"slow" MF lenses?

[noci]

recently had a discussion with a friend about the numeral "slowness" of MF lenses that many times show a max. aperture of 2.8 or so. it was always my impression that this does, in fact, directly compare to 35mm lenses as the f-stop is a relative value: hence, many MF lenses are indeed quite slow (due to design limitations and such, I gleaned from photo.net..)

what do you think? 😕

max

 

[mfogiel]

This is a fact of life - I only have ONE f2.8 Hasselblad lens, but I have 3 that are actually f5.6... This does not bother me most of the time, because I basically use MF as tripod operation - over Christmas I went out to shoot with a long lens and a 2x Mutar, and that makes a max f stop of 11.0 ! - on the other hand, I could stop down to f 90 - can you do that on a Leica ???

 

[ferider]

The way I think about it Max, is that a 6x6 80/2.8 lens has roughly
the same DOF as a 50/1.4 35mm lens (3cm vs 4cm at 1m distance
wide open).

Roland.

 

[noci]

so it seems indeed a true fact of "slowness".
nope can't do that with 35mm, but in my work stopping down is an alien concept, anyways 🙂

(ok, not with my MF folder... you got me... erm=)

m

 

[Bryce]

Slowness in terms of required exposure, yes. In terms of DOF, no, not slower. Making sense?

 

[sepiareverb]

The way I think about it Max, is that a 6x6 80/2.8 lens has roughly
the same DOF as a 50/1.4 35mm lens (3cm vs 4cm at 1m distance
wide open).

Roland.

I'm with you here Roland, but the rub is that two stop difference translates into using a faster film, which usually negates the effect of the bigger negative, or does so enough to make MF a bit of a wash for me. Bigger, heavier camera with slower lens or 35mm RF, getting (gasp! dare I say it?? 😉 ) nearly identical grain in the final print? I pick the RF.

I choose between MF & LF as I prefer to work with MF using slow films on a tripod, thus getting a larger negative with the finer grain.

 

[peterm1]

Any given f stop lets the same amount of light through to hit the film no matter whether its on a 35mm format camera lens or an MF camera lens - if it did not you could not use a hand held light meter successfully for both - they would have to make different light meters for different camera formats.

But this does not mean that any f stop has the same absolute size on different lenses or formats. For example in 35mm format f5.6 (say) is quite small in diameter on a wide angle lens like a 28mm lens, has a bigger diameter on a 50mm lens and is bigger still on a 135mm lens and so on.

All MF lenses should have larger diameter holes for any given f stop than their 35mm camera equivalents. For example you would expect a 135mm lens on an MF camera to have a bigger "hole" at f5.6 than a 135mm lens on a 35mm format camera. This should affect depth of field as a larger hole translates into less depth of field.

This I believe would also result incidentally in less diffraction for larger format lenses when stopped down. Ansell Adams would often use f stops like f64 or even smaller in his large format cameras. Physically f 64 is quite large by comparison with what it would be on a 35mm camera (assuming they went this small) because he used large format cameras. Such small f stops would not work successfully on 35mm lens as the tiny size of the hole that would be required, would make for huge diffraction of the light which degrades the image.

Least that is how I have always thought of it. Have I got it right you optics experts?

 

[chambrenoire]

The Norita 66 has a 80/2 lens! It's a Pentacon Six-clone.
Flickr examples

 

[furcafe]

The Norita is a precursor to the Pentax 67, but isn't a clone of the Pentacon.

The Norita 66 has a 80/2 lens! It's a Pentacon Six-clone.
Flickr examples

 

[Pherdinand]

peterm, technically you made a small mistake in your first sentence. "Any given f stop lets the same amount of light through to hit the film no matter whether its on a 35mm format camera lens or an MF camera lens" -
that should be light density, or light per unit area shouldn't it?
To expose 6x6 frame corerctly, you need the same light per unit area as for the same film in 35mm format, BUT, the total light hitting the 6x6 frame is more, since there is a larger area to illuminate.
I.e. the image circle of a 6x6 lens is larger than the image circle of a 24x36 lens, thus fior the same illumination, more light is let through the 6x6 lens.
This also explains why the same f/stop lens in MF must be physically larger than its 35mm equivalent.
This is especially visible for digital PS lenses where the sensor is so tiny that a small lens suffices.