# Using extension tube with zoom lens for closeup

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#### Celsius

##### New Member
I have seen some of you guys use a zoom lens lik 70-200mm lens with a 25mm extension tube for macro work. However I read somewhere that such combi can reach only reach a magnification of 1/8X at 200mm. How is it possible for you guys to have such good magnification? Please enlighten. Thanks.

#### xdivider

##### New Member
Celsius said:
I have seen some of you guys use a zoom lens lik 70-200mm lens with a 25mm extension tube for macro work. However I read somewhere that such combi can reach only reach a magnification of 1/8X at 200mm. How is it possible for you guys to have such good magnification? Please enlighten. Thanks.
where did u get the 1/8 figure from? By right at standard focussing distance of 1.5m, a 200mm lense should achieve 200/1500 = 1/7.5 without anything.

#### Celsius

##### New Member
xdivider said:
where did u get the 1/8 figure from? By right at standard focussing distance of 1.5m, a 200mm lense should achieve 200/1500 = 1/7.5 without anything.
Magnification = extension tube length / focal length ?
Or did I get the formula wrong?

#### xdivider

##### New Member
Celsius said:
Magnification = extension tube length / focal length ?
Or did I get the formula wrong?
I think u have to take into consideration the minimum focussing distance of a lens. The lens has a built-in extension.

If i dun get wrong
Total extension = tube length + lens extension
Magnification = Total extension / Focal length of lens

Assuming the lens has ard 25mm extension by itself, this gives u total 50mm with a tube and ard 50/200 = 1/4 X.

Correct me if im wrong abt this.

#### Celsius

##### New Member
You might be right. Still 1/4x seems quite far from life size magnifcation. But judging from some of the closeup/macro shots posted here with such a setup seems quite near 1:1 magnification.

xdivider said:
I think u have to take into consideration the minimum focussing distance of a lens. The lens has a built-in extension.

If i dun get wrong
Total extension = tube length + lens extension
Magnification = Total extension / Focal length of lens

Assuming the lens has ard 25mm extension by itself, this gives u total 50mm with a tube and ard 50/200 = 1/4 X.

Correct me if im wrong abt this.

#### xdivider

##### New Member
Celsius said:
You might be right. Still 1/4x seems quite far from life size magnifcation. But judging from some of the closeup/macro shots posted here with such a setup seems quite near 1:1 magnification.
Adding in the crop factor for dslrs, this reaches a respectable 1/3X which is pretty reasonable for large insects like butterflies. Also, some lenses may have close foccusing modes which may affect the calculations.

#### Sgt. Pepper

##### New Member
Celsius said:
I have seen some of you guys use a zoom lens lik 70-200mm lens with a 25mm extension tube for macro work. However I read somewhere that such combi can reach only reach a magnification of 1/8X at 200mm. How is it possible for you guys to have such good magnification? Please enlighten. Thanks.
Hi Celsius,
I assume you&#8217;re referring to my Thread .

The magnification you gain from Extension tube is dependent on both focal length and extension tube length. For subject below 20cm size, I normally stays at 70mm-100mm focal length, unless I want more working distance then I&#8217;ll use 150mm-200mm of course magnification will be lesser.

Like what xdivider said, crop factor of 1.6X for DLSR plays an important role to increase the magnification as well. But, I always based my calculation using the standard formula we all know. (ExTube length / focal length)

For my above thread, it was shot at around 100mm, 150mm and 75mm repectively (with 10-20% cropping)

One of the best way to increase magnification is to use an Extender between the cam and the extension tube. In this matter, the extender will multiply your extension tube strength leaving the minimum focusing distance the same.

This was shot using 70-200mm + 25mm ext tube + 1.4X TC at 70mm focal length. (cropped about 5% only) Your 25mm now becomes 35mm giving you around 1/2X at 70mm focal length.

#### Kelvin^Newbie

##### New Member
Sgt. Pepper said:
Hi Celsius,
I assume youre referring to my Thread .

The magnification you gain from Extension tube is dependent on both focal length and extension tube length. For subject below 20cm size, I normally stays at 70mm-100mm focal length, unless I want more working distance then Ill use 150mm-200mm of course magnification will be lesser.

Like what xdivider said, crop factor of 1.6X for DLSR plays an important role to increase the magnification as well. But, I always based my calculation using the standard formula we all know. (ExTube length / focal length)

For my above thread, it was shot at around 100mm, 150mm and 75mm repectively (with 10-20% cropping)

One of the best way to increase magnification is to use an Extender between the cam and the extension tube. In this matter, the extender will multiply your extension tube strength leaving the minimum focusing distance the same.

This was shot using 70-200mm + 25mm ext tube + 1.4X TC at 70mm focal length. (cropped about 5% only) Your 25mm now becomes 35mm giving you around 1/2X at 70mm focal length.

newbie for this thing

70-200mm + 25mm ext tube + 1.4X TC

how close can i get to?

#### Sgt. Pepper

##### New Member
Kelvin^Newbie said:
newbie for this thing

70-200mm + 25mm ext tube + 1.4X TC

how close can i get to?
@70mm + 25mm ext tube, the min focusing distance is about 4-5 inches. If you add 1.4X TC, the min focusing distance should not change but the magnification will be higher by 1.4 times.

#### Kelvin^Newbie

##### New Member
Sgt. Pepper said:
@70mm + 25mm ext tube, the min focusing distance is about 4-5 inches. If you add 1.4X TC, the min focusing distance should not change but the magnification will be higher by 1.4 times.
i seem so blur :bsmilie: wanted to buy and try it out ... how much is 25mm ext tube and 1.4X TC . . .

#### Sgt. Pepper

##### New Member
Kelvin^Newbie said:
i seem so blur :bsmilie: wanted to buy and try it out ... how much is 25mm ext tube and 1.4X TC . . .
Kenko extension tube set is going for 280\$ +/- (not very sure how much now, but around that price). It comes with 3 sizes: 12mm, 25mm and 36mm.

Uniplus 25mm is around 90\$ at CP.

1.4X Kenko pro300 is around 320\$ @TCW.

you may call them and check the latest price:
CP: 63374274
TCW: 63361956

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