can the design of a lens affect a light meter?

Mick Fagan · Dec 28, 2016

Ces1um said:
Now should I stick with the light meter app on my phone or should I buy a handheld meter? Suggestions?

Until yesterday, I would not have known, but yesterday I met up with a young photographer. During our discussions, the subject of light metering came up, he was wondering the exact same question, should he purchase a genuine light meter, or continue using his mobile phone meter application to advance his film photography.

I pulled out my Gosson Profisix light meter, which I know is reasonably accurate and we compared meters.

His phone application meter and the Gosson meter, were, for all intents and purposes, giving identical information on a wide variety of subjects. I was very impressed with the accuracy of his meter and suggested that he keep on using the application meter in his phone as it seemed perfectly alright.

Save your money for now and keep using your phone meter. To settle your mind, place a normal lens on your camera and take some careful light readings with the camera, then do the exact same with your phone meter. If they are very close, or even identical, you can rest assured that you will be alright with taking light readings with the phone meter.

Mick.

Ricardo Miranda · Dec 28, 2016

Theo Sulphate said:
However, lever (ii) is a coupling that the body needs to determine the maximum aperture of the lens and also read the selected aperture on the aperture ring. With that information, the meter can give an accurate wide-open reading.

That is correct Theo.
For those that use M42 lenses on a Pentax K body would know that the adapter made by Pentax will push that lever (ii) fully to the right as you see the mount from the front of the body. That prepares the meter for stop-down metering as a normal Super or SMC Takumar would have means to stop down the aperture to the taken position by means of a sliding switch and so the Pentax K1000 is able to do stop-down metering with a M42 lens.

It seems to me that the Russian "Art" lens is missing a way to push the lever on the body to the "stop-down" position as the M42 to Pentax K adapter would do.
It would have been better if they had made a M42 lens in this case.

MattKing · Dec 28, 2016

Theo Sulphate said:
Below is a Pentax K mount lens. Lever (i) is used by the camera body to stop the lens down during exposure - obviously your art lens won't have that since you manually insert the aperture. However, lever (ii) is a coupling that the body needs to determine the maximum aperture of the lens and also read the selected aperture on the aperture ring. With that information, the meter can give an accurate wide-open reading. If your art lens doesn't have lever (ii), then your meter won't read correctly with that lens. In that case, the reading from your original K lens should be used.

http://www.pentaxforums.com/content/uploads/files/77/p1463/K.jpg

Thanks for the photo Theo.
What I find confusing is the fact that the camera's manual indicates that you can use the K1000 with stop down metering.

EDIT: I think Ricardo's post may have explained the situation.

Ces1um · Dec 28, 2016

Theo Sulphate said:
Actually, grussmir mentioned it first in post #6, but having a photo of the mechanism helped.

I stand corrected. Thank you grussmir!

Jim Jones · Dec 28, 2016

Perhaps Ces1um can use the camera's meter by determining an exposure correction for each aperture plate and make an exposure correction chart.

flavio81 · Dec 28, 2016

Lazy lens designers! Not only they don't bother to fit a proper iris mechanism, they also don't put the minimal effort to place the open aperture signal on the mount!!

That's why I don't care too much for Lomography's artsy lenses.

Lomography should make a 120-size version of the LC-A, that would be a sales hit (they got very close to building such thing, not so long ago...)

Theo Sulphate · Dec 28, 2016

flavio81 said:
...
Lomography should make a 120-size version of the LC-A, that would be a sales hit (they got very close to building such thing, not so long ago...)

There is a Lomo LC-A 120 at Blue Moon (even though they indicate it's out of stock).

Ces1um · Dec 28, 2016

flavio81 said:
Lazy lens designers! Not only they don't bother to fit a proper iris mechanism, they also don't put the minimal effort to place the open aperture signal on the mount!!

That's why I don't care too much for Lomography's artsy lenses.

Lomography should make a 120-size version of the LC-A, that would be a sales hit (they got very close to building such thing, not so long ago...)

The design of interchangeable aperture plates rather than an iris was deliberate. It provides a "retro aesthetic" and also allows for a somewhat gimmicky bokeh control- where the aperture plates can have different shapes other than a single hole. The open aperture signal would have been nice though. They do make a 120 version of the lca called the LCA 120. It's just under 500 cdn to purchase.

AgX · Dec 29, 2016

At least with one middle of the road lens you can quite easily use selfmade stops too: Helios 44.

grussmir · Dec 29, 2016

Ces1um said:
I stand corrected. Thank you grussmir!

...you're welcome, but since I'm not a native speaker, it seems I was unable to properly express my thoughts. An image says more than 1000 fuzzy words I guess
The correction value for the meter can easily be obtained, it should be somewhere close to f22-fXX (your working aperture)... but this doesn't help, since their is no exposure compensation able to fit that range. I must affirm ces1um: The open aperture signal would have been nice though. Some people would call it obligatory for a fully functional lens... but don't know how the Lomo-Crowd calls it

GarageBoy · Jan 2, 2017

Is that a Pentax only thing? With Nikon ai and non ai cameras, it doesn't matter

RalphLambrecht · Jan 3, 2017

Ces1um said:
I recently purchased lomography's new daguerreotype art lens in K mount. This is a beautifully crafted lens but I've hit quite a snag with it. Let's say I have a different lens on my k1000 and work out my exposure settings. For arguments sake let's say these settings are F4 1/125. If I then put my daguerreotype lens on and the F4 aperture plate in, the light meter now says the shot is underexposed. Radically underexposed. Now for this to work my settings are F4 1 second exposure. An independent light meter confirms the F4 1/125 to be correct.

Any idea what could be going on here? To confirm, I am using the correct F4 aperture plate. This issue persists with all apertures. The lens itself seems to be affecting the meter. These aperture plates are located in front of the element which is different from all other lenses I own. My question is- do I trust my light meter with the lens on, or do I trust my external light meter? Any help would be appreciated.

in photography everything affects everything else and final results depend on the current position of heavenly bodies in the sky at the precise moment of exposure in relation to your dog's birthday.

Theo Sulphate · Jan 3, 2017

GarageBoy said:
Is that a Pentax only thing? With Nikon ai and non ai cameras, it doesn't matter

With Nikon, the camera's meter still needs to know the speed of the lens (max aperture - because Nikons meter wide open) and it also has to know the selected aperture (which is what the lens will stop down to at the time of exposure).

In pre-AI days, you told the camera what the max aperture was by doing the twist-twist ritual on the aperture ring every time you mounted a lens. On a Nikon with a metering head, a window would confirm the max aperture. As you selected different apertures on the ring (the lens still being wide open), the prong on the lens told the body what aperture was being selected.

With AI lenses and later, the auto-indexing (AI) ridge automatically told the camera what the max aperture was when you mounted the lens.

If the OP were using a Nikon with that lens, he'd still have to convey information to the body/meter that the lens was stopped down rather than wide open.

benveniste · Jan 3, 2017

Ces1um said:
Now should I stick with the light meter app on my phone or should I buy a handheld meter? Suggestions?

When I compared the "Pocket Light Meter" app to my Minolta Light Meter, I rarely found a difference of even 1/3rd of a stop. Until and unless you want an incident meter, I'd suggest using the phone and seeing how it works out.

Ces1um · Jan 3, 2017

benveniste said:
When I compared the "Pocket Light Meter" app to my Minolta Light Meter, I rarely found a difference of even 1/3rd of a stop. Until and unless you want an incident meter, I'd suggest using the phone and seeing how it works out.

I'll download one then and give it a try! Thanks for the help!

can the design of a lens affect a light meter?

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