Originally posted by rml63 I have read the reviews and some of the specs of this meter (I think I got the model # correct) it is the 478D I have been reading about.It seems this meter has DTS (data transfer system) in which you can some how down load your camera’s algorithm for metering into the meter so they are both on the same page so to speak? Is this correct?In the online brochure it states you should calibrate your meter to the camera buy taking shots of a grey card with the lens you most use and I assume making adjustments to the meter? Then I see a guy on youtube use the thing right out of the box not following any of the above steps.Could someone explain to me if the above steps are necessary and why they are necessary? I have tried to figure it out on my own but I am not having any success.ThanksMike
Hello Mike.
I have the Sekonik L-358, that is the previous generation, so I don't know if what I'm going to tell you will help you or not.
I have the option to calibrate my photometer, if needed. I've using my photometer during years so I have a bit of experience, but it doesn't mean that I am any expert.
The calibration of my photometer is way simpler compared to the DTS system. I just can set a kind of exposure compensation. At present I have my photometer set at -0.3EV, so this value have to fit all the cameras I have.
But why do you need to calibrate a photometer? As I understand, a photometer is factory calibrated. The problem is that your camera sure is not telling all the truth when you set the ISO. As far as I know, the K3-II's ISO is around 0.3EV below real ISO, but really not sure 100%. This is why my photometer is set to -0.3EV, to match my camera real ISO. I don't know in deep the DTS, but I think this is a kind of profile to make adjustements on your photometer's measures to match your camera.
As an example, let's suppose I have my K3-II and I make a measure with my photometer at ISO 100, let's suppose I get 1/100 & f4.0 on my photometer. But, as my camera ISO is fake, when I set ISO 100 on my camera, the real sensor ISO is 80, so I should set my camera at 1/100 & f3.5 instead of 1/100 and f4.0.
But this is more complicated than that, maybe my camera's ISO 200 is accurate, ISO 400 is not, etc. So this is what I understand DTS profiles correct. Every camera have some inaccuracies regarding ISO, that are fixed with a profile, but I think they should be small.
In my case, I don't have profiles, just a global adjustment. By experience I have found that setting -0.3EV adjustment on my photometer gives me accurate exposures, notice that this is not a really huge deviation.
How do I do such adjustments/calibration ? I have a SpyderCube, that I found very useful to get correct WB but also to get medium tones, shadow, highlights, etc. So I prepare a lighting, take a measure and take a pic of my spidercube, and see if the grey part of the spider cube is about in the half of the histogram, just that.
Notice that also your lens is not telling you the truth, photo lenses lose a bit of light. A 2.8 lens can be actually f3.2 or so. I think only cinema lenses gives you the real f. In my case, I have a K5 + DA 50-135 and K3-II + sigma 17-50 combinations. If I get a picture at the same ISO, speed and F settings, pictures are slightly differents in exposure/tone. Also, you shoud consider your RAW converter, that can be using a curse when it sets the tone of your picture.
Can I use the photometer without any calibration? I think you can, sure you get a small deviation, but this deviation will be always constant, that is, you'll notice always a bit of underexposure or overexposure. If it's the case, then you can think about calibrating it... or just forget about it and correct it in post. I made a calibration maybe once a year or once every two years, just to be sure everything is OK.
Maybe some other users can share it's experience with photometer's use and calibration.
Regards.
---------- Post added 11-01-20 at 09:26 PM ----------
Originally posted by TonyW For more information about the practicalities seek out tutorials by Joe Brady e.g.:
I learned a lot with this guy about measuring with photometers, mixing ambient and flash light, etc.
He also looks like a nice person.