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04-08-2010, 07:34 AM   #1
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Portrait Lens and Flash

I've heard/read a number of times the following statement...

"It's a great lens, a little soft wide open but that's good for portraits"

For example the Jupiter-9 85mm f2 lens.

I've tried to use it wide open with flash but my photos are almost always overexposed. In fact if I set the camera/lens to iso 100, f2 and sync speed (180) even without flash the pictures are sometimes overexposed from the ambient light. Adding flash would only make it worse.

Does this statement refer to casual portraits without flash or should I be shooting in the dark and adding flash to get the look I want?

Thanks -Dave-

04-08-2010, 07:37 AM   #2
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My favorite combo has become the FA 77mm ltd on my MZ-3 or K20d with or without flash. The Jupiter is a good budget option for this range. I didn't want to pay ~$300+ for one of the various MF 85mm Taks/Pentax lenses. I'm still on the lookout for a auto-tak 85mm. I try to bounce the flash if possible or diffuse it if not. Some people rant against the light sphere, but I keep that as an option when I can't bounce the flash.
04-08-2010, 07:43 AM   #3
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Hi Blue

Can you shoot with the FA 77mm ltd wide open with flash? Or do you have to stop it down a bit when using flash?
04-08-2010, 07:55 AM   #4
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QuoteOriginally posted by dmoon911 Quote
Hi Blue

Can you shoot with the FA 77mm ltd wide open with flash? Or do you have to stop it down a bit when using flash?

I have on the K20d but I also use a Metz 48 flash which may help. The flash AND k20d bodies (k200d also) have controls that effect the flash power, color etc. The key is to practice with your setup. My biggest gripe with the p-ttl is that pre-flash can cause people to close their eyes. I have less problem with that on X-sync with the K20d.

04-08-2010, 08:00 AM   #5
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Wait, don't pentax cameras fire flash on full power when you put an M42 lens on camera? You'll need to switch the flash away from PTTL, and choose Auto mode or Manual mode (that is, assuming your flash is a PTTL/TTL model)
What flash do you have?
04-08-2010, 08:04 AM   #6
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QuoteQuote:
I have on the K20d but I also use a Metz 48 flash which may help. The flash AND k20d bodies (k200d also) have controls that effect the flash power, color etc. The key is to practice with your setup. My biggest gripe with the p-ttl is that pre-flash can cause people to close their eyes. I have less problem with that on X-sync with the K20d.
I've heard the thing about preflash maybe a gazillion times - but I've never seen the flash actually doing it!! How comes? I used a PTTL flash on both K-x and K-7, and I never noticed any kind of pre-flash - the flash just fires as the camera takes a picture. The exposures are good, too, - the K-7 is always spot on. What's "wrong"?
04-08-2010, 08:44 AM   #7
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QuoteOriginally posted by pbo Quote
I've heard the thing about preflash maybe a gazillion times - but I've never seen the flash actually doing it!! How comes? I used a PTTL flash on both K-x and K-7, and I never noticed any kind of pre-flash - the flash just fires as the camera takes a picture. The exposures are good, too, - the K-7 is always spot on. What's "wrong"?
In the daytime it isn't that obvious to the photographer. Its possible you aren't firing in the p-ttl mode. I have a bunch of images with the eyes closed until I started trying to mitigate that. You should see the pre-flash in a dimly lit room. This isn't exclusive to Pentax either. Others do it as well, Pentax may be the worst at it.
04-08-2010, 08:49 AM   #8
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QuoteQuote:
In the daytime it isn't that obvious to the photographer. Its possible you aren't firing in the p-ttl mode. I have a bunch of images with the eyes closed until I started trying to mitigate that. You should see the pre-flash in a dimly lit room. This isn't exclusive to Pentax either. Others do it as well, Pentax may be the worst at it.
'

Hm... How much lag is there between the preflash and actual flash? I use P-TTL almost all the time - and never noticed the preflash, even if I take the eye off the viewfinder. Does it have anything to do with me bouncing the flash?

04-08-2010, 08:59 AM   #9
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QuoteOriginally posted by pbo Quote
...and I never noticed any kind of pre-flash
Ditto here. When I use either 360 or 540 mounted to my K20D and shoot in P-TTL mode, and I don't notice any pre-flash and usually the exposure is spot-on, although I have the flash compensated at +0.7.

I know the technical description of how P-TTL works does say there is a pre-flash followed almost instantaneously, by the secondary camera-directed flash, yet I have not seen any unusual amount of closed-eyes on my subjects so far.

Lately I've been playing with these two flashes together in Manual Mode in reduced intensity, triggered wireless by the on-board flash of my K20D, with/without diffusers, and bouncing off the walls and ceiling. I've gotten to a stage where I usually get the exposure within one stop the first time.
04-08-2010, 09:18 AM   #10
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QuoteOriginally posted by pbo Quote
'

Hm... How much lag is there between the preflash and actual flash? I use P-TTL almost all the time - and never noticed the preflash, even if I take the eye off the viewfinder. Does it have anything to do with me bouncing the flash?
Bouncing helps a lot.

Edit: I'm not going to argue with you guys about it. However, the system uses a pre-flash to determine ttl, that what is is meant by p-ttl. Some people are sensitive to it. A blink of an eye is p.d.q.
04-08-2010, 09:44 AM   #11
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I have a af540fgz, 2x af280t and a af200t.

I haven't used the 540 in pttl very often because only a handful of my lenses support it. I have noticed the pre-flash when I did use it, but it's more like a flicker to my eye, but then again it might be because I was looking for it.

In this case even if I use the 540 on manual and 1/32 (I believe that's the lowest power setting) it's still too much. If I could increase the shutter speed I could fix the problem but then I would be past the sync speed and have all new problems.
04-08-2010, 09:53 AM   #12
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QuoteQuote:
In this case even if I use the 540 on manual and 1/32 (I believe that's the lowest power setting) it's still too much. If I could increase the shutter speed I could fix the problem but then I would be past the sync speed and have all new problems.
Some things that come to mind - that would make flash less powerful:
1) bouncing off the ceiling if present, or using the bounce card on the flash
2) putting on some flash softener (like, an omnibounce or some flash "softboxes"/reflectors/etc.) to suck out power
3) sticking a neutral density gel on the flash head - weakens the flash output by some fraction.

Might help!
04-08-2010, 10:35 AM   #13
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That might help, and I've actually got some umbrellas and some diffusers on the way. My only worry is that if the room is too bright to begin with (ie overexposed at iso 100, f2 and 180) adding flash no matter how little will make it worse.

So I guess what I need to ask is... is it worth shooting at f2 to take advantage of the narrow depth of field and soft filter with no flash, or should I adjust the aperture for proper exposure at say f8 and allow a lot more freedom for lighting?

If the latter is true what is the advantage of having a portrait lens that is nice wide open if you can't use it wide open?
04-08-2010, 11:38 AM   #14
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QuoteQuote:
That might help, and I've actually got some umbrellas and some diffusers on the way. My only worry is that if the room is too bright to begin with (ie overexposed at iso 100, f2 and 180) adding flash no matter how little will make it worse.

So I guess what I need to ask is... is it worth shooting at f2 to take advantage of the narrow depth of field and soft filter with no flash, or should I adjust the aperture for proper exposure at say f8 and allow a lot more freedom for lighting?

If the latter is true what is the advantage of having a portrait lens that is nice wide open if you can't use it wide open?
Wait a minute... If the room is too bright, why would you want to use the flash in the first place?

Or do you want to shoot portraits with bright backgrounds (lit with ambient light) and subject (model) lit with flashes? Then you need to put the model in the shade or facing away from the sun/windows/bright stuff (it also relieves the eyes, by the way), and light with a flash (or you'll get a silhouette).
04-08-2010, 11:51 AM   #15
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QuoteOriginally posted by pbo Quote
Hm... How much lag is there between the preflash and actual flash? I use P-TTL almost all the time - and never noticed the preflash, even if I take the eye off the viewfinder. Does it have anything to do with me bouncing the flash
Because the pre-flash strobe is used for metering, the mirror has to be down during the pre-flash strobe (to reflect light to the light sensors). In practice, the pre-flash strobe happens just before the mirror going up. IIRC, the time lag between the pre-flash and the main strobe is around 1/50 sec.

To see the pre-flash, take a photo in p-TTL mode and the camera in 2 sec delay mode.

My son recently develops sensitivity to the pre-flash. His eyes are closed in all photos taken in p-TTL mode. I've never used p-TTL when photographing a group of people.
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