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08-17-2019, 01:36 AM   #1
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How to Set the Pentax Spotmatic F Lightmeter

Good morning!
Here I am with another question about my new Pentax Spotmatic F.
I took my camera with me on a long hike on Thursday and started to use it. I read many topics about how to set the light meter properly, and I thought I would be ok with it, but once in the field something was wrong with how the camera was exposing the scene.

My settings:
Lens (Pentax Super Takumar 55mm f/ 1.8) on AUTO with the switch on the side of the lens attachment in UP position.
The ISO dial was set to 200, which was the film box speed!
The needle in the viewfinder was responsive, moving up and down while moving the camera, so I assumed that it was working fine.

I took my Nikon FM along as well, to compare the metering information and I realised that the values given by the Pentax were inaccurate. I also noticed that the aperture blades in the lens were closing and opening only with the lens in manual mode, so I'm afraid I shoot the entire roll at f/1.8, even if I changed the aperture to f/8 and f/11 for many shots.

The battery: Energizer Epx625G Battery 1.5V, the one a local camera shop recommended to buy for the Pentax.

The question here is: assuming that the battery is the right one, did I make any mistake when setting the camera? If yes, could you please tell me how to set the lens (auto or manual ?) and the switch on the side (up or down ?) in order to get a god reading?

It will be super appreciate!
Ivan Di Marco. Landscapes on Film
Thanks!


Last edited by ivandimarco; 08-17-2019 at 01:55 AM.
08-17-2019, 05:15 AM   #2
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Hello,

About the lens: If it is set to Auto, when you push the pin you should see it closing. Set it at something like F8 and push the pin. It should stop down. Then the camera needs to push the pin with a little bar. Set the camera to a slow speed or bulb and see if the pin is pushed. As for the meter, I wouldn't be surprised if it is not accurate, especially if it hasn't been serviced in a long time. These cameras are already pushing close to 50 years old.

Thanks,
08-17-2019, 07:27 AM - 1 Like   #3
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second Ismael on the auto function not stopping down the lens......with the switch 'up' (as that's the position on the ES for stop down metering assuming the same on the F)) the viewfinder should get dimmer/brighter based on fstop in auto mode for the lens and you should also see the blades opening/closing looking at the lens
08-17-2019, 07:31 AM   #4
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If you're not already familiar with it, learn the "Sunny 16" rule - film ISO** = shutter speed @ f16 for open sun - and train your eye to estimate the proper exposure before you take a look at the camera meter.

** If you're shooting negative and like to overexpose a bit, then shutter speed equals whatever your effective ISO is, for example: film ISO = 100, effective ISO = 60, so open sun exposure will be 1/60 @ f16

Other "Sunny 16" factors:

"Snow/white sand" = f22
"Cloudy bright" (i.e. hazy) = f11
"Cloudy dull" (full cloud coverage, fairly gray) = f8
"Open shade" = f5.6
"Closed shade" = f4

08-17-2019, 07:36 AM   #5
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QuoteOriginally posted by ismaelg Quote
Hello,

About the lens: If it is set to Auto, when you push the pin you should see it closing. Set it at something like F8 and push the pin. It should stop down. Then the camera needs to push the pin with a little bar. Set the camera to a slow speed or bulb and see if the pin is pushed. As for the meter, I wouldn't be surprised if it is not accurate, especially if it hasn't been serviced in a long time. These cameras are already pushing close to 50 years old.

Thanks,
Thanks for your info.
About the lens: I followed your instructions and everything works fine. I set the shutter speed on 1 sec and the lens on auto. The blades opening/closing as you said and everything looks alright. So problem solved at least talking about the lens!

---------- Post added 08-17-19 at 07:42 AM ----------

QuoteOriginally posted by Aaron28 Quote
second Ismael on the auto function not stopping down the lens......with the switch 'up' (as that's the position on the ES for stop down metering assuming the same on the F)) the viewfinder should get dimmer/brighter based on fstop in auto mode for the lens and you should also see the blades opening/closing looking at the lens
Thanks for answering.
What is hard to get for me is why the Spotmatic has 2 different ways to expose the scene" stop down metering or through the switch 'up'.
Does it depend on the lens or just the situation? I downloaded the Spotmatic F manual but still, isn't super clear for me!

---------- Post added 08-17-19 at 07:58 AM ----------

QuoteOriginally posted by EarlJam Quote
If you're not already familiar with it, learn the "Sunny 16" rule - film ISO** = shutter speed @ f16 for open sun - and train your eye to estimate the proper exposure before you take a look at the camera meter.

** If you're shooting negative and like to overexpose a bit, then shutter speed equals whatever your effective ISO is, for example: film ISO = 100, effective ISO = 60, so open sun exposure will be 1/60 @ f16

Other "Sunny 16" factors:

"Snow/white sand" = f22
"Cloudy bright" (i.e. hazy) = f11
"Cloudy dull" (full cloud coverage, fairly gray) = f8
"Open shade" = f5.6
"Closed shade" = f4
Thanks for that.
I'm quite familiar with the "Sunny 16" rule, there are phone apps and hand held light meters as well, which I believe are even more precise.
I bought it as "in perfect working conditions" and I can still return it in case of issues. If there's a problem with the light meter I'm afraid I'll do that.
The whole point here is to understand if the camera works properly and since I'm not familiar with the system I'm trying to understand more here.
There are tones of information on the web but it seems to be a bit confusing.
08-17-2019, 09:29 AM - 1 Like   #6
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QuoteOriginally posted by ivandimarco Quote
why the Spotmatic has 2 different ways to expose the scene" stop down metering or through the switch 'up'.
Does it depend on the lens or just the situation?
I believe so.....the F, ES allow open aperture reading with specific lenses (purdy sure SMC or super multi coat is expressed on them) my lack of vocabulary says these lenses have a form of a 'bayonet' (resistor) as it can read the aperture in auto without stopping down but the meter adjusts accordingly but stops the lens down during the exposure......purdy sure metering takes place with a half depressed shutter with these lenses......the stop down switch (the one we are saying locked in the 'up' position) is for older lenses which do not have the so called 'bayonet' (resistor) for actual stop down metering...…

so yes and yes to the lens used yer questions........
reading the review(s) for the F may help in distinguishing the lenses
Pentax Spotmatic F - Pentax M42 Screwmount Film SLRs - Pentax Camera Reviews and Specifications


someone else may chime in and provide better clarity / explanation they have been helpful with my pursuit of film and the various bodies I use
08-17-2019, 09:46 AM   #7
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QuoteOriginally posted by Aaron28 Quote
I believe so.....the F, ES allow open aperture reading with specific lenses (purdy sure SMC or super multi coat is expressed on them) my lack of vocabulary says these lenses have a form of a 'bayonet' (resistor) as it can read the aperture in auto without stopping down but the meter adjusts accordingly but stops the lens down during the exposure......purdy sure metering takes place with a half depressed shutter with these lenses......the stop down switch (the one we are saying locked in the 'up' position) is for older lenses which do not have the so called 'bayonet' (resistor) for actual stop down metering...…

so yes and yes to the lens used yer questions........
reading the review(s) for the F may help in distinguishing the lenses
Pentax Spotmatic F - Pentax M42 Screwmount Film SLRs - Pentax Camera Reviews and Specifications


someone else may chime in and provide better clarity / explanation they have been helpful with my pursuit of film and the various bodies I use
I see.
My one is an old Super Takumar lens, so I'll have to use the switch in the UP position to allow the meter to read the scene properly.
Thanks for clarify!
08-17-2019, 10:16 AM   #8
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QuoteOriginally posted by ivandimarco Quote
I took my Nikon FM along as well, to compare the metering information and I realised that the values given by the Pentax were inaccurate
do you recall the difference between to 2 meters?

QuoteOriginally posted by ivandimarco Quote
I also noticed that the aperture blades in the lens were closing and opening only with the lens in manual mode
yes in manual the lens stops down or adjusts the fstop as you change it simultaneously

now with 'auto' switched on the lens the aperture will close down to the set fstop when the little pin on the rear is depressed......this is what Ismael said to check.....can be done without the lens mounted pressing it with yer finger.......sorry if this just repeating stuff already done......actually more interested in the metering difference you had in the field

08-17-2019, 02:02 PM   #9
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QuoteOriginally posted by Aaron28 Quote
do you recall the difference between to 2 meters?



yes in manual the lens stops down or adjusts the fstop as you change it simultaneously

now with 'auto' switched on the lens the aperture will close down to the set fstop when the little pin on the rear is depressed......this is what Ismael said to check.....can be done without the lens mounted pressing it with yer finger.......sorry if this just repeating stuff already done......actually more interested in the metering difference you had in the field
There are 2 sometimes 3 stops difference between the two. I started to think that it could be the battery (Energizer Epx625G Battery 1.5V) that isn't the proper one for the Pentax.
08-17-2019, 03:00 PM   #10
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dang that is quite a bit....is it generally in one direction where maybe some kinda compensation could made? like if 400iso gets similar to 200iso on the FM if it typically under exposes kinda thing.....
08-18-2019, 03:40 AM - 1 Like   #11
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QuoteOriginally posted by Aaron28 Quote
dang that is quite a bit....is it generally in one direction where maybe some kinda compensation could made? like if 400iso gets similar to 200iso on the FM if it typically under exposes kinda thing.....
Hi mate and sorry for my late reply!

I've checked the exposure reading this morning (BST) with both cameras, the Spotmatic and the Nikon FM.
I set the Spotmatic the way people suggested here in the forum and, pointing the cameras to a building out of my window, I've got a reading of 1/30 sec with the FM and 1/15 sec with the Spotmatic (both at f/8 and ISO 100). As you said, the FM meter tend to underexpose the scene so I assume is all good with the Spotmatic now.

I tried a couple of reading indoor and got the same gap (about a stop difference, with the Spotmatic overexposing the scene), sometimes even the same value.
What I'd like to do is to get a different battery (a friend suggested this particular one) for the camera and try if it can make the meter even more precise.

My settings with the Pentax Spotmatic:
Lens (Super Takumar 55mm f/1.8) in AUTO and switch on UP position.

Anyway, I developed the 2 rolls I shoot last Thursday and -surprise- all the images taken with the Pentax (on Kodak ColorPlus 200 overexposed at ISO 100) are spot-on in terms of colours and exposure. Some images taken with the Nikon FM (on AGFA APX 100) are underexposed.

I'll test the Pentax once again with a black and white roll, less forgiving than a colour negative, so I can really understand if the meter is ok, or not!

Sorry for such a long message and have a good day!
08-18-2019, 05:10 AM - 1 Like   #12
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Hello,

Glad to hear images came out great! Sounds like you are going in the right direction. It is all about having fun!

Thanks,
08-18-2019, 12:38 PM   #13
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QuoteOriginally posted by ivandimarco Quote
Anyway, I developed the 2 rolls I shoot last Thursday and -surprise- all the images taken with the Pentax (on Kodak ColorPlus 200 overexposed at ISO 100) are spot-on in terms of colours and exposure. Some images taken with the Nikon FM (on AGFA APX 100) are underexposed.
sweet! that's cool they turned out......be interesting to see any difference with the other battery.....also nice that they are metering much closer to one another
08-18-2019, 01:49 PM   #14
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QuoteOriginally posted by Aaron28 Quote
sweet! that's cool they turned out......be interesting to see any difference with the other battery.....also nice that they are metering much closer to one another
I've tried again this evening in low light conditions. Still, just one stop difference! Will keep you updated when the other battery will come!
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