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01-11-2018, 03:10 AM   #1
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To flash or not to flash?

I have recently purchased a used Sigma EF-610DGST flash thinking I could use it during the grey days of winter in my back garden. My K-5 syncs with the flash at 1/180th of a second so I set the ISO to 400 and the aperture to F8, put my DAL 55-300 to FL 300 and had a go. With the shutter speed without flash longer than 180th sec I was hoping the flash would isolate a crisp image with the flash duration (I expected this to be very short) and the image provided have the intended subject as good as it gets with no shake visible (hand held) or movement visible in the image.
Should I be looking to use settings that provide a much longer shutter speed, say 1 or more seconds to achieve better images? Or am I always going to find problems with the image?
I chose ISO 400 to give me plenty of range with the flash and have assumed that longer exposures would leave me with mostly just the illuminated image as provided by the light from the flash.
I really should be getting out and trying to determine it myself but am suffering with a post Christmas period of overindulgence of rich food so thought the forum would help and provide much better information than I might eventually garner when I am fit for more shooting.

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01-11-2018, 04:14 AM   #2
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Are you sure the flash fired at all (I guess so, given the shape and position of the shadows), or that it was firing at or near full power?
Dragging the shutter (i.e. using slower shutter speeds) will only help with ambient light, but do nothing to counteract blur.
01-11-2018, 04:28 AM - 1 Like   #3
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If you want to use the full power of the flash, then 1/180 of a second is the highest shutter speed you can use. You could use a faster shutter speed AND set the flash in HSS (High Speed Sync) mode BUT the power of the flash will be reduced, sometimes considerably.

The important question is "How far away was the bird you were focusing on?"

Flash power decreases with the square of the distance. If you have the right flash power for a subject 2m away you will only have a quarter (1/4) of that power if the subject is twice that distance (4m) away.

Using the Pentax AF-540FGZ flash as an example, this flash has a Guide Number of 54 (at ISO 100 and using metres). (The flash you quote probably has a Guide Number of 61 from the name EF-610DGST.) The guide number doubles to 108 at ISO 400 which you were using. The flashes effective range at maximum zoom and with f8 as the aperture (from your photo) is 13.5m. Effective Distance = Guide Number / Aperture. If your bird was twice that distance away at 27m you would only get a quarter of the flash's power. If your bird was three times that distance away at 40m you would only get a ninth of the flash's power.

To get more light on the subject you need to do one or more of the following:
1. To open up the aperture and let more light in.
2. Use a more powerful flash.
3. Use a snoot on the flash to concentrate the light better.
4. Get closer with the flash to the subject.
5. Use more than one flash.
6. Use a lens which is faster - has a larger aperture at the 300mm focal length you were using. Maybe a 300 f4 or a 300mm f2.8 lens.

Hope this helps.

Regards

Chris
01-11-2018, 04:51 AM   #4
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QuoteOriginally posted by seventhdr Quote
*snip*

The guide number doubles to 108 at ISO 400 which you were using. The flashes effective range at maximum zoom and with f8 as the aperture (from your photo) is 13.5m.

*snip*
For the Sigma:
61 * 2 = 122
122 / 8 = 15.25 m

Otherwise yeah.
https://www.sigmaphoto.com/ef-610-dg-st-flash

Given subject size, I don't think he could have been much further away... so check it was at max power... try manual mode in order to be sure, and also check max zoom (105mm setting), if it's not automated.

01-11-2018, 07:06 AM   #5
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The bird was about 10 to 11 metres away.
The flash was set to TTL (this flash works with PTTL) and the indicator showed the maximum 105mm FL. It should have exposed the bird correctly as this is auto mode.


Is my reasoning correct that the slower the shutter speed at an aperture the more the flash duration has effect?
If the shutter speed indicated without flash is 1 or more seconds, the sync speed using flash is 1/180th sec and the duration of the flash is in x/1000ths of a sec, should the only parts of the image illuminated by the flash at this faster flash duration show in the image and any movement be too underexposed to show? I remember taking multiple images of my wife in the dark with flash on film, donkeys years ago.


I could always try it out indoors until my tummy stops complaining I suppose, just wanted it to be tried at distance. I should also read up on high speed flash sync and the K-5 manual regarding flash.
01-11-2018, 07:19 AM   #6
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QuoteOriginally posted by Skodadriver Quote
Is my reasoning correct that the slower the shutter speed at an aperture the more the flash duration has effect?
If the shutter speed indicated without flash is 1 or more seconds, the sync speed using flash is 1/180th sec and the duration of the flash is in x/1000ths of a sec, should the only parts of the image illuminated by the flash at this faster flash duration show in the image and any movement be too underexposed to show? I remember taking multiple images of my wife in the dark with flash on film, donkeys years ago.
No.
Flash duration is very short and only depends on flash power (but is very short nonetheless).
Slowing shutter speed will change the contribution of ambient light, influencing the areas of your picture that aren't illuminated by (or get little light from) the flash.

For instance, let's pretend you shoot a flower at 2m, with a background at 20m. If you shoot at 1/180s you'll probably see the flower and the background will be all black. Dragging the shutter will allow you to get (available) light from the background as well, but won't affect how the subject is "frozen".

Zoom was ok, so my belief is that TTL gave enough power to expose the scene correctly, but much less than it was needed to freeze the subject. Since ambient light was plentiful, at ISO400 f/8 1/180s you were probably already close to a correct exposure, so the flash contribution was minimal.

Your options:
1. stop down more, so you reduce available light and the flash will increase its power
2. use a faster shutter speeed, thus reducing available light, and forcing the flash into HSS mode (if it's supported): you'll reduce maximum power, but flash contribution will be proportionally higher, and you won't need max power anyway at 10m
3. use option 1. but in manual mode, and ensure the flash fires near full power.
01-11-2018, 07:30 AM   #7
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P-TTL seems to favor a natural look and wants to reflect scene lighting. It has been my experience that manual flash is needed to get the type of result you were interested in. One quick and dirty way to get this is to use the X mode. There's a nice flash guide by a forum member that may help.
01-11-2018, 07:31 AM   #8
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QuoteOriginally posted by LensBeginner Quote
No.
Flash duration is very short and only depends on flash power (but is very short nonetheless).
Slowing shutter speed will change the contribution of ambient light, influencing the areas of your picture that aren't illuminated by (or get little light from) the flash.

For instance, let's pretend you shoot a flower at 2m, with a background at 20m. If you shoot at 1/180s you'll probably see the flower and the background will be all black. Dragging the shutter will allow you to get (available) light from the background as well, but won't affect how the subject is "frozen".

Zoom was ok, so my belief is that TTL gave enough power to expose the scene correctly, but much less than it was needed to freeze the subject. Since ambient light was plentiful, at ISO400 f/8 1/180s you were probably already close to a correct exposure, so the flash contribution was minimal.

Your options:
1. stop down more, so you reduce available light and the flash will increase its power
2. use a faster shutter speeed, thus reducing available light, and forcing the flash into HSS mode (if it's supported): you'll reduce maximum power, but flash contribution will be proportionally higher, and you won't need max power anyway at 10m
3. use option 1. but in manual mode, and ensure the flash fires near full power.


DOH! I should be increasing the shutter speed OF COURSE! I blame my wife's Christmas cake, she soaked the fruit in cheap Spanish brandy and my head hurts. My apologies and thanks to all.

---------- Post added 01-11-18 at 07:39 AM ----------

QuoteOriginally posted by UncleVanya Quote
P-TTL seems to favor a natural look and wants to reflect scene lighting. It has been my experience that manual flash is needed to get the type of result you were interested in. One quick and dirty way to get this is to use the X mode. There's a nice flash guide by a forum member that may help.
Thank you, I really need to find out where my K-5 manual is, my wife made me put it away somewhere safe when she tidied the house up before Christmas. I have not gotten round to reading up on flash and have recently bought 2 PTTL flashes, Pentax AF200FG that I'm hoping to attach a Pringles tube to for hand held macro and the Sigma for higher power stuff and two weddings this year.


Lensbeginner has kindly pointed out that making the shutter speed slower rather than faster has made me seem awfully stupid.




01-11-2018, 07:44 AM   #9
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These modern dslrs are complex and it's easy to forget the ways to trick then into doing our bidding rather than having them do what they "think" we want.
01-11-2018, 08:20 AM - 1 Like   #10
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If you have HSS available on the flash, you can use it. It will be using full power for each shot though, so you may want to give the flash a substantial break between shots. The aperture of the flash can be set to a higher numbered aperture to direct the light to a more concentrated area if the flash is in Manual mode.
01-11-2018, 08:38 AM - 1 Like   #11
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From the appearance of the photo you posted, it looks like the flash did its job as expected. The "blur" I see is a combination of motion blur due to the 1/180th second shutter speed and enough ambient lighting to expose during that time, and some just out of focus elements due to the bird moving away from the correct focus point by the time the flash went off.

Keep in mind that the camera waits 1/180th of a second (time for the shutter to get fully opened) before it fires the flash, and with some fast moving subjects that can capture a picture different than the one you saw in the viewfinder.

It appears that if the ambient light were a bit weaker, motion blur would have been mostly eliminated but then that might not set the correct exposure for the surrounding tree limbs, etc. You can't decrease your aperture because that will decrease the ambient exposure and your flash. Increasing your aperture will probably overexpose the subject.

That leaves the solution of a higher powered flash (or closer subject distance) and smaller aperture so the ambient light will have less effect in the 1/180th second exposure (which has already been stated in previous posts). Otherwise, it needs to be darker when the photo is taken (which may cause undesirable effects in the background exposure).

The best way to see if your existing equipment is up to the task is to start working off that overindulgence with some test shots. You're definitely in the ball park on this one and if the bird had been a bit more still, it would have been a keeper. If you start mixing with the birds, they will get less nervous and pay less attention to you so better shots are in your future. Or do like I do and cheat with a tame species like the gray jay which will jump on your lens if they see food.
01-11-2018, 09:49 AM   #12
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QuoteOriginally posted by Skodadriver Quote
making the shutter speed slower rather than faster has made me seem awfully stupid.
Hahaha on the contrary! You just don't know how many blunders I took before getting my head around flashes, and I still only use manual because it's easier!

QuoteOriginally posted by Bob 256 Quote
*snip*

You can't decrease your aperture because that will decrease the ambient exposure and your flash.
Well, technically he could, because we've already established that the flash wasn't at full power, and that he still had some leeway, albeit not much (less than a stop, I think).

QuoteOriginally posted by Bob 256 Quote
That leaves the solution of a higher powered flash (or closer subject distance) and smaller aperture so the ambient light will have less effect in the 1/180th second exposure (which has already been stated in previous posts). Otherwise, it needs to be darker when the photo is taken (which may cause undesirable effects in the background exposure).
That Sigma is among the most powerful flashguns one can buy (GN 61 m at ISO100)... not much to improve there.
01-11-2018, 12:49 PM   #13
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QuoteOriginally posted by LensBeginner Quote
That Sigma is among the most powerful flashguns one can buy (GN 61 m at ISO100)... not much to improve there.

After receiving the flash I looked for a manual to download and found somebody tested this Sigma and suggested the GN was nearer 45m than 61m but never mind, it is pretty powerful.
Once I feel better I shall start reading up on using flash, HSS etc.
Thank yous to all contributors. Happy new year to you all.
01-11-2018, 01:07 PM   #14
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At full or even half power, many hotshoe flashes won't have a duration low enough to counter the movement of a little birds wings. You might look into a "better beamer", which is a big fresnel lens that straps on to your flash to concentrate the light forward so you can use a lower power setting. I don't have one, but they are handy for telephoto use with wildlife (e.g. Visual Echoes FX3 Better Beamer Flash Extender for Use FX3 B&H).

Another option is a wireless flash trigger. This lets you get the flash closer to the subject and use lower power, and also the massive benefit of being able to position the light in a more natural off-axis location. You'd need to know where the birdie is going to be beforehand. This isn't super hard in your back garden, set up bird feeders with nice looking perch nearby and aim your flash there and wait patiently.

Within the 1/180s sync speed, ambient light is the killer with respect to motion blur. If the subject moves you'll see ghosting like in your image, especially visible if the background is bright. If you really want to freeze fast motion, you need to kill the ambient, or specifically, kill the ambient on and behind your subject. Positioning yourself so the bird has a naturally dark background can help.

Good luck and enjoy your flash!
01-11-2018, 01:48 PM   #15
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I've tried both ways of using flash to capture a moving bird. If the ambient light is low, flash can freeze the subject fairly effectively, but the results can be rather harsh. HSS works in a wider range of ambient light, and allows more of a "fill" effect, because you are relying more on the shutter speed to freeze the motion. But because the output from the flash falls off exponentially as the speed increases, I find I am often limited to a speed like say 1/320th, which might not be enough to stop motion blur. The other issue with HSS is that it relies on P-TTL, and that means there's quite a lag between pressing the shutter button and the flash firing (it needs to take a reading first). In the meantime the nicely focused subject has often moved.

Despite the difficulties, I still think flash is worth persisting with in dull conditions - because without it you need to drop the shutter or raise the ISO to an extent likely to severely reduce the image quality - especially with a K-5 and a slow lens like the DA 55-300. Flash also makes a big difference for fill, for example where there are harsh shadows.

What @BrianR says about the value of fresnel flash extenders is right. I've tried several. The Rogue Safari is cheap and simple - it concentrates the beam from the popup flash. (More info here: Rogue Safari Flash Extender - PentaxForums.com) Here are some examples with it.




For these shots I turned down flash exposure compensation to something like -1.3EV to -2.0EV, and underexposed the image a bit. The "steel eyes" effect occurs more because the flash beam is so close to the lens. You get less of this effect with a speedlite because it's a bit higher. No doubt Brian's suggestion of off-camera flashes would be better in this regard too.

The Better Beemer that Brian mentioned is one that sits on the speedlite flash. I've used the JJC equivalent which is quite cheap and effective, attaches with Velcro and is light-weight and folds up flat - but I broke the fragile plastic mounting point without doing much. I'm now using the much more expensive and heavier MagBeam Wildlife kit and it seems a lot better. The downside is that a 500g flash (Metz 58 AF1) plus the MagBeam is a lot of weight perched on the hotshoe.

More on these and other options linked here: Flash/flash amplifier recommendations with 600mm f5.6 or 150-450 lens (bird photo) - PentaxForums.com

Last edited by Des; 01-11-2018 at 06:16 PM.
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