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Extension Tubes

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Just Jas
Just Jas  1225748 forum posts England1 Constructive Critique Points
16 Jul 2004 - 8:21 AM

Zubes is good for your tubes! Smile)

jas

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16 Jul 2004 - 8:21 AM

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nikon5700ite
16 Jul 2004 - 8:36 AM

Extension tubes move the centre [diaphragm ] of the lens forward and you are working with a longer focal length lens so the effective aperture is reduced... but with TTL metering the camera sorts all this out for you unlike the poor studio cameraman with his 5x4 camera [etc] who has to do the calculations .... one of the reasons I loved my first Pentax with it's metering through the lens ... no matter what I did, which included holding the lens a few inches in front of the camera with a drainpipe connection for big macro*, the camera gave me the correct exposure.

*filling the 35mm frame with part of a 16mm film frame.

theorderingone
17 Jul 2004 - 11:56 PM

That's true with centre weighted, or any other non-evaluative metering system as this only works out the exposure from the light entering the lens. Matrix and evaluative systems use the max apeture info to calculate how bright the light is BEFORE it has entered the lens as it knows how much light is impeded by the lens. If you alter this by putting tubes or a teleconverter on the lens, this leads to incorrect exposure using those metering systems. If the camera thinks you are using an F4 lens and you lose two stops to the tubes, then the camera will presume that the subject is only 1/4 as bright as it is and calculate the exposure accordingly.

timtom1
timtom1  1026 forum posts
2 Aug 2004 - 7:17 PM

Disaster! The photos I took with my extension tubes I took have not come out. I put my camera onto manual focus and the shutter and aperture to just picture so I was letting the camera work that part out.

francisg
francisg  10703 forum posts United Kingdom1 Constructive Critique Points
2 Aug 2004 - 9:27 PM

In what way did they fail?

theorderingone
3 Aug 2004 - 12:05 AM

Over/under-exposed? Out of focus?
A bit more info will help us to help you.

timtom1
timtom1  1026 forum posts
3 Aug 2004 - 8:10 AM

Hi again;

I just got back a long black strip of film of about 8 photos long, where I had tried to use the extension tubes for those photos. All the other photos turned out fine, where the tubes were not used.

I meant to say that the focus was on manual and the shutter speed and apature were on manual as well not just the pictureoption;
They are Jessops auto extension tubes and I put the set of three on which were 13mm, 21mm and 31mm and I am using a Nikon F80 and the film was Provia F100.

keithh
keithh  1022812 forum posts Wallis and Futuna29 Constructive Critique Points
3 Aug 2004 - 8:17 AM

First off, using all those tubes makes the focusing plane extremely narrow. You would be better off when starting to use a faster film and choose aperture priority, you'll know from the cameras chosen shutter speed if you're going to be able hand hold or need to use a tripod or some other stabiliser.
You would be better starting with one tube and working your way up.

timtom1
timtom1  1026 forum posts
3 Aug 2004 - 9:12 AM

What would be the best aperture, when using the 31mm with a 70 x 300mm Nikkor lens?

brm
brm  1076 forum posts
3 Aug 2004 - 9:23 AM

The best aperture for what? As keith said the focusing plane is going to be v. narrow indeed with extensions tubes. You will definately need a tripod with a 31 mm ext. tube and if you've got a tripod you can use whatever aperture you want, personally I've never managed to get a good handheld shot with anything greater than a 12 mm tube.

b

keithh
keithh  1022812 forum posts Wallis and Futuna29 Constructive Critique Points
3 Aug 2004 - 9:26 AM

Aperture would depend on your subject, but remember to think in a macro world. You can't look at the shot from a 'normal' viewpoint, everything within it is compounded.

theorderingone
3 Aug 2004 - 3:52 PM

If your using an F80 with the Jessops tubes you have no way to meter as those tubes are meant for NIkon NAI (Manual focus cameras like the FM2 or the FG20).
Try using print film, the extra exposure latitude could mean you end up with something vaguely usable, or (and I would strongly recommend this!) take the tubes back to Jessops and demand a full refund! Ask them why they sold you manual tubes for an AF camera, (they should know they don't work!). Then save another 50 and get a set of teleplus AF extensions tubes, then you will be able to use your cameras meter.

Hope I'm barking up the right tree and that it is of some use!

timtom1
timtom1  1026 forum posts
3 Aug 2004 - 3:56 PM

Ahh problem, I ordered them from Jessops online shop, and I can;t find my receipt! This is what I ordered
www.jessops.com/search/viewproduct.cfm?PRODUCT=JESAETNAI&BRAND=&CONTINUE...

timtom1
timtom1  1026 forum posts
3 Aug 2004 - 4:29 PM

Took your advice theorderingone found my receipt and they are going back tomorrow.

theorderingone
3 Aug 2004 - 9:59 PM

Make sure you give 'em a good earbashing from me!

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