Speed lights, light meters do i need?

grahamricho

Active Member
Hi all.
I build lightboxes basically a box with led lights in and a opal perspex front and want to take some high quality photos of them out up.

I recently bought a new fuji xt30 camera with the kit lens and a godox speedlight.

I'm still experimenting with the set up.

I started looking at videos on youtube and a few used light meters to get a perfect exposure.

My questions are would a light meter help?

What I can not get my head around is after watching people use light meters is you put the preferred ISO in and shutter speed and it tells you what the aperture
should be? But if you want a creamy back ground you want a low number aperture say f2.8 it would be pointless using the light meter? Or am I missing something?

Also if using a flash and a light meter how do you hold light meter near subject and initiate the flash to get a meter reading ?

Thanks
 

snerkler

Member
Hi all.
I build lightboxes basically a box with led lights in and a opal perspex front and want to take some high quality photos of them out up.

I recently bought a new fuji xt30 camera with the kit lens and a godox speedlight.

I'm still experimenting with the set up.

I started looking at videos on youtube and a few used light meters to get a perfect exposure.

My questions are would a light meter help?

What I can not get my head around is after watching people use light meters is you put the preferred ISO in and shutter speed and it tells you what the aperture
should be? But if you want a creamy back ground you want a low number aperture say f2.8 it would be pointless using the light meter? Or am I missing something?

Also if using a flash and a light meter how do you hold light meter near subject and initiate the flash to get a meter reading ?

Thanks
Light meters can help, but they're not essential.

With regards to using flash and/or studio lights, assuming that you are not using HSS then shutter speed does not influence the amount of light from the flash, and light is controlled by the power of the flash output, aperture and ISO. The larger the flash output, the larger the aperture (smaller f number) and the higher the ISO the higher the exposure and vice versa.

So back to the light meter I'm not sure why they're talking about shutter speed tbh. It's a long time since I used a light meter, but from memory I think you can put if ISO and aperture and it gives you the flash power, or some combination of that.

There's also a couple of ways that you can do it without a light meter. First is TTL, this way the flash automatically determines how much power to put out for the given scene and camera settings. This is by far the quickest and easiest and generally you get good results, you can even tweak it by using flash exposure compensation.

However, if you want to replicate the exact exposure time after time then it's best to use manual exposure and manual flash. Without a light meter you can just use trial end error. Set up your camera, for example f2.8, iso 200, 1/200 shutter. Set the flash to 1/8 (or whatever you choose), review the image (preferably via the histogram) and alter the flash settings as necessary to get the exposure you want. Once you have this remember it for next time and assuming nothing else has changed (such as the brightness of the room) your exposures should be consistent.
 

grahamricho

Active Member
After further reading up on the sekonic 308 light meter it seems you put in the desired ISO and then take the reading and it tells you the shutter speed and aperture settings. Then if you want to change the aperture it automatically displays the correct shutter speed
 

12harry

Distinguished Member
Hi, am I understanding you are photographing the Light-boxes you are selling?
Modern cameras are very forgiving about exposure, but if the idea is to underexpose to show how even the lighting is... the easiest thing to do is to alter the cameras exposure. Somewhere in the menu there will be an exposure scale that allows a stop or two either side of "normal" - which is for a "typical scene" - despite mfrs claims there isn't yet an intelligence that knows what result you want = beforehand.
There are Neutral Density filters that can range over several stops - but perhaps you can explain the problem better when you've taken a couple of dozen shots ( noting all settings carefully!), and report back.

FWIW
I'd avoid flash unless the position is fixed - it can be quite "variable" and difficult to control if hand-held . . . .also, the shadows it creates are less than flattering.
Have you considered the background? - will it be out-of-focus, to make your box nice and sharp?

Cheers
 

grahamricho

Active Member
Hi thanks the background will be a brick wall which the lightboxes which I'm selling will be hung on before I take the photos
 

grahamricho

Active Member
Yes a blurry background would be good but the boxes will be attached to the wall so it may be hard to achieve since no depth behind the boxes?
 

snerkler

Member
Hi, am I understanding you are photographing the Light-boxes you are selling?
Modern cameras are very forgiving about exposure, but if the idea is to underexpose to show how even the lighting is... the easiest thing to do is to alter the cameras exposure. Somewhere in the menu there will be an exposure scale that allows a stop or two either side of "normal" - which is for a "typical scene" - despite mfrs claims there isn't yet an intelligence that knows what result you want = beforehand.{/quote]
I'm assuming you're referring to the camera's light meter which shows the 'correct' exposure, in which case these are usually displayed by default. You are correct in that a camera and/or flash doesn't know what exposure 'you' want, but they do expose the scene 'correctly' in terms of achieving neutral grey, assuming you've metered correctly of course.

There are Neutral Density filters that can range over several stops - but perhaps you can explain the problem better when you've taken a couple of dozen shots ( noting all settings carefully!), and report back.

I'm not sure why you've recommend ND filters for this? All this will do is require more flash power or higher ISO, neither of which are desirable.

I'd avoid flash unless the position is fixed - it can be quite "variable" and difficult to control if hand-held . . . .also, the shadows it creates are less than flattering.
Have you considered the background? - will it be out-of-focus, to make your box nice and sharp?

Cheers
I'd disagree with this. There is a reason that most studio work use flash, and that is so that you have exact control of the light and shadows. This also allows consistent results time after time, and also more often than not gives more sharpness and detail.
 

snerkler

Member
Yes a blurry background would be good but the boxes will be attached to the wall so it may be hard to achieve since no depth behind the boxes?
If you're shooting against a wall then no you're not going to get blurry backgrounds, in which case I'd suggest stopping down to around f8, this way you will be able to show the best detail and sharpness.

In terms of the light meter showing shutter speed I can only assume that it's because they are balancing ambient light, if you're using flash as your main light source then up to your camera's flash sync shutter speed the shutter speed won't make a difference. I get frustrated my memory's so bad. I made some notes when I went on flash/studio courses, I'll see if I can dig them out later. I don't use a light meter as I don't use flash that much and for the time that I do I use the 'trial and error' technique I mentioned earlier, ie set a flash power and if it's too bright/dark adjust accordingly. If I was doing it more regularly or professionally I'd use a light meter.

With regards to using the flash, don't use direct flash as this will give very unflattering results and will result in a lot of reflections. If you want to do it cheaply initially then I'd suggest using bounce flash as this gives much better results. Another relatively simple cheap way is to use an off camera softbox and reflector.

This is using a single softbox and reflector on the other side pretty close to the subject

PA243435
by TDG-77, on Flickr

This is using a single softbox moving the reflector further away from the subject

PA243484-Edit
by TDG-77, on Flickr

This is using a single source of camera focussed light source
DSC_8734-Edit-2 by TDG-77, on Flickr
 

snerkler

Member
@grahamricho I know you're not doing portraits but the principles the same, maybe these will help?


bd36cd3161b9e1d714e43b763a9d6c82.jpg
 

grahamricho

Active Member
Thanks I do have a godox transmitter and godox speed light plus a stand and softbox. With so many things and adjustments its knowing where to start?

I may as you said start with f8 which is supposed to be my camera lens sweet spot. Then experiment with the flash.
Should TTL flash be better than manual?
 

snerkler

Member
Thanks I do have a godox transmitter and godox speed light plus a stand and softbox. With so many things and adjustments its knowing where to start?

I may as you said start with f8 which is supposed to be my camera lens sweet spot. Then experiment with the flash.
Should TTL flash be better than manual?
Manual is always better in a controlled environment imo, this way you have consistent reproducible results. TTL most of the time will give good results but there are certain things that will influence it and it ‘might’ not give the results that you want. Of course you can always use the flash compensation if this is the case.

I tend to reserve TTL for times when I’m not spending the time ‘setting the scene up’ or in a scenario where things are constantly changing.

Something to remember is the distance between your flash and subject will absolutely make a difference, not only as to how much light there is but the spread of light. If using a softbox the closer it is to the subject the more even the light tends to be, this is why when I shoot the softbox is only just off the frame of the camera. I want the light to be as soft as possible.
 

snerkler

Member
@grahamricho OK so lightmeters. You are right, you set the shutter speed, ISO, set the strobe/flash and then the light meter will tell you the aperture that you need for a given light (remember aperture is one of the factors that controls the amount of light). The shutter speed is slightly irrelevant as it will be at your camera’s flash sync speed (usually 1/200 or 1/250).

You can use your knowledge of stops then to adjust the flash power so that you get your chosen aperture. For example, lets say you did the above and the light meter says you need to be at f4 but you want to be at f8. F4 to f8 is two stops so you just increase the flash power by two stops.

I do think that there are some light meter and/or strobe combos that let you dial in what you need though so you can dial in the aperture etc and it will tell you what flash/strobe power you need to have it set to.

In essence having a light meter isn’t that much different to the ‘trial and error’ method I mentioned earlier, ie set your parameters then adjust as needed according to the histogram/your desired results.
 

Faldrax

Well-known Member
One advantage of a lightmeter is when you start to use multiple lights, where the lightmeter allows you to easily set / calculate the desired values of each independently.
EG You want a pure white background and a fill at 1 stop below key.
You set up the key, and determine the aperture required (shutter is based on sync speed).
This then allows you to independently set the background lights (which need to be a few stops above the key to just blow the background), and fill; using a light meter to do thsi with each in turn will get you to a good starting point much quicker than taking multiple shots in camera.

For what you are looking at doing, using a single light (you may well want to get a reflector as well, they're cheap and effective at providing fill, which can make a big improvement to shots), then a lightmeter is probably an added complication.

Set the camera on manual (base ISO, shutter 1/160, aperture f/8) , flash on manual (1/4 power), and adjust flash power and aperture to get the exposure you want.
Note: The reason for not using the flash on full power is that it will recycle quicker, up the power if you need to, just be aware you may have to wait 1-2s between shots.
 

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