Why do 120RF's have slow lenses?

[sevo]

Yes and the larger the lens' maximum aperture, the more difficult it is to incorporate a leaf shutter that works at reasonable speeds. Of course, nothing says a 120 RF must have a leaf shutter.

The run-down times of large focal plane shutters are nothing to write home about - indeed they often are beyond limits where shake-induced motion distortion can grow into a visible problem if you don't use a tripod. My Makiflex (6x9), probably the last 6x9 with FP shutter, and the last 6x9 SLR along with the Arca, has a whopping 1/15s X sync. Even the most modern FP shutter medium format cameras are fairly moderate size and nonetheless quite slow by 35mm standards (where X times below 1/125 became extinct by the eighties) - Mamiya managed to achieve a reliable 1/60s on the M645 series, Hasselblad a not as reliable 1/90 on the 1/3 bigger but somewhat finicky 2000 series shutters.

 

[bensyverson]

It's a great shame no one resurrected the Ermanox.

Oh, great. Just great. Right when I think I'm immune to GAS, you go and find something ultimately drool-worthy that goes for over $2000!

 

[Jamie123]

The run-down times of large focal plane shutters are nothing to write home about - indeed they often are beyond limits where shake-induced motion distortion can grow into a visible problem if you don't use a tripod. My Makiflex (6x9), probably the last 6x9 with FP shutter, and the last 6x9 SLR along with the Arca, has a whopping 1/15s X sync. Even the most modern FP shutter medium format cameras are fairly moderate size and nonetheless quite slow by 35mm standards (where X times below 1/125 became extinct by the eighties) - Mamiya managed to achieve a reliable 1/60s on the M645 series, Hasselblad a not as reliable 1/90 on the 1/3 bigger but somewhat finicky 2000 series shutters.

Yes, but you can't have it all. Either large apertures or fast flash sync.

 

[sevo]

Yes, but you can't have it all. Either large apertures or fast flash sync.

Slow rundown does not only mean slow flash sync, you'll also get distortion on moving objects, or even from camera shake.

 

[Brian Legge]

I imagine the size of the lens would be rather large for an RF - not to suggest some of those cameras are exactly small themselves. 😉

 

[Bob Michaels]

Sorry if this has been asked before. maybe i should've asked: why doesn't the 7 system have faster lenses? TLRS and waist level cameras have relatively fast lenses in comparison. There are also cameras, like the Plaubel Makina, which also has a faster lens.

Personally I believe the lack of fast glass for the Mamiya 7 is because Mamiya concluded there was not sufficient market to justify the development cost. I think Mamiya concluded their customers valued optical quality, weight and cost over lens speed. You can compensate for an f4 lens with a tripod or flash but there is no way to get around weight / optical quality / and cost. Remember the development has to be recovered by a combination of sales price and number of units sold. It is possible that it just cannot be done.

Sometimes we suffer from unrealistic expectations. We say we wish they would make a lens a stop faster but then will not buy it when we find out it is twice as big, twice as heavy, and costs twice as much. Example, compare the number of f2.0 vs f1.4 35mm lenses.

 

[Roger Hicks]

Personally I believe the lack of fast glass for the Mamiya 7 is because Mamiya concluded there was not sufficient market to justify the development cost. I think Mamiya concluded their customers valued optical quality, weight and cost over lens speed. You can compensate for an f4 lens with a tripod or flash but there is no way to get around weight / optical quality / and cost. Remember the development has to be recovered by a combination of sales price and number of units sold. It is possible that it just cannot be done.

Sometimes we suffer from unrealistic expectations. We say we wish they would make a lens a stop faster but then will not buy it when we find out it is twice as big, twice as heavy, and costs twice as much. Example, compare the number of f2.0 vs f1.4 35mm lenses.

Dear Bob,

Oh, you cynical (and realistic!) fellow.

Cheers,

R.

 

[Bob Michaels]

Oh, you cynical (and realistic!) fellow.

Roger: are you implying "there ain't no such thing as a free lunch"?

 

[tlitody]

did somone mention the hassy FE lenses

http://www.mir.com.my/rb/photography/companies/nikon/hasselblad/lenses/felenses/fe_lenses.htm

but do you really need fast MF lenses. I mean an 80mm lens on a 6x6 neg gives about twice the field of view than on a 35mm camera at same distance so you have to get half the distance to the subject which means you reduce the dof for the same framing at the same fstop. So the only reason you would need faster glass is in low light hand held work which has never been the forte of MF as far as know.

 

[Thomas78]

Yes and the larger the lens' maximum aperture, the more difficult it is to incorporate a leaf shutter that works at reasonable speeds. Of course, nothing says a 120 RF must have a leaf shutter.

You are right, but for a dedicated low light lens I would accept a 1/250 or 1/200 s as the fastest speed which would allow a leaf shutter with more diameter allowing a lens with higher maximum aperture.

Concerning the DOF discussion, I think that with a good rangefinder it would be possible to focus a 80 mm lens at f2.0 or a 105 mm (6x9) at f2.8:
(For the conclusion see the end of this post)

Some calculations for the DOF:
(done with the tool on
http://www.erik-krause.de/schaerfe.htm
sorry, this page is in german, but since the math behind optics ist the same, other pages/tools should give the same results)

for the comparison of 35 mm vs. 120 Film:

35 mm --> 24 x 36 mm

120 6x6 --> 56 x 56 mm
120 6x9 --> 56 x 84 mm

To compare the different aspect rations, lets assume we want to take a picture of an object with an area of 1.5 m^2:

--> 24 x 36 mm and 56 x 84 mm --> 1 m x 1.5 m

--> 56 x 56 mm --> 1.22 m x 1.22 m

for 24 x 36 mm and f= 50 mm: focus at 2.14 m

with circle of confusion of 0.025 mm

f/2.0: DOF 2.05 - 2.23 m : 0.958 - 1.042 of focus distance
f/1.4: DOF 2.08 - 2.20 m : 0.972 - 1.028 of focus distance
f/1.0: DOF 2.10 - 2.19 m : 0.981 - 1.023 of focus distance

for 56 x 56 mm, the same image sharpness would allow a circle of confusion of 0.046 mm,
with f= 80 mm and focus at 1.82 m (or the same object area of 1.5 m^2) we get:

f/2.8: DOF 1.76 - 1.89 m: 0.967 - 1.038 of focus distance
f/2.0: DOF 1.78 - 1.87 m: 0.978 - 1.027 of focus distance

for 56 x 84 mm and a circle of confusion of 0.058 mm we get with f = 105 mm and focus at 2.00 m:

f/2.8: DOF 1.95 - 2.06 m: 0.975 - 1.030 of focus distance
f/2.0: DOF 1.96 - 2.04 m: 0.980 - 1.020 of focus distance


If you accept the same image quality in respect to sharpness reduction due to DOF issues, a 50 mm lens for 24x36 mm at f/1.4 gives a comparabel DOF to a 105 mm lens for 6x9 at f/2.8 or a 80 mm lens for 6x6 at about a bit above 2.0.

If you expect a higher image quality at MF, you have to restrict yourself in the use of large apertures...

 

[Roger Hicks]

Roger: are you implying "there ain't no such thing as a free lunch"?

Dear Bob,

That's part of it. The other saying that comes to mind is centuries older: "If wishes were horses, then beggars might ride."

Cheers,

R.

 

[graywolf]

The lens is not so hard. The shutter is doable. The rangefinder too. I had a Mamiya Universal Press with a 100/2.8 that covered Polaroid (3-14 x 4-1/4), & 6x9 film. Of course it weighed six pounds, and no one has pockets big enough to carry it in. It is probably the camera I miss the most.

 

[patrickhh]

Mamiya made a 55mm f2.8 leaf shutter lens for the 645 line as well.

There's also a 90/2.8 LS for the Pentax 67. And it's not even big or expensive. 😉