Extension Tube

[justin_koenigshof]

<p>Hello all,<br>

I was reading about extension tubes in Bryan Peterson's "Understanding Exposure" and am curious if anyone uses them quite often. This was the first time I had heard of extension tubes to get closer to your subject without having a stronger lens and without physically moving closer to your subject. Do they make specific types of tubes for different brands of cameras or are they all universal? Is there anything I should know about extension tubes that could affect my photos such as losing sharpness in my photos? <br>

Any information on extension tubes would be appreciated. Thanks!<br>

Justin</p>

[tommyinca]

<p>If you do higher magnification macro (ie: > 5:1), extension ring, tube and bellow are more of a requirement then an option. </p>

<p>You still need to get closer with extension tube for higher magnification. The only way not get closer and still gain higher magnification is with the increase in the lens' focal length. You do get less closer with extension tube then using diopter (aka: close up lens). </p>

<p>Auto (ie: aperture, electronics) extension are mount specific. The manual one can be interchangeable with proper adapter. </p>

<p>You do lose sharpness with extension even there are no optics in-between the lens and sensor. This come from change of back focus length which reduce the effectiveness of optics that are designed to correct all kinds of aberration. In addition, too much extension tube also can get the lens to function outside of its design parameter resulting in worst performance. There are instantes where adding teleconverter and/or close up lens can be more effective then using tube alone. </p>

[tommyinca]

<p>Here is a few extension tubes that could be of interest. Start from upper left , a Nikon K1 ring which is only 5.8mm in length. Great for wide angle lens close up. A Nikon PN-11 which is an extension ring with a tripod mount built-in, a light weight 90mm M39 manual extension tube. Its great for adding solid stable extension length without adding too much weight. From the 2nd row left, a Canon 25mm extension tube with lens electrical contacts, A pentax variable length extension with a helicoid and a Vivitar teleconverter with a variable extension tube built-in. </p><div></div>

[colin carron]

<p>All extension tubes do is allow you to increase the ditance between the lens and the camera film / sensor. This allows te lens to focus on objects closer than you would be able with the lens by itself. They are quite fun to play with to get really close shots. They are better than adding dioptre lenses at the front of the lens as they do not reduce image quality.</p>

<p>They are made to fit a specific camera / bayonet type. so for example the Canon cameras with the EF or EF-s bayonet would use the EF extension rings. The same for Nikon, Pentax etc.</p>

<p>They usually come in a variety of lengths and the longer ones allow you to focus closer. Be aware that as you get closer to an obkect the depth of field gets shallower so it is difficult to get everything in focus..</p>

[mike_earussi1]

<p>All lenses are designed for an optimum magnification range, but once beyond it (in this case, by using extension tubes) their image quality deteriorates, though how much depends on the lens. You also lose light via an increase in the aperture as the f stop # is determined by focal length divided by lens opening (the further the lens is from the "film" plane the greater its focal length becomes thereby increasing the f #).<br>

These drawbacks to extension tubes are some of the reasons that many choose close-up diopters over extension tubes (plus they also cost much less and take up much less room), since diopters work by altering the focal length of the lens instead. Of course they also introduce their own "flaws," primarily much poorer corner resolution and a possible increase in flair since most brands are uncoated. But the center does remain sharp which is the area most are interested in in the first place.</p>

[tommyinca]

<p>Here is an example of how too much extension can reduce image quality. Below is a shot of an un-interesting bar code from a small Nikon filter box. Taken with a Canon EF50/1.4 on a 5D body. This is one of my better lens out of many but in this example it has been push out of it designed optimum performance range (on purpose) for comparison. I put a Kenko 36mm extension tube on it (yielding about 1:1.6, or 0.65X). See lower right for a 100% crop of the area near the red arrow. On the lower left is another 100% crop. This was from the same 50/1.4 lens but in place of a 36mm tube, a Kenko 1.5X TC plus a Canon 450 (+4 close up lens) diopter and a less aggressive 12.5mm extension tube was used. Pictures from both crops have MLU, flash and tripod. You can see ink jet print dot and some micro paper texture on the Kenko+450 crop version. There were also some CA (likely from the cheap TC) but it can be easily corrected by ACR RAW conversion (if choose to, I didn't). The crop with the 36mm extension tube was beyond help. One thing to add, if a 25mm tube was used instead of the 36mm (less magnification but stay inside the optimum range), the EF50/1.4 yield good if not better result then the TC and close up lens combo. This example is just to show, no optics does not equal to no performance lose. Also nothing wrong, about the EF50/1.4, it is just that it was push out of it performance envelop.</p>

<p> </p><div></div>

[justin_koenigshof]

<p>Thanks Tommy for the excellent explanations and images! I'm a very visual learner and these help me quite a bit. It seems as though it would be better to just use a diopter and a small extension tube. When it comes to diopters, what kind of price range are we typically talking? </p>

[tommyinca]

<p>What lens do you plan to use it with and the type of picture you plan. Close up lens' (aka: diopter) price range and as well as quality can go all over the place. They can range from $5 to few hundreds dollars (ie: fancy brand name such as century optics, some Leica). Like any optical elements both workmanship quality and design do matter. They are not all the same and its the best to buy what fit the current lens you already have. After all, close up lens and extension tube are means to save some $. If you end up buying everything new, you won't save much from a macro lens.</p>

[plasma181]

<p>I have used tubes with fairly good luck. You focus by moving the whole camera back and forth.</p>

<p><a href="http://www.photo.net/photo/2934172">http://www.photo.net/photo/2934172</a> </p>