is floating element/close range correction on wide-angle lenses worth it?

[darinwc]

Some wide-angle lenses like the olympus 21mm f2 were designed with floating elements.

I thought that by using lenses with such great depth of field, you could get just about everything in focus.
Do you think it is really necessary for wide-angle lenses?

 

[thisismyname09]

I don't think the purpose of floating elements is to get more depth of field, its to correct for other sorts of aberrations that reduce sharpness when you focus up close. When lenses are designed they're, for the most part, designed with focus at infinity in mind. When focusing *really* close, you lose sharpness, not depth of field, because the lens was not designed to perform at such distances. Macro and copy lenses are designed with close focus in mind, and thus don't function well at infinity. Lenses with floating elements are designed to perform well at all distances, so to answer your question, they are necessary if you need the utmost sharpness and work at a wide variety of distances.

 

[AgX]

I thought that by using lenses with such great depth of field, you could get just about everything in focus.

Why do these lenses have a focussing barrel? Even large aperture fish-eye lenses have a focussing barrel.

`In focus´ is a relative term. For best results a lens should be able to be focussed. And then, as said above, one can design additional means to enhance image quality at focus distances off the range which is considered the main range.

 

[Sirius Glass]

Why do these lenses have a focussing barrel? Even large aperture fish-eye lenses have a focussing barrel.

`In focus´ is a relative term. For best results a lens should be able to be focussed. And then, as said above, one can design additional means to enhance image quality at focus distances off the range which is considered the main range.

Use the Zeiss Biogon lenses, like the Hasselblad SWC.

Fish-eye lenses are supposed to have barreling. That is part of the "charm".

Steve

 

[lxdude]

Macro and copy lenses are designed with close focus in mind, and thus don't function well at infinity.

I've always found my macros (EBC Fujinon 55mm f/3.5, Nikkor I.C. 55mm f/3.5, SMC Pentax 100mm f/4, Bronica PE 105mm f/4.5) to work quite well at infinity. Perhaps part of that is the high degree of resolution and correction they have to begin with.

 

[Mike1234]

I removed the floating element from my 55mm Micro Nikkor and dropped it in water. It sank!! So much for truth in advertising...

 

[Q.G.]

You should have dropped the floating element in the water.
Not the 55 mm Mikro Nikkor.

Certainly not when you first remove the floating element from the 55 mm Mikro Nikkor.
What were you thinking ... ?!

 

[keithwms]

Do you think it is really necessary for wide-angle lenses?

Yes, but only if you truly need corner sharpness at a wide aperture.

If your subject is centered and the rest of the frame is outside the depth of field then it won't amount to a hill of beans.

If you stop down extensively (well into the diffraction) then it also will not amount to a['nother, separate] hill of beans.

So, those are two prominent hills of beans that you must steer between if you aim to get the most out of the floating element lenses.

I removed the floating element from my 55mm Micro Nikkor and dropped it in water. It sank!! So much for truth in advertising...

Ha, maybe we need FDA-like disclaimers on the lenses....

 

[AgX]

`In focus´ is a relative term. For best results a lens should be able to be focussed. And then, as said above, one can design additional means to enhance image quality at focus distances off the range which is considered the main range.

I should have added that retro-focus wide-angle lenses are much more prone to reduction of image quality at different focussing distance (typically short distances) than standard wide-angle constructions.

That is why there are no floating elements used in those.

 

[lxdude]

You should have dropped the floating element in the water.
Not the 55 mm Mikro Nikkor.

Certainly not when you first remove the floating element from the 55 mm Mikro Nikkor.
What were you thinking ... ?!

The floating element is actually heavier than water, so you have to place it carefully on the water to make it float.
Out in space, they're all floating elements.

 

[lxdude]

So, those are two prominent hills of beans that you must steer between if you aim to get the most out of the floating element lenses.

I hate it when I get beans in my lenses. Interferes with the floating elements.

 

[lxdude]

Fish-eye lenses are supposed to have barreling. That is part of the "charm".

Steve

 

[lxdude]

You should have dropped the floating element in the water.
Not the 55 mm Mikro Nikkor.

That's elementary.
Maybe he wanted to make it lighter? Of course, painting it white would accomplish that.

 

[Mike1234]

To all who replied to my floating element test: I did drop the floating element in the water... not the lens. As I said before it sank. However, I now realize my mistake. I should have used heavy water.

 

[darinwc]

I removed the floating element from my 55mm Micro Nikkor and dropped it in water. It sank!! So much for truth in advertising...

UUUUUGG! FACE+PALM

 

[lxdude]

To all who replied to my floating element test: I did drop the floating element in the water... not the lens. As I said before it sank. However, I now realize my mistake. I should have used heavy water.

Ah! I now have a nu clear understanding.

 

[Q.G.]

To all who replied to my floating element test: I did drop the floating element in the water... not the lens. As I said before it sank. However, I now realize my mistake. I should have used heavy water.

Ah, yes!
A common, because easy to make, mistake.
Someone should have warned you in advance.

But what did you say before it sank?

 

[darinwc]

Ah, yes!
A common, because easy to make, mistake.
Someone should have warned you in advance.

I think my advance is stuck. It wont move past 24.
And how do I get into play mode?

 

[Q.G.]

And how do I get into play mode?

Press "Play".
Should be near "Pause", and in between "Fast forward" and "Rewind".
Don't touch "Rec" though.

 

[Mike1234]

But what did you say before it sank?

I chanted (not said), "Abbra cadabra... FLOAT, you magical bit of optical wonder"!! Maybe I didn't use the correct chant?!

 

[Q.G.]

I chanted (not said), "Abbra cadabra... FLOAT, you magical bit of optical wonder"!! Maybe I didn't use the correct chant?!

Maybe... yes...
But i still suspect your previous hunch (the non-obese water one) is nearer the mark.

Or... maybe it wasn't a floating element (it didn't, right?), but a flouting element?
What that would entail exactly, i don't know. Yet. But how about it?

 

[Someonenameddavid]

I chanted (not said), "Abbra cadabra... FLOAT, you magical bit of optical wonder"!! Maybe I didn't use the correct chant?!

You should have gone OM




D)

 

[lxdude]

You should have gone OM




D)

With a Nikkor?

 

[Mike1234]

^^^^ I think he meant o-o-h-h-m-m-m-m-m.......... o-o-h-h-m-m-m-m-m.......... o-o-h-h-m-m-m-m-m.......... o-o-h-h-m-m-m-m-m..........

Then again, he was probably making a pun.

 

[David A. Goldfarb]

I should have added that retro-focus wide-angle lenses are much more prone to reduction of image quality at different focussing distance (typically short distances) than standard wide-angle constructions.

That is why there are no floating elements used in those.

Ahem....getting back to the original topic, I agree with this. Wide lenses on SLRs are already at a disadvantage, so anything to improve them is a good thing. Another fault of wide retrofocus lenses at close subject distances can be significant barrel/pincushion distortion, even if they are close to perfectly rectilinear at, say 6 feet or infinity.