New M7 user question

[namancio]

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I just bought a used M7 and paired it with Summicron 35mm ASPH. I load my own film from bulk film rolls and reuse film cartridges. This results is non-matching DX and loaded film speed (i.e 400 speed film on 100 cartridge). I understand that I can override the ISO selection by selecting it manually instead of using the DX setting in the camera. My question is; what should be displayed during the first few seconds of turning the camera ON? Right now, my camera displays what it read from the cartridge and not the manually selected value. Is this how it should be? This is my first Leica and rangefinder. Thanks!

[stevesurf]

I just bought a used M7 and paired it with Summicron 35mm ASPH. I load my own film from bulk film rolls and reuse film cartridges. This results is non-matching DX and loaded film speed (i.e 400 speed film on 100 cartridge). I understand that I can override the ISO selection by selecting it manually instead of using the DX setting in the camera. My question is; what should be displayed during the first few seconds of turning the camera ON? Right now, my camera displays what it read from the cartridge and not the manually selected value. Is this how it should be? This is my first Leica and rangefinder. Thanks!

 

Best of luck with the wonderful M7.

 

The DX reader behaves differently with non-DX encoded cartridges

 

With Cinestill non-DX encoded film and manually set to ISO 800, the power on sequence flashes "800" then the exposure comp LED keeps flashing.

 

With Lomography purple non-DX encoded and manually set to ISO 400, it flashes the upper limit of the ISO range, "5000" yet correctly meters on ISO 400 and the exposure comp LED keeps flashing.

 

The above is with both my M7s that contain the latest version of the DX reader. Both meter consistently.

 

We should probably put these results in the forum's Wiki page

[stevesurf]

I forgot to add one important suggestion. Periodically, you should cycle the ISO and Exposure comp dial wheels back and forth to make sure the contact is being made correctly. Sometimes doing this will have an effect on the DX reader and ISO setting.

[namancio]

Thanks for the response. For my specific situation, I loaded a retail TMax 400 but wants to shoot at 320. If I manually choose 320 on the dial, what should be displayed when turning the camera ON? I am assuming 320 to confirm the chosen ISO. My camera displays 400. Is this normal? Btw, now much to update the dx sensor and cle? I bought it used so no warranty. Thanks Steve!

[stevesurf]

Thanks for the response. For my specific situation, I loaded a retail TMax 400 but wants to shoot at 320. If I manually choose 320 on the dial, what should be displayed when turning the camera ON? I am assuming 320 to confirm the chosen ISO. My camera displays 400. Is this normal? Btw, now much to update the dx sensor and cle? I bought it used so no warranty. Thanks Steve!

 

My pleasure! With the ISO 320 manual setting it will flash "320" with most films, but keep in mind I've seen it flash other things with the "weirder" films like Lomo.

 

Try moving the ISO and exposure comp dial back 'n forth and try again. Then try other intermediate settings like 640 and 1250 and see if you get it to read those. If these show up as 800 and 1600, then your reader is one step off and needs repair. If it is consistent in being off, then all you need to do is just use the exposure comp and dial in an exposure offset to compensate.

 

I'm not sure how much the DX reader upgrade is and you'll be without the camera for about a month; perhaps more. I would not have this done by anywhere except Leica. Good luck!

[jrh68uk]

Curious about this, as I'd never tried setting another speed on a DX film with my M7.

 

Right now I have a DX-coded 100 ISO film in. Turn on and it flashes 100, of course. When I manually select any other ISO value it still flashes 100 when I turn it on. The meter is correctly using the manually selected speed, though, which can be seen by looking at the reading whilst selecting different values - it changes accordingly.

 

This makes sense. The flashing 100 is saying that the camera knows that it's an ISO 100 film and the flashing dot, visible when a non-DX ISO has been selected, is indicating that this rated ISO has been overridden.

[jrh68uk]

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... What's more, if I manually select ISO 100 then the flashing dot goes away. One division either side, or more, and it's back. So, it doesn't necessarily indicate that a DX film has been overridden with a manual value; it specifically indicates that it's been overridden manually with a value other than the rated one.

 

In summary, the displayed value upon switching on, as long as the DX code is properly readable, is the value of that DX code and not the manually selected ISO value.

[namancio]

Thanks Jason. That is exactly what I observed in my M7. I contacted Leica USA in New Jersey asking the same question. While they were not definite in the answer, I was told that they can update my DX sensor from the gold plated pins to the IR for free. Knowing that I will not have my camera for maybe a month or more if I send it in, is it a worthy update since I know now that my observation is normal and not a malfunction? Is a CLA advisable for a used M7 even if it appears to be working properly? Thanks!

[Michael Geschlecht]

Hello Everybody,

 

Welcome to the Forum.

 

If you hold a DX coded cartridge horizontally with the little nubbin between your thumb & index finger & look at the DX code printed on it:

 

The left-most little squares, top & bottom, are both silver or white. Always. They are electrical contacts.

 

If the positions 2 thru 7 inclusive of the entire top row is silver or white: That is the DX code for an ISO of 5000.

 

The bottom row is the number of exposures on the roll & the ACTUAL, as opposed to stated, ISO of the film in that cartridge.

 

The putting of actual, as opposed to stated, film speeds on each individual cartridge was done: When electronic shutters allowed for more precise exposure than had previously been available.

 

Best Regards,

 

Michael

[Michael Geschlecht]

Hello Everybody,

 

I would like to correct a typographical error in my Post written yesterday which is just above this:

 

The part that says: "the positions 2 thru 7 inclusive of the entire top row"

 

Should actually read: "the positions 2 thru 6 inclusive of the entire top row"

 

Best Regards,

 

Michael

[stevesurf]

Hello Everybody,

 

Welcome to the Forum.

 

If you hold a DX coded cartridge horizontally with the little nubbin between your thumb & index finger & look at the DX code printed on it:

 

The left-most little squares, top & bottom, are both silver or white. Always. They are electrical contacts.

 

If the positions 2 thru 7 inclusive of the entire top row is silver or white: That is the DX code for an ISO of 5000.

 

The bottom row is the number of exposures on the roll & the ACTUAL, as opposed to stated, ISO of the film in that cartridge.

 

The putting of actual, as opposed to stated, film speeds on each individual cartridge was done: When electronic shutters allowed for more precise exposure than had previously been available.

 

Best Regards,

 

Michael

 

I can't find anything about actual vs stated ISO for the canister codes.

 

Can you cite a graphic; all I found were the usual examples of #exposures, exposure and ISO like this:

 

DX Codes

Trick the DX sensor | New York street photography blog

[pico]

I can't find anything about actual vs stated ISO for the canister codes.

 

The last two bits are more accurately considered exposure latitude.

[Michael Geschlecht]

Hello Steve,

 

Under the reference "DX Codes" that you provided there is a section called "Exposure Margins". These numbers can be interperted in a number of ways. For example:

 

+/- 1/2 of a stop is for films like now departed Kodachrome.

 

This can be interperted to mean that: The stated number is PRECISELY the actual ISO of this film & that there is a very limited margin for error in exposure. The ISO 64 stated on the cartridge is accurate.

 

+/- 1 stop can be interperted to mean that the speed on the cartridge (ie: Ektar 100) is the correct speed with a SMALL margin for error in exposure. The ISO 100 stated on the cartridge is accurate.

 

+2/-1 stops can be interperted to mean that the ACTUAL film speed is 3/4 of the stated ISO with a +/- of 1&1/2 stops of exposure latitude. Example: ISO 100, +2/-1 translates to an ISO 75 with a exposure latitude of 1&1/2 stops in either direction. A MEDIUM margin for error in exposure determination.

 

+3/-1 stops can be interperted to mean that the ACTUAL film speed is 1/2 of the stated ISO With a +/- of 2 stops of exposure latitude. Example: ISO 100, +3/-1 translates to an ISO of 50 with an exposure latitude of 2 stops in either direction. A LARGER margin for error in exposure determination.

 

All of the above is for normal development with the chemicals, times & temperatures suggested for the NOMINAL ISO stated on the cartridge. Do NOT change any chemicals, times or temperatures.

 

Best Regards,

 

Michael

[Michael Geschlecht]

Hello Again Steve,

 

Just another thought:

 

Any given film, whether color, B&W, negative or transparency, only has 1 ISO that produces the best image quality. Given the same chemicals, times & temperatues during development.

 

What some film manufacturers sometimes do is "tweak" their stated ISO's on the film's carttridge. Sometimes, there is a sort of "horsepower race" in terms of trying to make films SEEM to be more able to record images in less light.

 

These higher NOMINAL ISO's on cartridges are still accurate because they fall within the film's ACTUAL latitude.

 

With the advent of more accurate electronic shutters in the 1980's film manufacturers decided to include the above information so that the rudimentary computers in the cameras with these electronic shutters could take the ACTUAL ISO & the film's ACTUAL exposure latitude into account when determining exposure.

 

When a person sets the ACTUAL ISO & bypasses the DX coding: They have a greater degree of freedom of choice in determing what exposure to use within the now more clearly understood parameters of the film's actual latitude.

 

Best Regards,

 

Michael

[pico]

Regardless of this last two bits of latitude, is it read or used by the M7? For example, if you nudge the ISO dial so that it is still within the latitude, does the finder still blink at you?

.

[stevesurf]

The last two bits are more accurately considered exposure latitude.

That makes sense, now, thanks.

 

Regardless of this last two bits of latitude, is it read or used by the M7? For example, if you nudge the ISO dial so that it is still within the latitude, does the finder still blink at you?

.

 

Yes, it does; I tried rotating the ISO dial to the first available detents and well within Portra 400's latitude, 320 and 500 and it blinks away. As someone once stated, it doesn't take very much to get it blinking.

 

Hello Again Steve,

 

Just another thought:

 

Any given film, whether color, B&W, negative or transparency, only has 1 ISO that produces the best image quality. Given the same chemicals, times & temperatues during development.

 

What some film manufacturers sometimes do is "tweak" their stated ISO's on the film's carttridge. Sometimes, there is a sort of "horsepower race" in terms of trying to make films SEEM to be more able to record images in less light.

 

These higher NOMINAL ISO's on cartridges are still accurate because they fall within the film's ACTUAL latitude.

 

With the advent of more accurate electronic shutters in the 1980's film manufacturers decided to include the above information so that the rudimentary computers in the cameras with these electronic shutters could take the ACTUAL ISO & the film's ACTUAL exposure latitude into account when determining exposure.

 

When a person sets the ACTUAL ISO & bypasses the DX coding: They have a greater degree of freedom of choice in determing what exposure to use within the now more clearly understood parameters of the film's actual latitude.

 

Best Regards,

 

Michael

 

Thanks very much Michael, this is great information.

[namancio]

Thank you all for the replies. Great information especially for someone coming from digital where ISO is mainly taken for granted.