Light meter - calibration

[greku69]

hi
how to calibrate light meter with camera ?
thanks
edit : 5D with L-358

[Pete]

You use the light meter to show you what the indicated exposure is for a given ISO/shutter speed.

On my one, I enter my preferred ISO and aperture, and it tells me what shutter speed to set.

Then you put our camera into manual mode and use the settings indicated by the light meter.

[greku69]

yes... I know that ...
but I hear that ISO 100 in 5D is real ISO 125, so that why you need calibrate light meter, or is it just bulls..t ?

[fxk]

In my never to be humble opinion, it really doesn't matter much if the published ISO does not exactly match ISO speed standards.

Assuming the not-tricky shot - a person in full sun, with the sun over the photographer's shoulder... basic box-camera sunny 16 type shot...

My theory is that if the camera produces a properly exposed picture (without any exposure compensation (EC) at any given setting, in any/all modes, then there is nothing really to calibrate. (use the histogram, and not your eyes to make the determination)

Now, if you are shooting full-tilt manual, and using an external meter, then that may be a bit problemmatic - but with the instant feedback of digital, and the histogram to guide you, one can dial in a little EC to match the camera up to the external meter.

The last possibility is if the camera, in any mode, basic or creative, does not properly expose the capture without EC, (histogram without highlights, or without shadows, or blown highlights) then it is time to send it back to Canon. Yes, one could use EC - but why should we have to?

[ronmayhew]

Check out these articles:

http://doug.kerr.home.att.net/pumpkin/Exposure_Calibration.pdf

http://doug.kerr.home.att.net/pumpkin/Exposure_Calibration.pdf

[Hermeto]

yes... I know that ...
but I hear that ISO 100 in 5D is real ISO 125, so that why you need calibrate light meter, or is it just bulls..t ?

Calibration compensation on L-358 is easy, but I am not sure that you want to do that..

Hold ISO1 and ISO2 buttons pressed while pressing Power button.
You should see CAL 0.0 on the screen.
Holding both ISO1 and ISO2 buttons pressed, turn the wheel for the desired compensation.

[Freff]

This might help,

Calibrating your flash meter

In a perfect world, all films, digital sensors, lenses, shutters and light meters would be on the "same page", and light metering would be an exact science. In reality, the performance of any of these devices cannot be assumed, plus light meters are set to slightly different calibration constants from their respective manufacturers. There is also the human factor, everyone will have their own opinion on what is a "correct" exposure based their eyesight. Since perception of light and color vary from person to person, judgment of exposure will vary also.

Most Sekonic meters have calibration and compensation features that let you fine tune your meter so you can be within 1/10 stop accuracy to suit your equipment and your eye. Whether you shoot film, digital or both, adjusting the meter is a simple, straightforward procedure.

To calibrate your flash meter, perform the following steps:
1. Choose a subject that contains highlights, shadows and mid tones.
2. Position the meter so it faces the camera from the subject’s position. Mount it on a light stand or tripod so it remains in a fixed location
3. Set the camera to its highest possible synch speed so any ambient light will not affect the meter’s reading. (Sekonic meters will “see” any ambient light that is present and able to affect exposure-even in flash mode)
4. Test-fire and adjust your lights so the meter displays an even-numbered aperture (no tenths)
5. Take your first test image by setting the camera to agree with what the meter shows.
6. Take additional test images by adjusting your camera’s aperture over and under by using the smallest aperture possible (usually 1/3 or ? stops) Do not move or adjust the lights.
7. With a digital camera, you can evaluate the exposures immediately. If you are lucky, the “perfect” exposure will be the one that exactly matched the meter. No adjustment will be needed. If you feel that an over or under adjustment is needed, use the meter’s calibration or compensation function to make your changes. Shoot another test with the adjusted meter.
8. With a film camera, shoot transparencies, and make sure that when the roll is processed it is not cut and mounted. (It is easier to view a strip of film than it is a box of slides) Evaluate the images on a light box, and adjust the meter if necessary. A second roll will confirm your adjustments.
Because the performance of electronic and mechanical devices can drift over time, it is advisable to perform this test every six months. Repeat this test if you are going to use a different camera. You may also check the ambient mode the same way with a constant light source. (Modeling lights work well) If you wish match the incident readings to a particular gray card, mount the meter in a fixed location and take your readings, taking care not to permit any stray light through the back of the meter. Shoot some test images and evaluate them as before. The Sekonic L-558 and L-608 meters have the ability to calibrate incident and reflected readings independently.

[greku69]

thanks guys
I find in meter manual that is possible to calibrate meter by holding down ISO1 and ISO2 and turn meter ON, but now I have to read this link from ronmayhew post :)

[SkipD]

hi
how to calibrate light meter with camera ?
thanks
edit : 5D with L-358

yes... I know that ...
but I hear that ISO 100 in 5D is real ISO 125, so that why you need calibrate light meter, or is it just bulls..t ?First of all, forget what you "have heard". All that you should care about is how YOUR camera works with YOUR meter.

Here's what I would do for the test (and you should realize that calibration of instrumentation is my business):
1) Put the camera into "M" mode and leave it there.
2) Use the handheld meter to measure the light in EVENLY LIT scenes. Avoid contrasty situations that could be even slightly tricky. Use several different scenes with different levels of lighting. Some could be indoors and some outdoors.
3) Shoot the scenes with the camera set to precisely what the meter tells you. While shooting the scenes, write down the settings you used and also what the "meter" in the viewfinder was indicating (centered, left of center, right of center, and by how much, etc.)
4) Process the images, and view them on a CALIBRATED computer monitor.
5) Make a determination as to whether or not ALL of the images are either properly exposed, underexposed, or overexposed. Throw out any individual images that are different from the pack in making this decision.
6) IF (and only if) all of the images in the pack are requiring a little more or less exposure, then you should make a tweak to the meter.
7) Repeat all of the above after tweaking the meter. One ALWAYS should make "as left" calibration tests after adjusting anything.

Study any differences between the handheld meter and the camera's meter.

You should realize that any work you do in lighting situations that are a bit tricky will take some skill that you may still need to acquire. That's why I suggested using evenly lit scenes for the calibration test. With the camera producing well-exposed images in evenly-lit scenarios you can trust the meter's calibration. Don't blame the meter's calibration when you get into the trickier situations and get not-so-good results.

[greku69]

when using meter in daylight meter and camera meter are most the time show the same reading and looking at histogram exposure is fine, but situation change when reading in low light and night scene, reading are different between camera meter and light meter...no matter what metering mode is setup on camera... so do I still need calibrate meter ??

[SkipD]

when using meter in daylight meter and camera meter are most the time show the same reading and looking at histogram exposure is fine, but situation change when reading in low light and night scene, reading are different between camera meter and light meter...no matter what metering mode is setup on camera... so do I still need calibrate meter ??I would say that you do NOT need to calibrate the meter, assuming the resulting images look good.

It sounds to me like you may need to learn a bit more about using a meter for the tricky situations. A night scene, for example, has a lot of "dark" that can easily fool a meter if it is not used correctly for the situation. A histogram can provide very confusing results in tricky situations (such as a lot of "dark" in the background) unless you thoroughly understand what a histogram is showing you. In other words, a histogram is NOT an easy-to-use light meter.

Just spend some time learning how to get the most out of your equipment in the trickier situations. That's how all of us old-timers got our experience - by doing and learning. In fact, as you might extract from my signature below, the process never quits.

Also, if you use your handheld meter in a studio flash situation, you may want to test the results - much in the way I described above - with the flash sources prior to any serious use where mistakes could be costly. For example, do the tests before a paid portrait shoot.

[greku69]

thanks SkipD ...
looks like your right ... well maybe after 40 years I will talking the same experience language :)
thanks all for help ...