Sync Speed? How do I know what's right?

Gilly B

Gilly B

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Gillian
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I have been really dumb and only just found out that the sync speed on my studio set up has been all wrong. It went something like this:-

Purchased Portaflash studio kit as well as a Sekonic L308B flashmeter from Jessops when I owned a 20D & 350D. Got home, set it all up and read the instructions and it said set the flashmeter to your camera's sync speed. Doh! what's that:thinking: Couldn't find it under sync in the manual - so I rang the highly trained personnel at Jessops :geek: and asked them what is the sync speed of my camera to use with the flashmeter. The guy confidently said 60. Ever since, and on my 350D and my new 5D I have been using 60. Now whenever I used the flashmeter with ISO100 and 60 speed, it then gave me an f number to set my camera up which was supposed to be the correct exposure. It never was or has been correct and therefore I have not used the flashmeter. I just fiddle around with the aperture until something looks okay and finish it off in PS.

I have just had an interesting conversation about portraits and lighting techniques with a guy at our camera club's AGM. I said I am self taught and unhappy with the results I am getting in the studio etc. When he asked me if I use a flashmeter and I then told him the tale of woe, he nearly choked when I said 60, that should be 250 or at least 125 and it may be different on each of the cameras. Oops!

After I arrived home and checked both instruction manuals, I did indeed find the sync speeds were 125 and 250. However, it does say try these and adjust until the sync speed is correct. Phew! that was long winded, but the question I would like to ask is:- How do I know what or when I have achieved the correct sync speed? What happens to let me know that I have the correct one:shrug:

Please help me and apologies for those who have already got bored in reading this and probably fallen asleep. :lol:
 
My experience of the flash meter set thing is that
1/ you need a higher ISO then you think - so that you can use the lower power of your lights effectively
2/ changing the f-stop has little effect -practically once you have set sync speed on your camera and ISO.
3/ for basic - infocus well exposed shots (not fancy styles) f8-f11 + Iso200 with your lights should be agood starting point.
4/ Finally - test shots at differant light power settings are the most reliable way of building a repeatable methodology in a short time.
5/ Finally again - If you get a complete frame your sync speed is within the operating speed of your light/camera set up. Thats how you know its OK. Faster helps with handheld stuff or moving subject (if you want to freeze it) but basically as long as your camera sync speed is faster than your lights it'll be good.
If any of this latenight gobble-de-gook is patent rubbish I am sure someone will put it right just for the hell of it. Regards.
 
Gilly, I have to write the 2nd part of my SLR article which will deal with focal plane shutters and flash sync speeds when I get round to it.

The only reason your camera has a flash sync speed at all is that in common with all SLRs it has a focal plane shutter. In order for you to be able to look through the lens to compose your shots in the viewfinder, they had to remove the shutter from it's traditional place in the lens and move it to the back of the camera where it sits right in front of the sensor - almost touching it in fact. That's why it's called a focal plane shutter it sits (as near as damn it) in the plane occupied by the sensor.

A focal plane shutter consists of two metal blinds which travel vertically upwards in front of the sensor. The first blind travels upwards, exposing the sensor for the desired exposure time, then the second curtain closes (travels upwards) when the exposure is complete, covering the sensor again. When the camera resets the shutter, the second blind hooks onto the first and both blinds are wound back together so that the shutter is ready to fire again and repeat the process.

There's a limit to how fast those blinds can move across the sensor and unlike traditional shutter mechanisms they take a serious battering with continued use which is why focal plane shutters have an anticipated life in terms of the numbers of actuations.

The downside as far as flash is concerned is that the flash needs to fire when the first curtain has completed it's travel exposing the sensor, and before the 2nd curtain starts to cover the sensor. The limit with your camera is 1/250th second. At faster speeds than that the shutter achieves it's speeds by the two curtains travelling together, but leaving a slit between them to expose the sensor incrementally as the slit travels upwards. The faster the shutter speed - the narrower the slit. Obviously if you fired the flash at one of these faster shutter speeds the only part of your scene which would be lit by the flash would be a narrow band corresponding with where that slit was when the flash fired.

Your camera has a max flash sync speed of 1/250th second but it will also sync at any slower shutter speed as obviously the whole sensor will be exposed when the flash fires. I don't see where 1/125th comes into it at all apart from being a usable sync speed like all the other slower ones.

I hope that helps some for now. I will get round to that full article. :)
 
You're mate was right about it being different on most cameras. My effing Minolta won't sync any faster than 1/200 without engagin HSS (not a studio thing so don't worry about it). Add a radio trigger and it won't sync faster than 1/125.

You'll know when your sync speed is too fast because you will get a black line across the top or bottom of the frame depending on which way you curtain travels.
 
Great explanation there from CT - didn't know why there was a 1st and 2nd curtain until now - thanks for that:thumbs:

Gilly - 60 has been the default shutter speed for all my cameras with either flashguns - i can manually adjust up to 250 as necessary (or indeed strobe - which now makes sense from CT's shutter explanation ;)). So. I guess your Jessops Monkey was fairly close and certainly nothing to worry about
 
Focal plane shutters initially had pretty crappy sync speeds around 1/60th. Originally they all travelled horizontally but when they changed the travel to vertical obviously things got a bit quicker because of the shorter travel.

Kudos to Nikon though... some of their cameras flash sync at 1/500th which is an enormous advantage for sports/action togs wanting to use fill flash. :notworthy:
 
LOL. Credit where it's due. :lol:
 
That moving slit btw at high shutter speeds has been responsible for weird distortion effects where a feature of the moving subject has by pure fluke coincided with the slit throughout it's travel . A galloping horse with an elongated head is a famous one with a horiziontally travelling shutter.

This is a very famous one where the shutter was travelling vertically and the photographer was panning to the right.
lartigue.jpg


Thankfully these freaks are rare although there are people who deliberately exploit the effect .... 'slit photographers'. Jonny! :rules: Janice! :nono:
 
:whistling:

Doh - too many options!!!!!!!!!!!! :bang: :bang: :bang:
 
What a cool topic I hav learnt something new today, nice 1 CT :clap:
 
nuffink said:
What a cool topic I hav learnt something new today, nice 1 CT :clap:
Click to expand...

That's great and thank you - makes it all worthwhile.:)

One of the nice things about old film SLRs is you can take the back off, and fire the shutter at different shutter speeds to see how it works. You can't take the back off your DSLR but you can take the lens off and fire the shutter at some nice slow speeds to get a handle on what's happening. Keep the camera upright and you wont get any dust in there.

Understanding how the FP shutter works goes a long way to sorting out the problems people have with flash sync.
 
Just to add my 5 pence worth.....

In a studio you do have have control over the lighting and most studio heads have modelling lights... (tungsten usually). The faster the sync you can use the less the effect of any ambient lighting. Conversely, if you use a slower shutter speed then any ambient light can nullify any modelling from the flash heads. This is the reason you should set the the meter to the sync speed you will be using, (not all flash meters are this clever) that way you account for the exposure effects of any ambient lighting AS WELL AS the flash....

Thinking about that statement, it's pretty much true for any use of a flashgun/flash setup! ;)
 
See I was right. Hee Hee! CT put it all techy for you - Great stuff. However the ambient light thing is useful to remember if you use you studio set up in different locations (non studio). Like under the bright orange lights of a warehouse or sports hall. For getting the shot 'fast is good'.
 
Joe T said:
Cheers CT (and others). :)
Click to expand...

It's me who needs to thank CT, Sharkey & others for their useful comments. I have only just got in and seen the responses.

It is good to know that until you post a query like this, you just don't know how many other people might benefit from it, and for that reason too - I am glad I did.

Just to re-cap then. 60 is not unacceptable then? So I set the ISO on the flashmeter and my camera to 200 then? and then set the speed for 60, 125 or 250 and see which one does not show a black banding. (doesn't at 60).

My only concern is that everyone talks about getting the one flash head pointing to the background and the other at the front to be used as a key light. Understand all that. What I don't understand is that I have read that you need to up the background light to between 1 and 2 stops to blow it out? I have the portaflash system and the light settings are either 1/4, 1/2 and full power, does anyone know in relation to f stops, what these fractions mean?

I am sorry to keep harping on about it, but I need to get it right and also improve my performance as a photographer. Thanks:thumbs:
 
just turn the light up or down till when you test it with the flashmeter it reads two stops brighter than the subject.
 
Hi Janice - thanks for that. Let me see if my brain took that one in....

Take a reading off the subject's face pointing towards the camera and assume the reading is ISO200 shutter speed 125 and f stop is f8 - do you then go to an area close to the background and take a reading off that pointing to the camera. Should I expect the f number to read f 9 or f11? or f7 or f5.6?

Oh dear, I am in danger of losing the plot here.:cuckoo: :bang:
 
If you want to have full control of the lighting you really need to get rid of all possibility of your exposure being influenced by any other ambient room light or window light. The duration of electronic flash is incredibly brief probably around 1/500,000th of a second, although it can vary either way. What that means is that regardless of how fast a shutter speed you use, the flash has fired and died long before that second curtain starts to close, so the sensor is still exposed to being influenced by any ambient light - which may be bright enough to spoil your carefully arranged lighting.

For that reason it's probably best to use the fastest shutter speed you can - 1/250th.
 
Gilly B said:
Hi Janice - thanks for that. Let me see if my brain took that one in....

Take a reading off the subject's face pointing towards the camera and assume the reading is ISO200 shutter speed 125 and f stop is f8 - do you then go to an area close to the background and take a reading off that pointing to the camera. Should I expect the f number to read f 9 or f11? or f7 or f5.6?

Oh dear, I am in danger of losing the plot here.:cuckoo: :bang:
Click to expand...

the reading isnt actualy going to tell you all that info. you would already have put in the iso that your camera is using, and teh shutterspeed that your camera is using. put the meter at the subjects face with the dome sticking up (if thats the type you have) and flash your main flash (joined to the meter by a sync cord) and it will tell you what Fstop to use.

then you measure the light which you have on the backdrop by joining the flashmeter to that flashunit. if the face read F8 then the background should read about F16 unless my mind has gone and its late.......but I know what I mean. jsut alter the flash power till it works. :D
 
What Janice said Gilly - you choose the ISO before you start. :)
 
OK. What is Gilly going to photograph? What style is wanted? Give me a clue and I will try and do a brief simple method. Not techy but workable and confidence boosting. I hope.
 
Good man Sharkey - practical help! :thumbs:
 
I think, like me, she wasnts a subject in front of a blown out white background.

Id like to know how to make sure we dont get light bouncing off this back onto the subject too!
 
In the days of film this was pretty cutting edge because the darkroom capabilities meant that light bleeding into the suject was a definite no no. With digital the set up is easier to police. So lets give it a go.
 
Thank you, although I might not answer till the morning cos Ive got to go to bed now!! :baby:
 
I assume you have some control over your lightin power output. So what do you need? Ideally (4)four lights but (2) will work for single, small subjects.
1/ Two lights - Camera set to ITS synch speed (the lights will almost certainly be faster) so no probs there and choose ISO (prob 200).
2/ For simple portrait (head) put main light in front of subject slightly above eye level and offset by about 20degrees. Set light power to middle of range and then hold your meter (also set to ISO 200 and camera sync speed) towards the light on the models forehead. Fire the light (one only).
I would expect f11-f8, above that is too high - so move the light away, slightly and retry. Hopefully you now have an exposure of f8 ish.
3/ My method for the backlight would now be to place it behind the subject pointing at the backclotha such a level that it cannot be seen by the camers ie, low down. With model out of the way and the first light off set the second light ot the mid power setting again and take meter reading from that light on the backcloth - look for f8 again. Dont panic all will become clear.
4/ Now still with no model fire both lights and take a reading from the two already mentioned positions - first where the models face would be and second from the backclothe behind the models head.

You should find that the models face is still f8 and the backcloth has risen by approx one stop to f11.

Reploace model for final check (take your time)

Face f8 - clothe f11 great a one stop differential
Face f8 - clothe f16 not great, will cause light to bleed into subjects face.

Solution - move backlight slightly away from cloth and re -meter
lower backlight power if possible or place scrim (whiteclothe) between light and backclothe (soft box if you have it for both lights will help)
 
Good morning everyone. Apologies for not staying up to see any responses. In fact, I fell asleep typing the last query to Janice :lol:

Sharkey - that sounds easy enough to set up. I am going to give it a go later today. I have a baby portrait to do tomorrow. I use a White background just as Janice mentioned.

I always pick up methods and techniques if I am told exactly what to do and what results to expect. I will print this thread out and take it with me when I set the lighting up. I can't help being a bit thick :cuckoo: :lol:
 
Thanks for that Sharkey, Ive only just remembered I went to bed the other night and forgot to read it in the morning!! :cuckoo:

Like Gilly, this is exactly what I need to read and I can actually understand it!

Thank you! :thumbs:
 
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