Extension Tube Focus Issues

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Jayceyned

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Evening everyone,

I'm a macro beginner & have been practicing some close up images of insects with a set of extension tubes & after a few weeks am still struggling to get any sharp images.

I'm shooting with all 3 tubes at speeds of around 1/125 & trying for f/8 - f/16 under natural daylight (no flash) using the standard 18-55mm & my 1000D. I'm generally at 55mm which let's me get a small spider to fill the frame.

I always make sure I use manual focus & move in & out and it's just occurred to me that I very rarely hear the focus confirm beep even when things appear sharp in the viewfinder, so I did a little test this eve using only 1 or 2 of the tubes & I get the focus confirmation a lot more often. Does this mean that with all 3 tubes, even though it looks sharp enough to me, the images are not actually in focus? Or could it be that the camera is just struggling with registering the focus at such large magnifications?

I just wondered if anyone else has experienced similar issues when using all 3 extension tubes and if anyone has any tips about getting sharper images at this magnification?

Could it be because of the lens I'm using ie. would it help if I were using a more telephoto lens and hence not having to be so physically close?

Any tips or insights would be gratefully received,

Thanks loads,

Jay.
 
I use my tubes on a 7d and 50mm. With the two smaller tunes I can get focus lock and beep but not with all three. if in manual focus I didn't think you ever got a beep as the camera is not focusing for you.
 
You will struggle! Camera shake is magnified along with everything else, so you need even higher shutter speeds, on top of needing high f/numbers to get even a little depth of field. Flash (ring-flash) is the usual answer.

You're not getting focus-confirm because the AF system will have packed up. At a magnification ratio of 1:1, which is about where you'll be, the effective aperture is reduced by two stops, so f/5.6 becomes and effective f/11 which is too far above the f/5.6 AF ceiling to have much chance.

But you don't want AF or focus-confirm. Set manual focus, get everything roughly right by hand and then move your body back and forth very gently to achieve sharpest focus visually in the viewfinder.

It's not easy at the best of times ;)
 
You wont get the focus confirm beep if in manual mode.
 
Hi guys,

Just wanted to reply to the responses:

I definitely do get a confirm bleep even on manual focus as I can hear it when I have none to 2 tubes fitted; it's just when all 3 tubes are fitted i rarely (if ever) get a confirmation & I wondered if anyone knew a reason why of if I could do anything to help?

Thanks for the advice about fixing the focus & moving my body back & forth; I'm doing that but am guessing am not too good at it just yet.

I've also heard that using apertures of above f/8 can give bad cases of defraction making the image appear blurry, and I was wondering if it is possible to tell the difference between bad focus & defraction when looking @ the final image?

Thanks again for any help / advice,

Jay.
 
Ps. HoppyUK,

Thanks again for your input, but what did you mean by the aperture being above the AF 5.6 ceiling?

And you mentioned a ring flash being the answer? I'm guessing that it just allows you to shoot at really fast shutter speeds, as well as having small aperature (high f/number) for max. DOF?
How close are you able to get with a ring flash btw = in some instances I'm prob 20mm from my subject with my lens; would a ring flash still be suitable in that case?

Thanks again for all your help,

I really appreciate it,

Jay.
 
Jayceyned said:
I've also heard that using apertures of above f/8 can give bad cases of defraction making the image appear blurry
Click to expand...

Diffraction will make an image blurrier at narrow apertures, but the effect is often over-emphasised.

Here's a 100% crop from a macro image of a tenner at f/5.6 -

DiffTest%20002.jpg


And here it is at f/22 -

DiffTest%20005.jpg



As you can see, the blur is much worse at f/22 - not!
 
Jayceyned said:
Ps. HoppyUK,

Thanks again for your input, but what did you mean by the aperture being above the AF 5.6 ceiling?

And you mentioned a ring flash being the answer? I'm guessing that it just allows you to shoot at really fast shutter speeds, as well as having small aperature (high f/number) for max. DOF?
How close are you able to get with a ring flash btw = in some instances I'm prob 20mm from my subject with my lens; would a ring flash still be suitable in that case?

Thanks again for all your help,

I really appreciate it,

Jay.
Click to expand...

F/numbers are only true for infinity focus. When you're at 1:1, the f/number changes - laws of physics says it is reduced by two stops, so f/5.6 becomes f/11. In this case though, the camera doesn't know that (it normally switches AF off above f/5.6) so it still tries to AF - or at least the indicator will attempt to show sharpest focus. However, the aperture has just got too small for it to do so, which is why it's normally switched out of course, and while it will usually work, kind of, at f/6.3 or maybe even f/8, at f/11 it has no chance.

Ring-flash gives you plenty of light for high f/numbers, and it's the very fast flash duration of 1/1000sec or usually much less that freezes movement. If you're that close, you really need a longer lens to give you a bit of working distance.

Don't worry about diffraction. If you want ultimate sharpness then don't go above f/16 but in this situation it's likely to be the least of your worries ;) Bear in mind that Frank's shots above are 100% crops.
 
Jayceyned said:
Hi guys,

Just wanted to reply to the responses:

I definitely do get a confirm bleep even on manual focus as I can hear it when I have none to 2 tubes fitted; it's just when all 3 tubes are fitted i rarely (if ever) get a confirmation & I wondered if anyone knew a reason why of if I could do anything to help?

Thanks for the advice about fixing the focus & moving my body back & forth; I'm doing that but am guessing am not too good at it just yet.

I've also heard that using apertures of above f/8 can give bad cases of defraction making the image appear blurry, and I was wondering if it is possible to tell the difference between bad focus & defraction when looking @ the final image?

Thanks again for any help / advice,

Jay.
Click to expand...

I dont get the beep on my camera even without any tubes :)
Do you maybe have the camera on Aperture/Shutter priority but focusing manually or do you have it in M mode?
 
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