Need help with Kenko Extension tubes

[ddkphotos]

I got a set yeseterday - and have been playing around.
Here are some of the better ones:

http://ddkphotos.smugmug.com/gallery/2314180

I have about a thousand questions. But let's start with a few...
I'm sorry if they've all been asked before...
My set up is on a canon rebel xti - 50 mm 1.8 lens - kenko set of 3 extension tubes - played around with several or singles... on a tripod - using wireless remote to trigger shutter. Most of them were taken in my shooting cube...

1. I'm finding it hard to see through my viewfinder well enough to tell if the focus is where I want it to be... After my first tries yesterday, I adjusted today and upped my aperture to F22 -and playing around with the distance of the subject to the camera helps. But then I find it really hard to see if I've got it right... Actually it looks good on my lcd but then when I bring it to my computer I see that I'm off... (I wear glasses btw... blind as a bat without them)...

2. What about the little dust and specks of life! Man - this thing is picking up every single detail! Like the fuzz from the paper towel that was in the bowl with the cherries... The dust on the chain locks... Any tips on avoiding that?

Let's start with those. If anyone has any tips on how to use these it would be greatly appreciated.
(PS: I don't have any other lenses and am not about to buy any more seeing I just bought the camera!)...

[Old Timer]

Here is the first place to go for general answers.

Extension Tubes - Full Disclosure

Then I suggest addressing question directly to Loupey he is the "Tube Guru". I use them but am not nearly as technical as he is.

[another view]

That's a great thread, must have missed it before. It really shows what you can do with a set of tubes. I've used them a couple of times and won't call myself an expert but:

Exposure will change with extension, this is true with large format cameras too - some optical physics at work here. There are complicated mathematical formulas that you can use, or with digital you can just use the histogram - I won't tell... Focus with the lens wide open (maximum aperture) so the viewfinder is as bright as it can be, and then stop down to whatever you're going to use for your shot. As you have probably figured out, even f22 doesn't give you a ton of DOF. Great job on the images though!

Dust is a real hassle, and more magnification just makes it look bigger! I use my Giottos blower (same one I use to clean the sensor) after I've used windex and a towel, etc. Still, a lot of times I end up cloning out a piece or two in Photoshop...

[ddkphotos]

Thanks Old Timer - I read that yesterday... And thanks to you too Another view... I appreciate you looking and your feedback... I guess I'll get a little blower...
How come no one uses their first name around here?
Diane

[Loupey]

Man those images are great! For just getting them yesterday, I'd say you don't need much help. Very prolific indeed! Terrific textures and colors.

I think your only real question here is controlling the shallow DOF. When you say your viewfinder is dark, I'm assuming its when you are pushing your DOF preview button (which, at f/22, it's gonna look black). It is true that the more extension you add, the more light you lose. But even with all three tubes on a 50mm f/1.8, your viewfinder should still be bright enough when focusing.

Hate to ask this but you are using manual focusing right? Focusing has to be right where you need it. For still lifes and studio work, I recommend using a focusing rack. It allows you to move the camera back and forth to focus as opposed to using the focusing ring. Much more precise.

Your technique sounds good. Check your shutter speed - avoid speeds between 1/4s to 1/60s (vibration is most visible at these speeds). If necessary, add a neutral density filter to go under these speeds to minimize the vibration effect (lets all face it - NO tripod clamped however tight is going to eliminate ALL vibration). For the examples you listed, I would recommend something like 2 to 4 seconds in the f/11 to f/32 range.

Hope that helps! Sorry but I can't help much in the still lifes/studio department. I'm your opposite in that respect (working with non-still lifes / outdoors )

[ddkphotos]

Thanks Loupey! I appreciate you taking the time.
Yes I'm using manual focus. It's not that the viewfinder is dark - and no I'm not pressing the DOF button - it's just really hard to tell if the focus is right where I want it... I can tell if nothing is in focus - but I'm having difficulty seeing if the focus is in the right place... Hard to explain.
Some of these are taken at way slower than 1/4... all at F22 - and the slowest I think was like 3 seconds... Wireless remote - so I'm not touching the camera - but still - the mirror causes some movement - no? Are you saying camera movement is worse from 1/4 to 1/60 but then gets better as you go slower?
Hey - I love the non-still lives outdoors too - they're my favorites!!!

[Loupey]

... Wireless remote - so I'm not touching the camera - but still - the mirror causes some movement - no? Are you saying camera movement is worse from 1/4 to 1/60 but then gets better as you go slower?

Yes, exactly (well sort of)! The mirror and shutter produce a given amount of internal vibration regardless of whether your shutter speed is 1/2000s or 20 seconds. By using a slow shutter speed like 2 seconds, you are minimizing the effect of this vibration (percentage of time during exposure) because the natural frequency of a camera body is higher and will dampen out quickly - leaving the remaining 1.97 seconds (using 1/30s as a comparative example) that the shutter is open vibration free.

In other words, if it takes your camera 1/30s for the vibrations to die out, shooting at 1/30s would be the worst thing you can do as it will record the complete wobble. Shooting at longer and longer shutter speeds will allow that same wobble that you caught to be "overwritten" by a stronger, stable image. The wobble is still there, just very faint.

The focus issue then is with your subject matter. Your subjects seem to be round. Selecting a specific focus plane through a sphere is probably the hardest to guage. Try more examples like the tea bag and you'll find it easier going.

[another view]

How come no one uses their first name around here?

That is my real name, my parents were wierd.








Just kidding.
Steve

[ddkphotos]

LOL Steve!

[another view]

Yes, exactly (well sort of)!

The other day I was thinking about how a lot of times the answers to questions are "it depends"... There are no absolute rules, but Loupey has done a great job with his examples and explainations. Like I said, I haven't done much with tubes but regarding the 1/4 - 1/30 being the shutter speeds to try to avoid, I agree.

But then, it depends... There may be some compelling reason to use a shutter speed in that range, and if there is then it's probably more important than avoiding it - especially if you're careful as you are with the wireless remote. This is true for any shot. If you're trying to convey a sense of motion and 1/15 is the right speed, then that's the one to use - although total sharpness doesn't usually apply with motion, so bad example. You get the idea...

[mn shutterbug]

All right, time to revisit this thread, now that spring is around the corner. I noticed, after rereading all the replies, that a few members were going out and buying extension tubes. I'd love to see results from the tubes with technical info.

[Frog]

Don't know how I missed this.....oh its a year old.
Anyway glad you bumped it up, Mike. I would have kept trying to get faster shutter speeds to eliminate vibration.