Confused about custom white balance

[tirediron]

Now, to get back to the issue at hand: Each light in a setup serves a specific purpose. Start with your key or main light. That is the light which will provide the bulk of the illumination for the set and the one on which the exposure is based.
One thing we can't tell is how far your product is from the background; you want as much separation as possible, and you should probably raise the height of the seamless as well.


Let's start with the key. Use #4 (I am going to pretend that these are your new strobes), and position it so that it is about 30 degrees camera right and angled about 45 degrees down. Place it so that the closest point of the front is no more than 2' from the product and adjust for f8. Bring in #3 just a little bit off-axis camera left (maybe 10 degrees) and angled only slightly down off of the vertical. Get this as close as you can as well; ideally within 2' and set for f5.6. Position 1 and 2 so that they cross light the background (ie the light on the right side of the table illuminates the left side of the set) and so that they are roughly even with the product. Set them to f8.

You're now in the ballpark... roughly. Shoot a test shot and tweak the positions of the lights slightly as necessary to eliminate any excess specularity. Using the stock of white & black card to flag & reflect, tweak small areas until you have it dialed in. For products that are very highly polished you may need to employ cross-polarization (a cut of polarizing film on the light and a CPOL on the lens).

 

[Quovadis]

Thank you both ...now I can start working on something tangible.
I was making the first fundamental mistake of backing my lights further back trying not to get reflections. I understand I need to move them closer. I will also raise the backdrop. The subject, was too close to the background, yet another mistake.
Another mistake is to try and use brute force and have all lights as fill.
I do not understand how to set a light at f8? You mean using a light meter? I do not have one. The strobes I am about to receive only have a rotary knob on the back to go from full power down to less power.

 

[tirediron]

Thank you both ...now I can start working on something tangible.
I was making the first fundamental mistake of backing my lights further back trying not to get reflections. I understand I need to move them closer. I will also raise the backdrop. The subject, was too close to the background, yet another mistake.
Another mistake is to try and use brute force and have all lights as fill.
I do not understand how to set a light at f8? You mean using a light meter? I do not have one. The strobes I am about to receive only have a rotary knob on the back to go from full power down to less power.

You really should have a flash meter for this; it will make your life much, much easier! Failing that, you can use the guide number to do a rough calculation and then fine tune using the rear LCD, or just take a wild-ass guess, and then adjust the power, review, adjust, etc....

 

[table1349]

Excellent meter at a decent price. L358

This is what I use. There are many others of varying prices. Sekonic has a good number of tutorials on meter usage.

 

[tirediron]

Excellent meter at a decent price. L358

This is what I use. There are many others of varying prices. Sekonic has a good number of tutorials on meter usage.

I love my Minolta Flash V!

 

[Quovadis]

Gosh
I know nothing about light meters, if my understanding is correct, I measure ambient light where the subject is, and the light meter will tell me an f aperture number to use on my camera? I do not think my strobes will have an LCD screen. They are basic strobes, with a knob.
Here is the model, I ordered four pieces with light box.
https://www.amazon.com/NEEWER-Studi...625371&sr=8-1&keywords=neewer+250+watt+strobe

 

[Quovadis]

let's say my light meter says f8, then what? The knob does not have F values just clockwise and anti clockwise rotation.

 

[tirediron]

You don't care about ambient; this will be 100% flash exposure, which is why you need a flash meter, NOT just a regular light meter. Set up your strobe, place the meter where the product is, trigger the strobe, and look at the meter; it will give you an aperture reading. Adjust the output of the strobe up or down until you achieve the desired reading.

 

[unpopular]

Meh. Just get a polarizer.

 

[tirediron]

let's say my light meter says f8, then what? The knob does not have F values just clockwise and anti clockwise rotation.

If let's say you trigger the strobe and your meter shows f11, but you want f8, simply reduce the output of the strobe by turning the dial (usually counter-clockwise). Some strobes are marked in stops and fractional stops, others it's just a guess. By the time you've had them a day, you will know instinctively how much to turn the dial to achieve how much increase or decrease.

 

[Quovadis]

You don't care about ambient; this will be 100% flash exposure, which is why you need a flash meter, NOT just a regular light meter. Set up your strobe, place the meter where the product is, trigger the strobe, and look at the meter; it will give you an aperture reading. Adjust the output of the strobe up or down until you achieve the desired reading.

Ah!! ok so this is a specific flash meter.
Ok let me take this step by step :

1. Approach the subject with a hand held light meter, and hold the meter right close to the subject.
2. Trigger the strobes? How? My camera has to trigger the strobes wirelessly ? Right? My camera is not here where the subject is.
3. Assume the strobes are triggered and the flash meter says f8 for example.
Then what? How do i tell the strobes I need f8?
I only have full power or reduced power on the strobes...how do I set f8?

Why do they measure strobe light intensity with aperture numbers? can't they just say 1= dim and 10= strong? It's really confusing..not logical

 

[Quovadis]

yes but the meter reads the intensity of the flash? How does the meter know what is needed?
Let's say I dim my strobes to the lowest possible point with the rotary knob. I then take a reading with the flash meter, the meter will simply give me an F number.
Let's say i take another reading with the knob on the strobes turned on maximum, the flash meter will give me another f number?
So i end up with two F****numbers? how do i use these in practice?

 

[tirediron]

It's actually very logical because f8 is an absolute value and is f8 is f8 is f8 no matter what camera you're using. "Dim" or "Bright" are relative terms and will not tell you what you need to know.

Okay... baby steps.

First decide what aperture you want. This will be determined by the depth of field necessary to have the amount of the scene in sharp focus that you want in sharp focus. The DoF is determined by the focal length of the lens, the aperture and the distance from the subject. You know the focal length and distance because you've figured out where you need the camera to frame the image the way you want. Now, take those two parameters and consult your DoF table of smartphone "app". It will tell you what aperture you need. For the sake of example, you need f8.

Now, set up your strobes the way you want, and make a WAG about the power settings; failing all else, go for the middle on all of them to start. Now, take the trigger off of your camera and place the meter against the subject, and using the test button on the trigger, trip the strobe FOR YOU KEY LIGHT ONLY (turn the others off for now). Let's say that the meter now shows f11. Reduce the strobe output power by a bit and test again, repeat until you have f8.

Next turn off the key light and turn on the fill light. You've decided that you want 1 stop of dynamic range between highlights and shadows in the shot, so that means you will need to set your strobe to f11. Repeat the 'test-adjust-test-adjust' process with your fill until you get f11.

Once the fill is done, turn it off and turn on both background lights and meter the background AT THE BACKGROUND; you want f8 (same as your key) or slightly above, say f8 +1/3; just enough to render the background pure white. Once you've done that, turn on all the lights, place your trigger back on the camera's hot shoe and shoot the scene with the camera at f8 and maximum sync speed (usually 1/200 - /250) and look at the image you get. Start adding flags and reflectors as necessary to increase or decrease light to a specific area.

 

[Quovadis]

OK ..let me rephrase my thinking :
We have 3 variables a camera which needs to shoot bags at f11.
A flash meter which records the intensity of a given light or flash (f numbers),
and 4 strobe lights with an adjustment knob.
The flash meter can only record a flash if the strobes are triggered. Once the strobes are triggered it will give me an F number.
Let's assume it reads f14.
I need f11 because i'm shooting at f11.
We have a discrepancy of 3. So the lights have to be increased or dimmed by 3? Not sure. I think dimmed.
So i have to dim the all 4 strobes by three points/stops/intensity ?
Is this correct?

 

[table1349]

Gosh
I know nothing about light meters, if my understanding is correct, I measure ambient light where the subject is, and the light meter will tell me an f aperture number to use on my camera? I do not think my strobes will have an LCD screen. They are basic strobes, with a knob.
Here is the model, I ordered four pieces with light box.
https://www.amazon.com/NEEWER-Studi...625371&sr=8-1&keywords=neewer+250+watt+strobe

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