posted by other photographers. Shockingly, I saw some negative reviews of the Nikon set. I figured those would be tried and true, essentially bulletproof, "the" set to buy. They weren't as special as I'd thought, it seems. Why pay $200 for something you can do for $60, I mused. The Polaroid set listed all the same specifications, and after a few more deliberations it was added to my cart. Also added was a new rubber hood for the 50mm lens, a UV filter for the 72mm lens, and an off-shoe flash cable for the SB-800.

    The electrical contacts allow for Auto Exposure and Autofocus capabilities.

    The set consists of three tubes: 12mm, 20mm, and 36mm. You can use them one at a time, or join them together as desired in any combination -- including using all three at once. The tube moves the lens away from the body of the camera, creating a tighter focal point that is magnified accordingly. This thread contains more explanation of how it works, and includes some stunning images: http://www.reef2reef.com/forums/phot...cro-shots.html

    The tubes themselves don't feel flimsy. They fit onto the camera nicely, and lock into place with a solid click. I haven't noticed any flexing with the lens on, nor did I have to force it on. To install the extension tube, an arrow lines up with the white dot on the camera body. Turn to lock it into place until it clicks, just like you do with any lens.

    These tubes don't contain any glass. They are a locking bridge that binds the lens to the camera at an extended distance. The benefit of this particular set is that autofocus information is transmitted through the extension tubes.

    Some reviews mentioned how the metal unlock tab gets in the way of the lens release button, but it's not a problem with the Polaroid set of tubes. In addition, there are three and you can place them in any order you want. The 12mm is the one that sits closest to that button, while the 20mm and the 36mm leave plenty of room to unlock them from the camera body.

    The D90 weighs 1.4 lbs, and the 110m AF-S macro lens with the tubes weighs 2.6 lbs. Combined, it's 4 lbs. Thus it is heavy in your hands, and front heavy on a tripod. My tripod is a $10 flimsy item, not suited for this type of photography and I have to be cautious not to let it pivot forward all of a sudden during adjustments. On the other hand, the walkboard in front of my tank is a great surface to set the camera upon. I simply had to come with with a way to raise the camera to the proper height for some of my initial macro shots.

    Impulsively, I installed all three and aimed it at a coral. I saw nothing, pure blur. Part of this process is finding a subject that fits within the narrow focal range of the tube-extended lens. After using them for a couple of sessions, I'm learning which tubes are good for specific distances.

    Let me focus on one specific coral: the Leptastrea coral is on the sandbed, dead center in front of my tank about 3" from the glass. When I pointed the D90 with only the 110mm macro lens on said coral, it wouldn't focus until the lens was 8" away from the outer glass - which would be a freehand task or a tripod situation. For macro photography, a tripod is a must. Next I installed the 12mm extension tube between the body of the camera and the macro lens. For it to be able to focus on the subject, the lens measured 4" from the glass. When I added the 20mm tube to the 12mm, the distance shrunk to 3.5" from the glass, and when I had all three tubes combined (12mm + 20mm + 36mm), the lens was merely 3" from the glass. The macro lens has a hard hood that is 3" long, so it was butting against the glass and the Leptastrea was in focus.

    Measurements to the front glass:
    Macro lens alone - 8"
    + 12mm tube - 4"
    + 20mm tube - 3.5"
    + 36mm tube - 3"

    With extension tubes installed, the depth of field (DOF) is very narrow, a few millimeters wide. This requires a higher f/stop to increase DOF and include more subject in focus. Most of these shots were taken at ISO 200 with f/8, and the shutter speed was about 1/1000th. The lower the ISO, the less grainy the image - especially super magnified like this.

    I'm excited to be able to take such close macros, to be sure. The easiest ones are corals near the glass.

    All of these corals were along the front of my tank, so I tried each subject to find out what I could capture. The camera was set to 200 ISO, f/8 and I used the infrared remote to trigger each shot, after a 1 second delay as the mirror locks up. The flow in the tank was on, since this was a practice run. When using the extension tubes, less light gets into the sensor requiring the shutter to stay open longer. Any movement will result in blur, especially if the image takes a full second or more to be captured.

    Using only the 12mm tube or the 12mm+20mm tubes, I was able to focus on corals mid-tank, but didn't notice a big difference between a picture taken with the tube compared to an image taken without the tube. I'll have to really look at the images closely in Lightroom to see if there is any differences.

    Like anything, there is always more to learn if you reach for higher goals. Seeing other people's photography inspired me, wanting to be able to take better pictures and improve the skills I have now. And in time, I'd like to see the progress I've made. Do you feel similarly?
    This article was originally published in blog: Stacked extension tubes started by melev
    Comments 3 Comments
    1. Trido's Avatar
      Trido -
      What a coincidence. I borrowed the 100MM Canon macro lens from the college today, took a few pics and was wondering how to make them better. Thank you so much for sharing your experience with this. I guess I'll try 200 ISO instead of 32000 tomorrow. I went the wrong way.
    1. melev's Avatar
      melev -
      Yeah, 3200 or higher is too noisy.
    1. Alaska_Phil's Avatar
      Alaska_Phil -
      Thanks Marc. One more thing on my wish list.
      I wonder how it would work with my 300mm?