[jfuqua11]

I am hoping someone can help me with my question about the Pentax D FA 100mm f/2.8 WR. I am thinking about getting a bellow or some extension tubes, but I am wondering what is the maximum magnification I can achieve with this lens. I know it is a 1:1 with a minimum focus is about 5 inches from the front element. So I am wondering if anyone knows, by trial or anyone smart enough to calculate it out, using extension tubes or a bellow what is the maximum magnification ratio that this lens can achieve before your front element is touching the subject.

Thank you,

James

[jatrax]

Just FYI but that lens has no aperture ring so it will always shoot wide open, not ideal for macro.

Here is a thread with some good info: https://www.pentaxforums.com/forums/58-pentax-beginners-corner-q/110579-lense...ification.html

If you want to do bellows, get an M42 bellows, k-->M42 adapter and either a 100mm bellows lens or an m42 100mm macro. You could do it all k-mount as well but I think you will have less money in an m42 rig.

[elliott]

You'd need a lot of extension to focus really close to the front element. I have the equivalent of a 100mm 1:1 macro and tried it on 75mm of extension tubes and was still a little over 3" from the front element. I think the magnification at this point was 1.75:1, to get 2:1 you'd need 100mm of extension tubes.

[jfuqua11]

You'd need a lot of extension to focus really close to the front element. I have the equivalent of a 100mm 1:1 macro and tried it on 75mm of extension tubes and was still a little over 3" from the front element. I think the magnification at this point was 1.75:1, to get 2:1 you'd need 100mm of extension tubes.

Okay good!! That makes sense, double the length and double the magnification. I was worried that I would run out of room, in this case I will go with a bellow 40mm - 150mm extention! so I should be able to get a 2:1 Thank you for your help Elliot!

[sterretje]

If you want to do bellows, get an M42 bellows, k-->M42 adapter and either a 100mm bellows lens or an m42 100mm macro. You could do it all k-mount as well but I think you will have less money in an m42 rig.

I'm still trying to find a way to fit my M42 bellows on my Pentax dSLR and afterwards be able to get it off . The protruding flash is in the way so you can't unscrew it. This means that you need either an additional extension tube or an adapter 'glued' to the bellows

Not wanting to hijack the thread, but any thoughts on that (for me and the OP)?

[jatrax]

I'm still trying to find a way to fit my M42 bellows on my Pentax dSLR and afterwards be able to get it off .

I have the Pentax Bellows II (PENTAX Bellows Unit II (M42) reviews - Pentax Camera Accessory Review Database) and it has a lock screw on the camera end that holds a male M42 threaded metal piece. I attached a flanged M42-->K-mount adapter to the M42 thread and just lock the adapter onto the camera. Then the bellows just slides on and is secured by the locking screw. You do not have to unscrew the bellows. Not sure how others are made but no issues with mine.

[Just1MoreDave]

Okay good!! That makes sense, double the length and double the magnification. I was worried that I would run out of room, in this case I will go with a bellow 40mm - 150mm extention! so I should be able to get a 2:1 Thank you for your help Elliot!

Like jatrax said in the first reply, the WR 100mm macro has no aperture ring. It works best with a full set of electrical and mechanical connections between lens and camera. The Pentax-A bellows might work. Otherwise the lens will probably shoot fully stopped down. You can maybe wedge the aperture lever in an intermediate position, but it will be difficult to change apertures. Focus will be harder too.

[Just1MoreDave]

I'm still trying to find a way to fit my M42 bellows on my Pentax dSLR and afterwards be able to get it off . The protruding flash is in the way so you can't unscrew it. This means that you need either an additional extension tube or an adapter 'glued' to the bellows

Not wanting to hijack the thread, but any thoughts on that (for me and the OP)?

The flanged adapters are a good idea. The extra thickness of the flange just adds a bit to the bellows length. You could permanently attach the flanged M42 to K adapter to an M42 extension tube or TC with optics removed. That would poke out enough to clear the flash housing. Then you could keep the bellows unmodified.

[baro-nite]

The Pentax-A bellows might work. Otherwise the lens will probably shoot fully stopped down.

The Pentax Bellows-A does not have the A contacts. The lens would always be wide open because the bellows does have a diaphragm actuator (operated by a cable release). Only if you mounted the lens on a non-auto tube would it be stopped down.

Back to the original question, what magnification would you like to achieve? A shorter-FL lens mounted in reverse is a relatively cheap and easy way to get extreme magnification, if that's what you're after.

[jfuqua11]

Well, I already have the 100mm WR lens. Maybe I can use some tape of something to lock the actuator arm in the middle which would give me about f16 (what I normally shoot anyway). The other option was to buy a new (old) lens for use with the bellows, probably the Sigma 105mm.

[bassek]

Well, I already have the 100mm WR lens. Maybe I can use some tape of something to lock the actuator arm in the middle which would give me about f16 (what I normally shoot anyway). The other option was to buy a new (old) lens for use with the bellows, probably the Sigma 105mm.

...or the M100/4.

Seb

[elliott]

...or the M100/4.

Seb

That one is only capable of 1:2 on its own, so even more extension would be needed to reach 2:1.

[baro-nite]

Well, I already have the 100mm WR lens. Maybe I can use some tape of something to lock the actuator arm in the middle which would give me about f16 (what I normally shoot anyway). The other option was to buy a new (old) lens for use with the bellows, probably the Sigma 105mm.

There are other ways of increasing magnification that would allow better control of the aperture setting and better handling. Consider a Raynox or a 2x TC. For 2x on a bellows try a reversed 50mm lens. The M50/1.7 is cheap and works pretty well for this. An EL-Nikkor 50/2.8 is a bit better still and about as cheap. My favorite lens for reversing is the SMC Pentax 1:3.5 28mm (i.e., the K28/3.5), also an excellent lens all around.

[bassek]

That one is only capable of 1:2 on its own, so even more extension would be needed to reach 2:1.

You are quite right, I forgot that it's 1:2...

Reversing almost any 28/35/50 on a bellows might be the best and most economical solution.

Seb

[jeffshaddix]

As for the extension tube/bellows discussion, don't forget tubes with A contacts do exist. I have a vivitar set that works great. I also happen to have the 100 WR, so I'll test that out for you and report back.