Focusing floating element/internal focus lenses on view cameras

[cornwallis]

Hi everyone, first post here on a very informative site!

I'm not sure if this should go here or in the Sony section, but I think it applies equally to digital backs and mirrorless cameras.

For those using view cameras with the above, how do you approach focusing lenses with floating elements/internal focusing? The advice I have received is to set the lens to infinity, and do all the focusing on the rail. This doesn't make sense to me however,
as surely if a lens is engineered to correct/improve performance at different focal distances then the lens itself should be focused appropriately?

In my tests (with a Cambo Actus and Canon 24mm TSE) I have found that on shots focused at around 5m, I get better results in the corners if I first set the lens to approx. 5m, then fine tune with the rail (especially on shifts). I haven't tested any closer as I don't do
that kind of photography, but I would expect the results to be even more pronounced. However... now I have acquired a Canon 16-35mm f4 and found it's better just left at infinity! So I'm a bit confused. I will test some more but I would be interested to hear how other people approach it.

(As expected, when using a lens that moves the whole lens group together (in this case a Pentax 645 35mm) it makes no difference where the lens barrel is focused, except that at infinity there's a little less vignetting at the very edge of the IC.)

Matthew

 

[foveon]

what i remember from my RB 67 50mm lense the floating element is only used for close ups, the other time set to infinity^^

 

[neil]

I am using an adapted RZ macro lens on a view camera.

I find that it's a major benefit to have a floating element group. This allows me to get sharper corners at wider open f numbers.

My workflow is simple.

Either set at infinity or take a guess at where to set the floating element.
Focus
Take a shot and check corners
Adjust floating point and iterate

Quite surprising how much difference it can make to corner sharpness.

Alternative is to stop down and then it's not necessary to adjust the floating element. But the downside is diffraction kicks in.

For optimal sharpness I open up the lens as much as possible and use the floating elements to sharpen the corners.

In summary I think of the floating element as having an additional way to sharpen the corners. If the corners are already sharp it's not necessary to use. But if the corners are fuzzy then the floating element gives you a way to try and sharpen them. Might be simplistic way but seems to yield good results. It makes the biggest difference on close up items but also helps with items a few meters away. Especially flat field copy work.

 

[TimoK]

If you think lens designer at work, I believe he must have good reasons to use so mechanical ( and maybe optical) complicated construction as floating element(s).
It makes lens heavier and more expensive. So, advantages in image quality have to be remarkable to pay those disadvantages.
I use one fle lens with Cambo Actus, Hbl Distagon 50mm Cf FLE. I first set the focussing ring to infinity point and then focus to some distant target using the rail. That's the starting point. Then I set the fle ring according shooting distance and focus with lens' focussing ring. I have not made any test if I should do some other way, but I think I'm getting pictures good enough (if looking sharpnes only).
Btw. my 24 tse II focuses over infinity. I made my own infinity mark with tape by focussing into full moon. It's quite near to the imagined 5m setting.

 

[GrahamWelland]

Btw. my 24 tse II focuses over infinity. I made my own infinity mark with tape by focussing into full moon. It's quite near to the imagined 5m setting.

No surprise about focus beyond infinity with a TSE lens - you need to be able to do this when you tilt.