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03-17-2014, 08:31 AM   #1
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Digital Spotmeters and DSLR metering

Hi all,

I have a lot of legacy glass (see signature) and I often find exposure a bit of problem when I use them on my digital cameras. Yes, I am aware of the green button and its use on a digital camera with an M or K series lens attached. I have used the green button a lot and still continue to have more exposure failures than I would like.

I was wondering if the are any users out there who have used a spotmeter to deal with exposure issues while using Pentax legacy (Takumar, K, M series) glass on their digital cameras. I can't help but think it would be useful especially when using longer lenses for birding. I imagine that one degree spot might not be fooled as often as the green button seems to be when I'm trying to nail exposure of a bird in the bushes. I'm just speculating of course but I would like some feedback from those who have had some experience with spotmeters in such conditions.

In particular I would like to know if the spotmeter is more accurate than using the green button?

Is it quicker to use than the green button?

Any other observations, pros/cons you may have regarding the use of a spotmeter with a digital camera.

Tom G

03-17-2014, 09:44 AM   #2
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1 degree spotmeters are specialty items. I have one.

Is it quicker to use than the green button?


A better question might be, "How narrow is central spot metering on modern Pentax DSLRs."
03-17-2014, 10:09 AM   #3
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I have a Pentax Digital Spotmeter, it isn't really quick to use because it only displays EV in the viewfinder and unless you have the values memorized you have to consult the calculator. I typically only use it when I have time to be slow and really analyze the shot.

It is mostly accurate, though there is always a little variation depending on lens since one lens at f2.8 might not transmit the same amount of light as another.

The green button is usually accurate enough for me, though I have changed the focusing screen to one that has a more linear light response.
03-17-2014, 11:18 AM   #4
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QuoteOriginally posted by 8540tomg Quote
In particular I would like to know if the spotmeter is more accurate than using the green button?
Different is the word.

The stop-down (green button) metering should be essentially accurate* with your K-5 in M mode and much less so with your K10D. Neither camera will meter reliably with M42 glass in Av mode. If you are unhappy with your results an external meter may be a good option.

That being said, let's get back to the spot meter. Here are a few discussion points as applied to a spot meter vs. hand-held vs. TTL meters:
  • Spot meters are not magic
  • Spot meters are not better per se, and when used improperly may actually result in badly exposed shots
  • The spot meter is a specialized tool that is used to measure reflected light values from a specific portion of the subject, though care should be taken to remember that the reading will result in a middle value on the final image
  • A spot meter, when properly used can allow for fine control when placing the original exposure with the intent for massaging the image later in processing
  • A regular hand-held meter may be used in a manner similar to a spot meter if you are able to take readings close in on the subject
  • The above point also applies to the in-camera meter
  • The in-camera TTL meter has the advantage of automatic compensation for light absorption by the lens glass and any filters
  • All three are essentially accurate in that they can be used to determine an appropriate exposure
There is at least one user on this site (Tuco) who is a regular spot meter user. He uses it primarily for his medium and large format film photography.

QuoteOriginally posted by 8540tomg Quote
Is it quicker to use than the green button?



* Accurate in the sense that metering off an evenly lit, neutral target (say a blank inside wall) will result in equivalent mid-range value distributions in the histogram at all apertures with all lenses.

(...almost never uses the spot meter feature on the camera's that have it...)

Last edited by stevebrot; 03-17-2014 at 11:29 AM.
03-17-2014, 01:34 PM   #5
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Original Poster
Thanks guys,

I guess I was looking for a magic bullet that doesn't exist.

I've considered getting a digital spotmeter for years but it seems it would just be another gadget

in the seldom used pile if I did. I guess I'll just go back to the old trial and error method. At least it's a lot cheaper on

digital than it used to be on film.

Tom G

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