Calibrating you camera's iso and your meter

[Keith_Strickland]

I appreciate that with raw AND a consistant workflow with for instance commercial studio product photography could be important but I gather that the prevailing wisdom throughout many photography sites is that with say studio portrait photography where there should not be any variables in the exposure or the white balance that the use of Raw over Jpeg is very rare as the workflow involved contains just too many steps to make it worthwhile,that is not to say that you are doing it wrong but that your methods work for you but they are not the only method used.
Your use of the meter analagy is also flawed as with studio lighting it is essential that you use an incident light meter in order to get wrap around lighting and also to enable the use of lighting ratios,this enables the photographer to have a consistant light source that he can use for volume style work..would I be right in saying that your use of Raw capture is because it gives you more latitude with the exposure etc..rather like neg film as opposed to trannies which has less latitude much like digital capture?
KK

[Jonathan_Wienke]

Keith, I shoot close to 100% RAW for several reasons:

1. Increased dynamic range. When shooting JPEG, you are typically throwing away 1-2 stops of the dynamic range that can be captured by the sensor. With many subjects, this makes the difference between having or not shadow & highlight detail. This also gives one more latitude to gracefully recover from exposure errors, but it is always preferable to expose properly in the first place.

2. Greater color consistency and accuracy, and totally flexible white balance adjustment. I use ACR for RAW conversion, and have the calibration settings adjusted to maintain a consistent "look" and accurate colors with each of my 3 bodies (1Ds, 1D-MkII, and 10D). If the AWB "As Shot" setting isn't quite what is desired, one can adjust white balance to taste (including color adjustments done for creative reasons and not for strict color accuracy) and apply that to any number of RAWs. Then the RAWs can be converted en masse with a simple action. Properly done, a RAW workflow can have fewer steps and a greater degree of automation than an equivalent JPEG-based workflow.

3. Higher image quality. Those extra bits in the RAW really do make a difference. In addition, RAW converters can use more sophisticated and CPU-hungry image processing techniques than can be done in-camera. And external RAW converters offer additional features like vignetting and CA correction that cannot be done in-camera.

I don't own, and have no interest in purchasing a flash meter. With digital, you can get all the information you need by taking a "polaroid" shot and looking at the histogram and the shot itself. And setting flash ratios has nothing to do with metering technique. I have total control over flash ratios whether using Canon's wireles E-TTL or using studio strobes where the power is set manually. WHether or not I have a flash meter is irrelevant.

[KevinCarter]

Can't speak for others but for me, Raw is for high end jobs, very important work, Jpegs is for lower end, not so critical work -- however you want to define that.

My original question had nothing to do with Raw/jpeg debate-- more about the certainty of weather or not your meter readings match your lens f stop readings.

[George_Lund]

I used to feel the same way about flash meters, didnt have one, didnt want one...... then I read Scott Smiths book on studio lighting, borrowed a flash meter, tried it his way, bought a flash meter, made my entire work flow easier and with better results, just my 2 cents.

[Will_Perlis]

"...more about the certainty of weather or not your meter readings match your lens f stop readings."

About the best you can do is change the meter's ISO (or calibration bias with a Sekonic) so its readings of a scene match the settings that give you a good picture (whatever "good" means to you) in a shot taken in carefully adjusted manual mode.

The sensitivities across the spectrum are going to be more or less different for the two so precise correspondence isn't possible under all lighting conditions by just varying the ISO or calibration bias.

You can do the gray card matching routine and force the meter to agree with the camera's readings, but that won't tell you anything about what the camera will do with the highlights, which is mostly where the problems (at least they do for me in LA in the sunshine) arise.

OTOH, I just woke up and the caffeine has just started circulating. What I don't get is how incident readings can be matched against reflected readings except at one particular chosen subject reflectance.

[Keith_Strickland]

Hey Kevin
Seems to me that your question has been answered..the other posters question re highlights can be solved by using a tricolor card,white,gray,black and matching the spikes of your camera/s histogram to your meter,also there is the system of facial histograms for portraiture.
We also have a real professional photographer saying he doesnt need meters for exposing or for setting lighting ratios..that is all well and good for someone who obviously knows his craft,but we are not all at his level and you would be a fool just using your histo if you didnt understand how to expose or light for wrap around lighting of faces,you do need a meter for that and also for setting up your lighting system for consistent results which is what studio photography is all about.Unless the vast majority of pro photographers and film makers who use meters are wrong of course.. [img]/ubbthreads/images/graemlins/grin.gif[/img]

[Bern_Caughey]

In perfect conditions with a perfect lens you could calibrate your incident meter to your camera's ISO. These perfect conditions would involve flat lighting a medium reflective subject & background, but outside of these conditions you'll likely need to make some adjustments. Shooting against strong backlight or with specular light against a white wall & you'll need to close down from the meter due to flare. Shooting in really low light you may need to open up due to lack of reflectance.

Additionally all f-stops are equal in the real world. The following quote is from ASC's American Cinematographer Manual.

"The "T" stop number is defined as being the true "f" stop.
...The T-stop can be considered as the "effective" f-stop.

...T-stops are calibrated by measuring the light intensity electronically at the focal plane, whereas f-stops are calculated geometrically.

...The difference represents light losses within the elements of a given lens due to reflection from the glass-air surfaces and from absorption within the glass itself.

...A zoom lens..., will transmit considerably less light than a conventional fixed focal length lens of similar ratings with fewer elements."

When using the camera's TTL meter you don't need to compensate for light loss, flare & some other variables. But an incident meter can still be very handy with complicated lighting or when "lighting air" or when using strobe. At various times I use an incident meter or the TTL meter or a combination of both. I even throw in some external spot metering when need be. The camera's histrogram can be useful, but often is indecipherable. What's a good histro of a woman in white against a white cyc look like?

Digital capture has changed many things but the fundamentals of photography remain the same & there are still no easy answers. What works for one photographer can be completely wrong for the next & only you can tell which tools fit your needs.

Regards,
Bern Caughey