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05-15-2010, 11:07 PM   #1
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How to achieve 5:1 magnification ?

Hi guys, to my knowledge the only macro lens that can do this is the Canon MP-e65.
However, I'm not willing to buy a Canon body (plus flash) just to accommodate those lens. I'd like to fill my 24" screen with a bug's eye though. How can I achieve 5:1 magnification (and more) on my K20D and keep a good distance from the subject at the same time? Will a fully stretched bellows plus a 70mm 1:1 Sigma macro give me that? Or do I have to use a smaller focal length 1:1 macro lens such as a 35mm Pentax limited? Thanks.

05-15-2010, 11:20 PM   #2
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A Pentax 28mm lens (example: K28/3.5, M28/2, M28/2.8 & M28/3.5) reversed on a fully extended (140mm) Bellows, will give you around 6.8:1 magnification. You sould be able to buy a manual Bellows and a K or M28/3.5 for a couple hundred dollars, which is a lot less than the
Canon MP-e65.

Phil.
05-15-2010, 11:24 PM   #3
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Thanks, Phil,

and if I prefer not to reverse lens?
05-15-2010, 11:35 PM   #4
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Maybe a little over 1:1, like 1.2:1. Reversing is the key.

Phil.

05-15-2010, 11:42 PM   #5
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Phil, what I meant to do is

put a 1:1 MACRO lens at the end of a 140mm bellows.
The lens without the bellows is already capable of 1:1....
How can I only get up to 1.2:1 with the addition of the bellows?
Am I missing the boat completely?
Thanks for your time.
05-15-2010, 11:45 PM - 1 Like   #6
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According to these tables (for reversed lenses):



You can get 5:1 if you add 160mm extension tube to a 35mm lens reversed, or 130mm to a 28mm lens reversed.

Note that whatever you're photographing will be very close to the rear of the lens (now in front). For example, if you add 130mm extension tube to a 28mm lens, the distance from the object to the sensor plane has to be 227mm. Let's say the lens is about 30mm long. From the rear of the lens to the object will be about 60mm, about 2.5 inches.

With the exposure factor about 30X, you definitely need a flash.

Another way is to use a reverse adapter. I don't know the formula. But I think a 135mm + a reversed 28mm will give you the magnification in the ball park.
05-15-2010, 11:50 PM   #7
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Thanks !

These 35mm and 28mm lens on top of the charts - are they MACRO lens, or regular primes? If they are regular lens, then I have a further question:

What happens to these numbers when a 1:1 macro lens (of same focal length) is mounted at the end of the bellows versus regular lens?

Thanks.
05-15-2010, 11:55 PM   #8
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QuoteOriginally posted by mrpink Quote
These 35mm and 28mm lens on top of the charts - are they MACRO lens, or regular primes? If they are regular lens, then I have a further question:

What happens to these numbers when a 1:1 macro lens (of same focal length) is mounted at the end of the bellows versus regular lens?
They are "regular" lenses in reverse.

A macro lens at 1:1 is essentially a "regular" lens + an extension tube as long as the focal length of the lens.

So for a macro lens of 100mm focal length that can do 1:1 by itself, if you add 100mm worth of extension tube, you'll have 2:1.

05-16-2010, 12:01 AM   #9
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Thanks. And shall I assume that

by using a 50mm 1:1 macro with 100mm extension I'd get 4:1 ?
05-16-2010, 04:31 AM   #10
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100mm with a regular 50mm focused at infinity will give you 2:1

100mm with a 50mm at 1:1 will give you 3:1

A 50mm at 1:1 has already 50mm extension so a 50mm at 1:1 plus 100mm extension , is basically a 50mm focus at infinity plus 150mm of extension . 150 / 50 = 3
05-16-2010, 07:48 AM   #11
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Thanks Mer

for also giving me the format to calculate it for myself.
So by this format it seems that a longer focal length macro lens (which although would give me a better working distance), would actually be a disadvantage for the magnification ratio.... fascinating.

So let's see then: using a 35mm 1:1 macro lens at the end of a 175mm extension is what will give me a 5:1 magnification then if I'm not mistaken. Almost no light in the barrel though, and the glass probably a few milimeters from the subject.

Am I correct, guys? If yes, my next question is:

Won't these numbers be affected by the K20D sensor's crop-factor?

thanks!
05-16-2010, 08:58 AM   #12
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bellows and smc macro 50 f4

I use Asahi Pentax Autobellows. I have the manual and it states that if you can get the smc macro takumar 50 1.4 lens and the autobellows you can achieve 4.3. You can get up to 4.88 if you add tubes to the bellows.

I use enlarging lenses and with a 50mm lens - with bellows fully extended (170mm) I see 7mm from frame to frame. I think on 35mm film this would be about 5:1. I have no idea how crop factor impacts this. On my camera the crop factor is 1.6

The lens / bellows cost about $100. If interested you can read about enlarging lenses for macro at the link in my signature below.

05-16-2010, 09:28 AM   #13
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Remember that when you get beyond 1:1, light becomes more of a critical issue and the greater the mag, the trickier the dof becomes for focusing. That is why a focus rail is needed and why bellows of an integrated focusing rail.

Also look at the possibility of stacking lenses if you don't like the idea of a reversed lens. You could reverse a 28mm on a AF 105mm and get at least 3.75x and maintain your A contacts.
05-16-2010, 11:09 AM   #14
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Also, you mention in your original post that you want a "good distance to subject". Any of these methods that give you 5:1 magnification with only a 50-100mm as your basic focal length will have working distances measured in fractions of an inch. the only way to longer working distances in macro photography is to start with much higher focal lengths. Is there a particular application you have in mind here? It occurs to me that you might really need to be looking at completely different solutions, such as shooting lower magnification from a greater distance and then cropping.
05-16-2010, 03:20 PM   #15
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Thanks Marc,

Maybe I outta get a Canon body just to accommodate the mp-e65 lens. I didn't wanna do it because I much prefer the K20D to almost anything Canon, (maybe short of the 5DmkII).

I know there is no Canon glass to Pentax K adapter, but there is Canon to Leica and then Leica to Pentax (just an example).

Can one piggyback two adapters to adopt a lens to a body ???

Thanks!
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