Extension Tube question

hark

hark

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I still have a lens that I used with my N90s. It is a Sigma AF 70-210mm f/3.5-4.5 APO macro. Granted it is not a true macro lens--I'm not sure if it is 1:2 or 1:3, but will extension tubes work with this type of zoom macro lens? As a telephoto lens, it was pretty sharp--even sharper than the Sigma 28-70mm f/2.8 I used back then. I've kept it because of its low light ability and used it for taking photos of the local high school students theater productions prior to getting a new Sigma 70-200mm f/2.8. Since I've never used extension tubes, I don't know if compatibility is even an issue since the tubes don't have any glass....:eek:

​Thanks for any help! :)
 
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Bill16

Senior Member
I've used my extension tube with my 105mm micro and my 200mm ai lenses and have had no issues. But I haven't used it on a zoom lens. I would think it would work, but I don't think the zoom feature will be very useful. I just can't say for sure. Sorry.
 
Fred Kingston

Fred Kingston

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It would work... fundamentally, all an extension tube does is move the focus point out away from the focal plane of the film/sensor...

​You'd manually focus of course, but the metering system should work because it's just measuring the light that enters the lens... If you delve into the Nikon extension tube charts, you'll find a chart that lists the compatible extension tube series with your version/vintage of lens...
 
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WayneF

Senior Member
FredKingston said:
It would work... fundamentally, all an extension tube does is move the focus point out away from the focal plane of the film/sensor...

​You'd manually focus of course
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Technically, when the focus is moved way out, the lens no longer can focus - at least the focus ring is not designed for this new extreme range. Which is true of all lenses, and the way we have to focus with extension tubes is by moving the camera back and forth, to find the one place where it actually achieves focus.

Just saying, first appearance is that it cannot focus, but the workaround is to do it by moving the camera back and forth. This is difficult on a tripod. You can buy focusing rails to help do this, but the cheap and easy way is to place the macro subject on a small board, and slide the board back and forth in front of camera.
 
hark

hark

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Bill16 said:
I've used my extension tube with my 105mm micro and my 200mm ai lenses and have had no issues. But I haven't used it on a zoom lens. I would think it would work, but I don't think the zoom feature will be very useful. I just can't say for sure. Sorry.
Click to expand...

This is the only macro type lens I've ever used. I have to zoom all the way out to 210mm then flip a switch which locks the zoom. Otherwise it won't go into macro. It won't do macro at any other zoom length. I have no clue as to how any other macros work. :)

FredKingston said:
It would work... fundamentally, all an extension tube does is move the focus point out away from the focal plane of the film/sensor...

​You'd manually focus of course, but the metering system should work because it's just measuring the light that enters the lens... If you delve into the Nikon extension tube charts, you'll find a chart that lists the compatible extension tube series with your version/vintage of lens...
Click to expand...

It's a Sigma lens, but maybe I can contact someone at Sigma to find out. When I ran into a problem with my Sigma Circular Polarizer this summer, the customer service rep said not to hesitate asking her any questions. I just might ask! ;)

WayneF said:
Technically, when the focus is moved way out, the lens no longer can focus - at least the focus ring is not designed for this new extreme range. Which is true of all lenses, and the way we have to focus with extension tubes is by moving the camera back and forth, to find the one place where it actually achieves focus.

Just saying, first appearance is that it cannot focus, but the workaround is to do it by moving the camera back and forth. This is difficult on a tripod. You can buy focusing rails to help do this, but the cheap and easy way is to place the macro subject on a small board, and slide the board back and forth in front of camera.
Click to expand...

This lens doesn't have any VR so I always use a tripod--yes, I am familiar with moving the tripod/camera/lens back and forth to achieve focus. So the AF won't work with extension tubes then? I know it is better to use Manual Focus for macro, but sometimes it is easier to at least get close to achieving focus by using the Auto Focus.

Thanks for all the info! :D

So if I am at 1:3 macro while using extension tubes, does anyone have any idea what the ratio becomes? I'm looking at the Kenko extension tubes.
 
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480sparky

Senior Member
hark said:
..............So if I am at 1:3 macro while using extension tubes, does anyone have any idea what the ratio becomes? .........http://www.bhphotovideo.com/c/product/375238-REG/Kenko_AEXTUBEDGN_Auto_Extension_Tube_Set.html.
Click to expand...

I'm gonna go out on a limb here and say............... One to three.
fiufiu.gif
 
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WhiteLight

Senior Member
Kenko extension tubes would allow you to focus through the camera...
Have them & use it with my 105mm 2.8g

Regarding the ratio, adding all 3 extension tubes at 1:1 focus would give you 1:16 times the magnification.
Now don't ask me the math :D
 
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480sparky

Senior Member
WhiteLight said:
Kenko extension tubes would allow you to focus through the camera...
Have them & use it with my 105mm 2.8g

Regarding the ratio, adding all 3 extension tubes at 1:1 focus would give you 1:16 times the magnification.
Now don't ask me the math :D
Click to expand...

Adding extension tubes to a lens with a native 1:1 ratio shouldn't reduce it to 1:16. It should increase it, to something like 2:1.
 
hark

hark

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Okay, at least I know it will increase the magnification--if it starts out as 1:3, then should the extension tubes increase it to at least 1:1? And if so, how would an image taken with a lens/extension tubes compare with a genuine macro lens that has 1:1 built in? Any degradation? I know the light will be cut down, but does the image quality suffer when extension tubes are added?
 
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480sparky

Senior Member
hark said:
Okay, at least I know it will increase the magnification--if it starts out as 1:3, then should the extension tubes increase it to at least 1:1? And if so, how would an image taken with a lens/extension tubes compare with a genuine macro lens that has 1:1 built in? Any degradation? I know the light will be cut down, but does the image quality suffer when extension tubes are added?
Click to expand...

The only way to know what ratio you have is to measure it. I shoot a ruler marked in 1/32" and compare the result to the sensor size.

As for image degradation, there isn't much.... DOF becomes the real issue. Once you really start to get into high magnifications, you might get into vignetting issues, as well as magnifying the minor defects in the lens.
 
hark

hark

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480sparky said:
The only way to know what ratio you have is to measure it. I shoot a ruler marked in 1/32" and compare the result to the sensor size.

As for image degradation, there isn't much.... DOF becomes the real issue. Once you really start to get into high magnifications, you might get into vignetting issues, as well as magnifying the minor defects in the lens.
Click to expand...

Ah! Got it! Thanks! ;)
 
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WhiteLight

Senior Member
480sparky said:
16:1 is a lot to ask of extension tubes, even on a 1:1 macro lens.
Click to expand...

I could be wrong, but i remember reading it somewhere..
This is the actual formula for calculating Magnification Ratios :D

Mag. Ratio = ((Length of Ex. Tube)+ (Master Lens Advance Volume Image)) / Master Lens Focus Length

Where Master Length Advance Volume = ((Master Lens Focal Length)^2)/(Master Lens Distance Reading - Master lens focal length)

:encouragement:
 
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emm2600

Senior Member
Bill16 said:
I've used my extension tube with my 105mm micro and my 200mm ai lenses and have had no issues. But I haven't used it on a zoom lens. I would think it would work, but I don't think the zoom feature will be very useful. I just can't say for sure. Sorry.
Click to expand...

If it's not an internal focus/internal zoom type lens (i don't think the OP's sigma is) then using the lens with tubes can get a little more complicated. You are right about the zoom feature being not that useful - i've used an older tamron non-internal d-type zoom with tubes and it basically turned the zoom ring into a focus fine-tune ring. More from just moving the position of the front element than anything i'm guessing.
 
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