Ideal Working Aperature Range Rodenstock lens

[David Solow]

Hi All,

I have a few Rodenstock lenses. Rodenstock lists ideal working apertures for their lenses. What does that mean exactly? For instance, the 75mm f/4.5 has an ideal working range from f/16 to f/22. Does that mean there is vignetting with apertures larger than f/16 or diffraction with apertures smaller than f/22?

Thanks,

David

[Bob Salomon]

diffraction

[David Solow]

Thanks, Bob.
I'm not sure that I understand completely. Why the range then? If it's diffraction, why not just say that diffraction will be a factor with apertures smaller than f/22? The 210mm has a range of f/16 to f/32. Does diffraction become a factor in some situations with apertures smaller than f/16 but in other situations with apertures smaller than f/32?

David

[E. von Hoegh]

It depends on how much you are going to enlarge the negative. A 210 is a 5x7 lens, although it can be used on any format it will cover.

[David Casillas]

I believe that according to Rodenstock literature, the smaller aperture of the published aperture range should be used when camera movements are applied.

[Oren Grad]

Rodenstock lists ideal working apertures for their lenses. What does that mean exactly?

Not much. It's a rule of thumb for the range in which you'd get the best bench-test results while still being practical for many real-world subjects. At wider apertures aberrations are not so well controlled, while at smaller apertures diffraction takes an ever larger toll.

I often use my Rodenstock and other brand lenses outside of those ranges.

[E. von Hoegh]

Not much. It's a rule of thumb for the range in which you'd get the best bench-test results while still being practical for many real-world subjects. At wider apertures aberrations are not so well controlled, while at smaller apertures diffraction takes an ever larger toll.

I often use my Rodenstock and other brand lenses outside of those ranges.

Exactly, it's a guide/reccomendation.

[Bob Salomon]

Exactly, it's a guide/reccomendation.

No it is the point at which diffraction will start to degrade the image on the format that the lens was primarily designed for.
What Rodenstock says is:

"A certain amount of stopping down is also normally required to suppress the residual aberration that can never be corrected to 100%. But at low (small) apertures diffraction increases - an unadvoidable physical effect - so that sharpness is visibly reguced. For this reason you should never stop down any more than absolutely necessary.

Under optimum circumstances lenses for the most popular large format 4x5" should be stopped down to f22; smaller apertures may be necessary and permissible as well with larger formats (see chart below which you can see if you download the brochure). If a great deal od depth of field is required, the aperture can be stopped down by one more stop without any substantial loss in sharpness. Rollfilm formats typically need working apertures around 8 to 16."

[E. von Hoegh]

No it is the point at which diffraction will start to degrade the image on the format that the lens was primarily designed for.
What Rodenstock says is:

"A certain amount of stopping down is also normally required to suppress the residual aberration that can never be corrected to 100%. But at low (small) apertures diffraction increases - an unadvoidable physical effect - so that sharpness is visibly reguced. For this reason you should never stop down any more than absolutely necessary.

Under optimum circumstances lenses for the most popular large format 4x5" should be stopped down to f22; smaller apertures may be necessary and permissible as well with larger formats (see chart below which you can see if you download the brochure). If a great deal od depth of field is required, the aperture can be stopped down by one more stop without any substantial loss in sharpness. Rollfilm formats typically need working apertures around 8 to 16."

Exactly, it's a guide/reccomendation.

[Bob Salomon]

Exactly, it's a guide/reccomendation.

"If a great deal od depth of field is required, the aperture can be stopped down by one more stop without any substantial loss in sharpness."

That isn't exactly a guide. It is a pretty specific statement.