Help with white balance please

Trev4

Trev4

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Trev
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I am attempting to take some product pictures to help a friend out (actually its a charity that my wife is a founder member of). My usual interest is wildlife photography so this is rather new to me.
I have set up a table with a white background, 2 speedlights (1 either side looking down and set to ETTL), a 430 and a 600 shooting through white umbrellas, triggered by the wireless function on a 7D.
The camera set to custom WB using a Lastolite grey/white card.
Shooting in RAW, evaluative metering, manual, ISO 100 1/250 f/2.8
I have tried spot metering, partial metering etc. but the results are broadly the same in each setting.

Imported through tethering straight to Lightroom. In PP I have applied exactly the same processes to each shot, these being setting the WB using the dropper and a small crop as necessary.

What I cant understand, through either ignorance, oversight, or what ever, is that each image has different levels of white on the BG. To my simple mind, with everything set the same for each shot, I should expect to see more or less the same results each time. Even though I have applied WB correction in LR, the differences are as noticeable as in the original RAW image.

I have attached a couple of examples here. I know they need a bit more refining, but I wanted to show them here before I messed with anything else to see if you could offer any advice please, and point me to where I am going wrong, or what I am misunderstanding.

It seems that the darker the item is, the whiter the BG, so some metering is going on that I thought I had set to manual.

This is my first time of using this type of set up so am very much a novice using flash etc.


knitting 22.11.14-034 by Trev4 Photography, on Flickr

knitting 22.11.14-031 by Trev4 Photography, on Flickr

Thanks for looking and I hope I don't look to ignorant and stupid when I am told where I am going wrong.
 
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mike weeks said:
You need to set your flashguns to manual, meter and set the exposure. Ettl is doing what it should do i.e. trying to make the whole image an average tone.

Mike
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Thank you Mike, that makes sense now you've pointed it out. Its a new ball game to me so I better read up about using them on manual. Cheers for replying.
 
A small tip:
It's exposure you're looking to correct, white balance is something else entirely. :D

So when you get the manual out, it's Manual flash exposure you're looking for.
 
Phil V said:
A small tip:
It's exposure you're looking to correct, white balance is something else entirely. :D

So when you get the manual out, it's Manual flash exposure you're looking for.
Click to expand...


Thank you Phil, I think that just about shows my knowledge of flash, I can understand why I was confused now that its been explained, you've all pointed my in the right direction.
I've only used flash on the rare occasion so have never studied it in detail. I've volunteered to do these pictures for the charity every month which is why I bought the umbrellas etc. its hopefully a help for them and will teach me more as I go on.

Its starting to fall into place now, but a lot more studying needed. I've got the speedlights into manual, in fact, both are now at their minimum output and I've taken the aperture down to f/18 to get the exposure right, I might play with the iso to use a larger aperture. Apart from getting the exposure correct and the colours right, I do have consistency in the exposures which is what I couldn't work out, so that's a great start to work from and I can learn from here.

Thanks very much everyone, its appreciated (y)
 
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mike weeks said:
moving the falshes further away will also reduce their power ;)

Mike
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Minimum ISO for that kind of flash work (I'll guess your ISO was high because you started by metering the ambient).

You can reduce flash power by moving the flashes as Mike says, but it also changes the effect of the umbrellas.

Other tips that might be pertinent, we use umbrellas to create larger light sources, which softens shadows. That's great for softening skin blemishes etc, but you're shooting knitted garments, so presumably you want to show the texture, which requires different lighting altogether.
 
At the moment I am still on ISO 100 Phil, 1/200, f/18. The whites are just starting to go very slightly grey, and the colours are broadly right (but not correct yet), so I'm thinking the settings are close and since following the advice on here I have consistency, just some fine tuning needed.

Your right, more or less all the photographs will be of knitted or occasionally sewn garments, so yes, the texture is important. May I ask you what you would suggest please. because of the nature of the work, and as I will only be using the lighting for this project, I cant justify buying expensive specialised kit so hopefully I can work around using speedlights.
 
To create visible shadows, you want a harsh light to cross the surface, if you put it too close there'll be too much contrast between the nearest and furthest point, so with a flashgun, try about 6 feet and if you can fashion some kind of grid to help keep the edge of shadows crisp.

When that looks ok, put your fill light, large and soft at the camera position, to light your subject but not to overpower the first light.

Oh, and set the white balance to flash.
 
That sounds sound advice, thank you Phil and Mike. I can understand (I think) the principle that you are suggesting. I've Googled grids to see how they are made, I'll have a go putting it practice now. Thanks again for taking the time to reply.
 
Trev4 said:
That sounds sound advice, thank you Phil and Mike. I can understand (I think) the principle that you are suggesting. I've Googled grids to see how they are made, I'll have a go putting it practice now. Thanks again for taking the time to reply.
Click to expand...
I've seen diy solutions for speedlights made with black straws, iirc there is a range of speedlight modifiers that includes a grid for sale.
 
I strongly suggest you buy a grey card. They are very cheap.

One side of the card is 18% grey and that's the side you can use to check exposure. The reverse of the card will be a very light grey and you use this for white balance.

Your camera manual will explain how to set a custom white balance and there are countless videos on Youtube.

At the start of your shoot, measure exposure and get that right first. Then take a shot of the white balance side of the card which you can then use in Adobe ACR to correct the while balance.

You may want to look into the use of the Colourchecker Passport (which actually includes a grey card and white balance card).

Set your shutter speed at your maximum flash sync speed, usually 1/200th or 1/250th of a second, depending on your camera. Decide what aperture you want to use for the depth of field, then adjust your light until you get a correct reading for that aperture.
 
Thanks a lot for taking the time to reply Jenny. I am doing all you suggested already, if you check my opening thread you will see that, but I still appreciate you replying. The problem was that I was using the flash's on ETTL and the camera on manual, now that I have changed everything to manual I am getting consistent results. Its something that I should have realised myself, but I rarely use flash as my main interest is wildlife and BIF, so have gained no useful experience with flash. The advice from the generous members on here pointed me in the right direction very quickly which helped to get the pictures that I needed out quickly.
Thanks again for your help.
 
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