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08-20-2012, 01:07 PM   #1
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AF 540 FGZ: P-TTL with Background

I am receiving my flash soon from B&HPhoto and seeing some photos taken with a flash, I'm curious in how to shoot the way these photos I've seen are shot. In P-TTL mode with the AF 540 FGZ, how do I light up the subject with the background still exposed beautifully as if I were shooting the background only without a flash?

In P-TTL is it possible to shoot this photo except with the couple being lit-up as well as the beautifully exposed background being the way it is? Or will I need to manually set-up the flash and camera settings for such a photo?

http://favim.com/image/110316/



Last edited by LeDave; 08-20-2012 at 01:13 PM.
08-20-2012, 01:36 PM   #2
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Yes, set the camera on Manual and adjust the exposure for the background, now turn on the flash and set the metering point on the couple and take a photo.
08-20-2012, 01:39 PM   #3
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This is slow flash sync. With the Sigma flash, you select this from the K-5's flash menu. I presume it's the same with the Pentax flash.

The K-5 manual is contradictory. On p.78, it says it slow sync can be used in P, Av, Sv, but on p. 182 it refers to using it in Tv mode. If you experiment you'll find it's only available in P, Av, Sv.

This is the "evening lookout" setting. When you have a person or group at a lookout and you want to capture the city or scene behind them. Since it will a long exposure, instruct the subject(s) to keep as still as possible.

Dan.
08-20-2012, 01:50 PM   #4
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Thanks guys!

08-20-2012, 02:19 PM   #5
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I would do it like this: With your flash turned off, find the "proper" exposure for the background with the camera in manual mode, use the green button if you're not sure. Take a shot. If you're unhappy with the background exposure, adjust the shutter speed, but leave the aperture and ISO alone. Once you're happy with the background, turn the flash on, and make sure the active auto focus point is on your couple. That should get it right, but if your couple is a little too bright or too dark adjust the flash EV compensation (not the camera EV comp)
08-20-2012, 02:19 PM   #6
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LeDave, in the image you posted you had the couple in focus and the background OOF. I used a deep DOF for a different effect.

I was taking cityscape shots of Brisbane from the Kangaroo Point Cliffs and parklands in Dec 2009 with a K20D. When I switched to portrait orientation with the prime I was using (Pentax-M 50/F1.7, I think), there was too much plain foreground near the bottom of the frame. So I asked a friend to go sit down on the riverbank rocks so I could add him into the composition. The young man died within a year from a tragic car accident in Fiji, so I went back to this image to prepare to send it as a memento to his parents of the good times during his visit to Brisbane. The young man was quite dark in the original image as I wanted a silhouette. However, I reprocessed the image, masked him, and dodged him so his features became more recognisable. His parents and older brother liked the shot.





Dan.

Last edited by dosdan; 08-20-2012 at 02:28 PM.
08-20-2012, 03:58 PM   #7
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Remember to set the flash to "Trailing Shutter Sync" for these kinds of shots, that way you get the correct exposure for the background then just before the shutter closes the flash fires, this will give less blur on the flashlight subject in the foreground.

08-21-2012, 12:52 PM   #8
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QuoteOriginally posted by cmohr Quote
Remember to set the flash to "Trailing Shutter Sync" for these kinds of shots, that way you get the correct exposure for the background then just before the shutter closes the flash fires, this will give less blur on the flashlight subject in the foreground.
It wont actually.
The difference is however that you get trailing headlights for example, that looks more natural.
08-21-2012, 04:23 PM   #9
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Well, Yes, It does "actually" as I say Help, and a better flash technique for these kinds of shots .... Notice I say "less blur" not eliminate blur, it helps make the blur less noticable, its what the trailing shutter sync was designed for, slow shutter speed fill-flash situations. The fact that you can be creative with trailing shutter sync for motion shots and the like is a bonus.
08-21-2012, 05:54 PM   #10
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QuoteOriginally posted by cmohr Quote
Well, Yes, It does "actually" as I say Help, and a better flash technique for these kinds of shots .... Notice I say "less blur" not eliminate blur, it helps make the blur less noticable, its what the trailing shutter sync was designed for, slow shutter speed fill-flash situations.

How does it reduce blur? Say you have a 10s night-time exposure of a group at a city lookout.

First curtain flash sync:
Shutter opens and flash fires...
Shutter stays open 10s and then closes.

Any subject (in the group) motion after the flash fires can still cause a faint motion blur, which may be visible

Second curtain flash sync:
Shutter opens for 10s... j
Just before the shutter closes, the flash fires.

Any subject motion that occurs before the flash can still cause faint motion blur, which may be visible.

As far as I'm aware, the same amount of motion blur will be visible in both situations, but leading the subject with 1st curtain sync, and trailing the subject with 2nd curtain sync.

So how does trailing curtain sync produce less visible motion blur?

If this "blur reduction" was the principal purpose of 2nd curtain flash sync, why is this property not mentioned in the following links?

Flash synchronization - Wikipedia, the free encyclopedia
Flash sync - Camerapedia
Slow Sync Flash

Note: for those who want to see a demo of 1st & 2nd curtain flash sync (I can't see a significant difference in subject motion blur between the 2 shots in this comparison), see:

https://www.pentaxforums.com/forums/accessory-memory-articles/90096-compariso...ync-flash.html

Dan.

Last edited by dosdan; 08-21-2012 at 07:06 PM.
08-21-2012, 09:33 PM   #11
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You are making two exposures, one for the background ambient light, one for the flash. Your flash will light your couple but not a city skyline.

Ambient factors: Aperture, ISO and Shutter Speed.
Flash factors: Flash power, Flash Distance, Aperture & ISO. Shutter speed doesn't matter, except max 1/180 with Pentax.

The flash is very fast so any shutter speed lower than 1/180 will work for the couple. If you drag the shutter (leave it open for a relatively long time for the ambient light), then use rear curtain so the couple is illuminated at the end of the exposure instead of the beginning. That way any movement by the couple won't be seen, the flash will "freeze" them.
08-21-2012, 09:51 PM   #12
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QuoteOriginally posted by Ponosby Britt Quote
If you drag the shutter (leave it open for a relatively long time for the ambient light), then use rear curtain so the couple is illuminated at the end of the exposure instead of the beginning. That way any movement by the couple won't be seen, the flash will "freeze" them.
The flash will freeze them for 1/10,000th of a second (roughly) regardless of at which end of the exposure the other 9,999 occur. Front/rear curtain only matters if you are photographing moving subjects that emit light. With front curtain sync the trails of light will appear in front of a moving object, with rear curtain sync they will be proper light "trails", and trail behind the subject. For this hypothetical situation one choice is just as good as the other.

Last edited by maxfield_photo; 08-21-2012 at 10:02 PM.
08-22-2012, 01:04 PM   #13
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QuoteOriginally posted by cmohr Quote
Well, Yes, It does "actually" as I say Help, and a better flash technique for these kinds of shots .... Notice I say "less blur" not eliminate blur, it helps make the blur less noticable, its what the trailing shutter sync was designed for, slow shutter speed fill-flash situations. The fact that you can be creative with trailing shutter sync for motion shots and the like is a bonus.
That's the thing it won't lessen the blur or make it less visible and that part of your comment i commented on saying it isnt true.

The difference is in the lights if they are leading or trailing.

08-22-2012, 06:15 PM   #14
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Mea culpa. My intent was that if the ambient exposure was long enough and there was enough light to see the couple a little bit and they moved after the flash fired it might look a tiny bit blurry but if the flash fires as the last thing it would mask the maybe really small imperceptible inconsequential potential blur. Mea culpa.
08-23-2012, 12:21 AM   #15
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Exactly, as I said, lessens the effect, not talking about pixel peeping, Look at the pic of the train, which "looks" sharper to your eye, looking at the pic as a whole??? Ask a group of people which looks better, Your pictures prove exactly what I'm saying, there is a nice sharp edge at the front of the train, your brain sees this and sees the image as being sharper and more detailed. We are actually agreeing about this, but my comment are more based in what people see, not what happens at a pixel scale.

Beyond the technical reasons, There is also "real world" applications and circumstances that "facts and figures and pixel peeping" dont take into account. What is the first thing 95% of people in front of your camera do the very moment after you take a photo?....Move......And as a photographer you need to do what little you can to control whats happenning infront of you to get a greater success rate. That very moment that flash fires, people assume the photo is taken and its over, they unconsiously relax their pose, some People immediately turn to talk to the person beside them, some people uncontrolably"flinch" after the flash as a result of the flash itself (even when they know its coming), groups of people move and stop posing, some people are even walking away (even when you explain what you are doing and ask them to say still!!!) Babies turn and stare at where the big flash came from, some animals run, some birds fly off, These are all things you as a photographer have little to zero actual control over, So if you are using Leading shutter, your flash fires yet you've still taking the photo for the next half a second or so, up to 5 ,6 or even 10-30 seconds, you will get more blur in your photo than with trailing shutter, where the bulk of your exposure is done with subjects remaining still until the exposure is over the millisecond after the flash fires, so any resulting movement of your subject caused by the flash firing is not captured, thus increased success rates and sharpness (less blur) for photos, so effectively Trailing shutter sync as a technique can increase sharpness and help reduce blur over leading shutter sync as a technique when applied to these kinds of photos. Leading and Trailing shutter sync is not just about the mechanical relationship of the camera and flash , but everything as a whole, the camera flash setting is just a part of the Technique not the whole technique. In photography, using a good, tried and tested technique to help increase keeper rates and in some cases ensure a one time only oportunitity has the most chance of success, is not a bad thing.

I'm sorry, but all too often people are too quick to jump up and tell others on the internet they are "wrong", and I could have made a better answer that to come back with a retorical "No... Actually" to somebody saying "It won't, Actually", but thats the internets for you, and I'm sorry about that. Arvh's explaination of how to get the exposure settings was absolutely correct, I was just adding an extra tip to help achieve a good result, what I'm unsure about is why I was so shouted down and questioned so strongly by multiple people and had sample pictures thrust up in evidence of just how "wrong" I was (pictures that demonstrate a completely different application of the technique as well), for simply offering up an extra helpful tip when doing this kind of photography. As far as I'm concerned there is not a "wrong way" with leading or trailing shutter sync, but just what a person decides to use to produce the particular photo they are trying to achieve, to make that deciession they need to understand which will suit the particular application better. Only knowing that you turn a switch to set a camera/flash to a particular setting is only part of any technique, knowing why you do it and choosing when to use it and how it affects everything around you (not just the camera/flash) it's about applying skills.

So getting back to the OP's original post about not knowing about this kind of flash photography and getting a correct exposure reading for the background then using fil-flash, not motion based blurs with frozen subject, but, using longer shutterspeeds and fill-flash to achieve cityscapes with people infront with little to no blur at all, using trailing shutter sync is a safe place to "start out" to help get a good rate of keepers.
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