What does ROM do?

[randall_shafer]

OK, I'm game. I've looked over the Leica catalog to find out what

function the ROM contacts perform on the latest R-series lenses, to

no avail. I haven't been able to find anything on the net, either.

 

Since the conventional cams transmit aperture information to the

body, I've got to guess that the contacts send information on the

focus distance setting to the TTL flash electronics, and perhaps

identify the focal length and/or zoom setting of the lens.

 

Apparently Leica wants the ROM contacts to be some kind of mysterious

inducement to buy newer lenses because they don't mention their

function in the catalog.

 

Does anyone know what they do?

[chip l.]

Check out the Leica FAQ

 

http://www.nemeng.com/leica/001c.shtml

[lucien1]

Randall,

 

With ROM, the R8/R9 will know before firing what will be the real aperture (including vignetting which is different at each aperture and on each lens) in order to calculate more precisely the exposition.

With lenses without ROM, the camera will give an average result.

 

Leica said also that small lenses with ROM permit shorter time parallax than bigger because, thanks to the ROM, the camera knows the exact delay before the diaphragm is closed and can start earlier the process of firing.

With a 280/2,8 at f8 it will be longer than with a 19/2,8 at same aperture, or than with the same 280/2,8 at f2,8.

With lenses without ROM, the camera will always choose the longest delay.

 

With the APO-Extender 2X ROM (#11 269) the viewfinder will display the real (resulting) aperture if used with a ROM lens, and the camera will know the new focal length of the lens (or zoom) and move the flash head accordingly.

 

By the way, ROM are passive. They don't calculate anything.

It's the camera which will calculate thanks the info stored at the factory inside the ROM.

At the end of manufacture, or when retrofitting of older lenses, every Leica-R lens is individually measured and programmed in order to make sure that the potential accuracy of the exposure metering is maintained at each aperture. Two identical lenses may have different ROM's information inside.

 

If, after the lens left the factory, there is a problem with the diaphragm mechanism, the ROM will NOT know it.

 

All the information I give you here are coming from Leica Fotographie (7/98) on pages 30 and 31 and confirmed by Leica technician answers to the question I've asked during my visit in May 2001 at the Solms factory.

 

What I'm saying about the ROM Apo-Extender 2X (and it's the same with the macro-adapter ROM) is from my personal experience with those accessories used with ROM lenses.

 

May I add that not all the zooms with ROM are making the flash head zooming. The Vario-Apo 70-180/2,8 and 105-280/4,2 are only locking the flash head on the minimum focal length. As an example: the ROM of the 70-180 will lock the flash head on 70mm. And a 70-180 ROM + APO 2 X ROM will lock the flash head on 105mm. No zooming. But on the other hand, they are the only Leica zooms that you can send to the factory in order to have the ROM added.

 

Regarding the improvement in accuracy, the correction of the exposition is made via the steps of the R8/R9 shutter, not by the diaphragm.

 

Lucien

[Robin Smith]

Randall

 

It does not do much apart from giving focal length indication to the cameras CPU which only affects the flash head setting of compatible Metz flashes (with zoomable heads). It also passes aperture info to the camera too - for example when using the 2 x or 1.4 x converters the ROM connections allows the v/f aperture read out to be corrected automatically for the exposure factor. So when you set the aperture on, say, the 100mm Apo Macro to f2.8 with the 2 x (ROM) converter the aperture readout says f5.6 (which is correct as there is a 2 stop loss by using the converter), not the lens' actual f2.8. But of course you can use a 3rd cam lens just as well with converters, but the v/f aperture display will not be correct. Leica also I suspect designed the ROM system because one day they think they will use this system for transferring focus and aperture info to the camera and an electronic system is (arguably) a more elegant way of doing this than using the physical cams. But in practical use, apart from the flash head setting, it does nothing very useful at present.

[jay_.]

<<With ROM, the R8/R9 will know before firing what will be the real aperture (including vignetting which is different at each aperture and on each lens) in order to calculate more precisely the exposition. With lenses without ROM, the camera will give an average result.>>

 

This is pure baloney. The 3rd cam tells the meter what aperture the lens is set at before firing just as well as the ROM does.

 

I had both ROM and non-ROM lenses with my R8's and there was no difference in exposure. Even with slide film, anything less than a 1/3-stop is not discernable, so precision above that level is a waste. In real-world usefulness all the ROM does is zoom the head of a flash to match the focal length, and since no Metz flash has a zoom setting longer than 105mm, ROM on any lens longer than that is a total waste.

[lucien1]

Ah Jay !

 

Still a non-believer.

 

;-)

 

Lucien

[lucien1]

Jay,

 

<<The 3rd cam tells the meter what aperture the lens is set at before firing just as well as the ROM does.>>

 

No, not as well according to Leica.

 

<<I had both ROM and non-ROM lenses with my R8's and there was no difference in exposure. Even with slide film, anything less than a 1/3-stop is not discernable, so precision above that level is a waste.>>

 

I don't have identical lenses, with and without ROM, to make a honest comparison.

 

;-)

 

<< In real-world usefulness all the ROM does is zoom the head of a flash to match the focal length, and since no Metz flash has a zoom setting longer than 105mm, ROM on any lens longer than that is a total waste.>>

 

When using a 180 mm, I much prefer that my Metz zoom to 105 than staying on 35.

 

With an Apo-Extender, it's nice, but not vital, to see the correct aperture in the finder.

[jay_.]

<<I don't have identical lenses, with and without ROM, to make a honest comparison. >>

 

Put a thin piece of cellophane tape over the ROM contacts.

[lucien1]

Jay,

 

You did it, I presume ?