I am reading post's here on the forum talking about using extension tubes. Are the benefits only allowing you to take/get closer shots?
What are the downsides? Are images softer? Do you see integrity issues when enlarging prints?
I currently have the Mark IV with the 300 IS 2.8 / 1.4x converter.
Extension tubes effectively reduce the minimum focus distance of a lens so you can get closer and therefore get the subject larger in the frame. They also give you an additional small degree of magnification even at the same distance compared to the same lens without the extension tube. There are no optical components, so they have no effect on image quality. The disadvantages are that you lose some light (i.e. have to increase exposure) and you lose the ability to focus at longer distances.
I appreciate the clarification!! Thanks
Great explanation Mike ... can add you can stack the tubes for using more than one, they come in 12 and 25mm The Canon Tubes are a little more expensive but made out of metal. When staking three with a Mk4 there will be some bending using plastic tubes. Normally I carry three 25.
Wow 3 25's? with what lens or does it matter? I may have to look into this :)
I too have a Canon 25mm tube (mark II), and I'm fairly sure it's not made of metal. Looks like some kind of rigid plastic/polymer, but yes, the mounts are most certainly metal & I doubt they would flex, even with 2-3 stacked together.Originally Posted by Alfred Forns
Also, I read an article recently that clearly implies that tubes do degrade IQ, especially when used on a non-macro lens which is not optimized to work at or near it's close focus limit.
http://nocroppingzone.blogspot.com/2...p-filters.html
The thinking there is that close-up filters like Canon's 500D are better in terms of both light loss (none) and maintaining good IQ.
Just thought I'd throw this into the mix, as I'd be interested in what users have actually found from personal experience when using tubes. I suppose if you start off using a high quality prime the trade-off in IQ loss might be worth it if not too noticeable?
Steve
Last edited by SteveClifton; 06-17-2010 at 01:21 PM.
Steve the Canon 500D is hard to use and limits distance to subject, best to try and find for yourself. I have one and only take when there is no macro lens around. Not a substitute for tubes. Just talking form personal observation but not sure how can the 500D have better image quality?
Degrading image wise I imagine there could be some ( ???) but its mostly theory. Highly suggest having some around all the time ... even use with my 500 lens.
Steve,
I agree with Alfred. I've tried the 500D type add-on lenses and found them not that great. The extension tubes can certainly get a lens out of its design specs, commonly with increased spherical aberration. But with extension tubes, you are typically trying for higher magnification (duh) which results in shallow depth of field, so you tend to use small apertures. That mitigates the loss in quality and one is commonly diffraction limited, at least in my experience.
Roger
Thanks to both of you Alfred & Roger for your personal insights into this. Alfred, this is why I never bought a a 500D as I thought I would find limited opportunities to use it (it's not often that your subject is roughly 1/2 metre in front of the lens afterall!) Even with the 25mm tube the restricted range of min-max focus can be a pain, especially if a bird presents itself once fitted.
Roger, looks like it's one of those cases where practice wins out over theory. I will probably eventually buy more tubes to get more flexibility, as even one 25mm makes a relatively small difference to the minimum focus distance of my Sigma 180 Macro (with a small increase in magnification too). The impact on my 100-400L is much more dramatic and increases its versatility even further.
Steve
Last edited by SteveClifton; 06-18-2010 at 06:06 PM.
Many years ago I used to use bellows to place my lens way out beyond the normal minimum focus distance. I can't imagine that putting a 12 or 25 mm extension tube (even the two stacked) between a 500 mm lens and the body would do anything noticeable to image quality.
On the other hand, I may be wrong.
Last edited by John Chardine; 06-18-2010 at 07:47 PM. Reason: typo
I am getting the 800mm from Canon for a couple of weeks and want to take it out with some extension tubes. I appreciate the feedback and look forward to posting results. I am taking the family to the WildAnimal Park here in Escondido and then will be taking the lens to Bolsa Chica.
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