Kenko vs Canon Ext Tubes

[Lester Wareham]

I have the Kenko tubes but 3 times now the lens release has been accidently activated, this time my 300/f4 IS fell onto a sandy path with no rear cap on. The problem seems to be very weak spring on the kenko tubes release leaver.

The Canon TC lens release has a strong spring and I wonder if owners of both the Canon tubes and the Canon TC can conform the tubes have a similarly strong spring?

[ScottE]

I have used my Kenko tubes for a long time and have never had that happen. Either you got a defective tube or they have let quality slip in recent years.

[CyberDyneSystems]

Wow,. sorry to hear about that

Though I have not had similar problems with my set of Kenko,. my feeling has been that they are not tough enough for many of the applications I want to use them for.

Using with a 100mm macro on a 20D is no problem,. anything in that scale they are more than up to the task. I am NOT comfortable using them to hang the 1D mKII off of the back of a large prime however.. I need to get the Canons for this application.

The Canons, though costly, are in fact made to work with the heaviest cameras on the large lenses.. I'm sure they are up to the task.

[Greg_C]

Never had this problem with my Kenko tubes. Is it only one of them that is loose or do any of them do it?

[Lester Wareham]

Thanks for the feedback. All the springs seem to have the same strength so I guess this is as designed.

This has happened three times:

1. 12mm tube between EF 100mm Macro and EF 2X so I can use them together. 100mm macro fell off as I was focussing, fortunatly the MT-24 cables slowed its fall. This time I put it down to my hands getting in the way.

2. Whole stack in front of the EF 300/4. I noticed it was loose and relocked it in time to stop distaster. Not sure which tube in this case - possibly the 12mm again.

3. The one yesterday again with the EF 300/4 and only the 36mm tube. If it had dropped off earlier it would have landed in several inches of muddy marsh so I was lucky in a way. All cleaned up and seems OK but time will tell. I had the camera on my sholder at the time but in use my hand stays up near the focus ring with my two smallest fingures wrapped around the QR plate on the TMA foot, so the release leaver must have got caught on my clothes.

I just measured the force required to pull the leavers back using my wifes kitchen scales (don't tell her!), 50-100g with the 36mm being the weakest. The EF 1.4X measured as ~200g and the EX 2X as 300g and has a much less prominant leaver.

I presume the Canon tubes have the same sort of release leaver and spring strength and hope someone can confirm that.

I am reluctant to use the kenko tubes again after these events but don't want to bang out on Canon tubes if they are not an improvement in this respect.

[evandavies]

Just a longshot here as I don't have any extension tubes (I have a Kenko Pro1 x1.4 TC)

Can you shove a small piece of foam behind the release lever?

[Woolburr]

I have the Canon tubes EF 12 & 25 II and I can confirm that the locks on them are very very positive. There is no chance of an accidental release unless they wear very significantly.

[Lester Wareham]

Dan: thank you.

OK folks, I have sent off for the Canon tubes, it doesn't make sense for ~£1000 lenses to drop off the camera. The insurace may pay for it but it is more the down time. I am hoping my supplier will manage their normal same day dispatch.

Evan: As a stop gap I have some rubber bands around the release leavers.

[Woolburr]

I played with the Kenko tubes before I bought the Canon ones. I liked the price and 3 tubes vs. 2....but I didn't like the connection on the Kenko tubes...seemed sloppy to me, so I have Canon tubes.

[Lester Wareham]

Originally Posted by Woolburr

I played with the Kenko tubes before I bought the Canon ones. I liked the price and 3 tubes vs. 2....but I didn't like the connection on the Kenko tubes...seemed sloppy to me, so I have Canon tubes.

You are right they are rather loose, I could forgive that, but not the accidental release. At 1/3 price for a Canon set they were too atractive.

You buy cheap you buy twice I often say;

[BearLeeAlive]

I have used my Kenko tubes lots and have never had an issue. Yes, they have a wee bit of play but that never bothered anything.

I did get to try some Canon tubes and there is not doubt they are built better, things are also nice and tight. To get the full 68mm in Canon though was too much. I know ultimately you usually get what you pay for, and who knows, maybe I will have to replace my Kenko tubes someday.

[blackviolet]

i've never an issue with my kenco tubes, either. stacked with a 135 f2L doesn't present any issue.

[Lester Wareham]

The first of the Canon tubes has arrived.

To look at very similar to a Kenko tube, almost identical, similar leaver.

The leaver streangth spring is about 160-180g so 2-3 times as strong as the Kenko version.

The main difference is the amount of torque required to mount and dismount the lens. It is a lot less likely accidental movement of the leaver would cause the lens to unlock (I hope) as this would require considerable torque to be applied at the same time.

As has been observed by some on this thread the Canon tubes lockup tight with no obvious rotational or axial movement that I saw in the kenko tubes.

I think if you just use these Kenko tubes for the occasional shot you are unlikely to have a problem, but if you will be using a tube assembly all day, handling the equimpment a lot, different orientations, use of the stopdown preview, carrying the lens, and even with a smaller lens like the 100mm macro, this could be an issue.

Of course I can only comment on the Kenkos I have, not on others. I suggest care if the mounted lens at all loose.

Thanks to everyone for their input.

[CyberDyneSystems]

Well,. you'e definitely scared me into never trying the Kenko tubes with my heavy gear again..

My order for the Canon set will be soon.

Again,. very sorry about your lens,. I hope it comes out o-kay.

[Lester Wareham]

Originally Posted by CyberDyneSystems

Well,. you'e definitely scared me into never trying the Kenko tubes with my heavy gear again..

My order for the Canon set will be soon.

Again,. very sorry about your lens,. I hope it comes out o-kay.

Better safe than sorry I think.

Thanks CDS, the lens looks OK, no grinding noises when I focus. Fingers cross.