|
Forums >
Photography Talk >
How many power?
*Ack, I meant how much power Hey guys, I'm putting together an onlocation shoot in three weeks. I want to know how much power I need to shoot into the sun like this. I am wondering if renting one Profoto 7B 1200 w/s battery pack and head with beauty dish is enough...or would i need two 7B 1200s w/s battery packs and a twin head. What do you think?   Photos by Mike Ruiz Thanks, Mark Apr 19 07 11:15 pm Link 1 is enough if you are using a beauty dish and only need one light. If you want to use two seperate lights or start with softboxes, you may need two. If using two heads one main one rim or back light you would be better off with two seperate packs. The power from one is enough without the twin head unless you really want the background to be not only dark but rather black. You will likely need ND and a Polarizer on the lens or a fast sync on camera, unless you want to shoot at f 22 or more. Or can shoot at a very low iso, 50, 25, 6 even Stephen Eastwood http://www.PhotographersPortfolio.com Apr 19 07 11:24 pm Link My portable strobes, bare heads can knock the background down by a couple stops like your examples. 1200 should be more than enough. Apr 19 07 11:46 pm Link NYPHOTOGRAPHICS wrote: Care to expand a little for the severely flash challenged like ME? Apr 20 07 12:11 am Link Bryan Benoit wrote: Your polarizer/ND should give the adjustment on the box/package it came in. I think my CP needs +1 3/4 or +2 to compensate for the loss of light, otherwise everything will be underexposed. This took me a few shoots to figure out, couldn't figure out why everything was so dark after I metered everything perfectly. Turns out I forgot to compensate for the polarizer! Apr 20 07 12:18 am Link Brandon Ching wrote: thanks.. lost the box long time ago but you have pointed me into the direction that i need to follow.. I think... ;o) Apr 20 07 12:21 am Link OK, lets say the correct exposure for a typical sunny day is f16 at 1/100th at 100iso. You want the background dark, lets say three stops under exposed, so you need to start by upping your speed, but many current digital SLRs are limited as are some medium formats, so lets say you max at 1/200th flash sync speed. that gives you a correct exposure for the background at f11 at 1/200th at 100iso. Now you can make the background dark by setting your f stop to f22 and the background is two stops under, but maybe you dont want to shoot at f 22 or more. So now you place a Circular Polarizer on the lens, that can adjust you from 1.5 to 3 stops bringing your proper exposure to 1/200th at f4-f8 depending on how much you cut the light. But in order to get the background dark three stops you would still have to shoot at f11-f16 again you may not want to be there but rather shoot at f 8 or even f5.6 so you add a ND 1 stop 2 stop or 3 stop to the lens, lets say you start with a 2 stop ND filter, that can give you the following proper exposure 100iso 1/200th f5.6 for a three stop under you shoot at f16 now add a Circular Polarizer and dial it down to a proper exposure or 100iso 1/200th f2.8 for three stop under shoot at f8 Since you are actually adding a lot of ND and CP to the lens, you still need enough power from the flash to shoot as iff they were never there. So you still need to meter a flash at f 22 or more to over power the sky and subsequently overpower the fact that you have 3-4 stops of ND/CP on your lens. Stephen Eastwood http://www.PhotographersPortfolio.com Apr 20 07 12:26 am Link It is always better to have some more ND than you will need and more flashpower than you need since you cannot crreate more ND or Power, you can of course shoot at a great depth of field, numerically higher f stop or slightly underexpose a raw in processing if you shoot digital and shoot raw, but that is not a great way to start off, its better to do it the correct way to start. Stephen Eastwood http://www.PhotographersPortfolio.com Apr 20 07 12:30 am Link StephenEastwood wrote: thanks... not sure I understand all of it right now but will find a guinea pig this weekend and practice. Apr 20 07 12:31 am Link Could always go out and set an f stop of lets say f 8 shutter of 1/200th put on the ND/Polarizer you need to get the background dark enough for you and then and turn the flash up till it looks good, thats how I learned, and still do it.  Stephen Eastwood http://www.PhotographersPortfolio.com Apr 20 07 12:36 am Link just thought of something. Depending on if you are planning to shoot the model/subject full length or not. BUT if you plan on shooting the model full length you might want to go with a LARGE softbox. The beautydish won't reach her legs unless you back the light up. But if you do you may need more power. Apr 20 07 12:39 am Link StephenEastwood wrote: good idea... I do need to really understand what I am doing and why so that if conditions are ever different I will know what to adjust and why... Apr 20 07 12:41 am Link Chex wrote: thanks for the tip... at this point all I have is the beauty dish and a medium softbox at best... Apr 20 07 12:43 am Link I think I'll probably do two full bodies with the light atleast 10 feet away and a few 1/2 and tights at 2-5 feet away. I think for the wide 10 feet shots, I might need a second battery pack with the softbox. Opinions? Apr 20 07 12:47 am Link Mark M Gong Photograph wrote: As long as the light will still be able to kick out F/22 at 10' away. Apr 20 07 12:51 am Link 1200 ws from a profoto and hensel in a large silver lined SB with internal diffuser may be pushed and get about f 16-f22, without internal diffuser maybe 1/2 - 1 stop more. This all depends on what you want to shoot at f stop wise. A beauty dish without grid will spread enough for a full body at 6 feet, a beauty dish will overpower daylight at 10 feet at about f 22 or slightly higher for a white silver gains about 1 to 1/12 stops over that. Stephen Eastwood http://www.PhotographersPortfolio.com Apr 20 07 12:53 am Link Now if you want to have a little more fun, bring some gels for the lights, I most often use 1/4 to 3/4 blue for the lights which if white balanced for that on the model the background goes warm, or reverse and use warm on the model to get a blue cold look to the background, and if dark enough you can start to have a moonlit color begin. Of course you may need even more power for this as you are now cutting down the lights power with gels. Also works great on ringflashes  Stephen Eastwood http://www.PhotographersPortfolio.com Apr 20 07 01:08 am Link I get how polarizing filters will gain density in the background and reduce flare, but how does neutral density over the lens change the balance of strobe to background light? It effects both the same. It has the same effect that changing the iso does. The OP was worried about not having enough strobe power to overcome the level of the sun. That is a question of balance not volume. The factors that effect balance are volume/level of strobe and range of shutter sync speeds, not ND filters over the lens. Apr 20 07 07:21 am Link Dan Howell wrote: its a question of artistic vision, if the OP does not mind shooting with a larger depth of field than ND is not needed, if they want what is slightly more typical they will need to shoot at a smaller numerical aperature for that to happen you need to either sync faster or apply ND at which point the flash needs to be more powerful to overcompensate. You are right the effect is the same on the subject and background, but unless you can light the background and subject with flash you can let the background be effected and alter the effect of the subject to achieve what you want in both lighting and selective depth of field. For this to occur you need to be certain to have enough power to do it, otherwise you are back to sacrificing your artistic visions for lack of power/sync speed. Since he was looking to get a second pack and twin head I figured I would point out the amount of power one pack would supply and effects they can produce. To shoot at an aperature of 2.8 they would actually need a stronger pack and more ND and can just up the effect. Apr 20 07 10:38 am Link We could also add to this that if you want to go through a large softbox/jumbrella and move that box/umbrella 30 feet away yo lessen the effect of the fall off you would need more power, just as trying to use the head barebulb would from a large distance, but I figured that was starting to get too detailed and confusing, I was pointing out what the pack was capable of and that includes overpowering the sun plus controlling depth to a degree. Stephen Eastwood http://www.PhotographersPortfolio.com Apr 20 07 10:45 am Link We could also add to this that if you want to go through a large softbox/jumbrella and move that box/umbrella 30 feet away yo lessen the effect of the fall off you would need more power, just as trying to use the head barebulb would from a large distance, but I figured that was starting to get too detailed and confusing, I was pointing out what the pack was capable of and that includes overpowering the sun plus controlling depth to a degree. Stephen Eastwood http://www.PhotographersPortfolio.com Apr 20 07 10:45 am Link One off the best topics that i have read..!!! Especially with Stephens Eastwoods great tips. I am to in the same situation and i have a Profoto White beauty dish that is my only light (and i love it) I am thinking to get the Profoto AcuteB 600R (600watt) and i think this will be enough for most oof the photos Stephen i have read with intres the cell filter tricks.. Where on a Profoto Beauty dish you put them & wich colors u use? Apr 20 07 02:48 pm Link on a beauty dish you can place the gel in front of the dish as best you can with clips or gaffers tape, anywhere it sticks and causes the light to become colored is alright, the better the coverage the truer the color but either way it will tint the light. As for colors it really depends on the effect, if you are digital and you balance maually or dial in a kelvin you can create many effects, normally for swimsuit we would want a very warm model, problem is the warming gel on a model causes the sky which is not effected to get cooler in comparision unless you happen to have a beautiful warm red/orange sunset. Since I do not believe in relying on the sun I prefer to have control, I would actually cool the main lights by using a 1/2 ctb than adjusting to get 1/4 cooler making teh model 1/4 warm and the background 1/2 warm. but at times you may want to reverse that and warm the model 3/4 cto, and make the sky go blue in comparison, and when you darken it the sky gets a nice deep blue color. And yes all this can be done with multiple raw conversions, and adjustment layers and masking but why when you can shoot it right in the first place and fine tune it in post later. Stephen Eastwood http://www.PhotographersPortfolio.com Apr 20 07 04:34 pm Link the one thing to keep in mind is the more gels you use the more power you will need for the same effects, fine if you have extra power to spare but problematic if you do not. Stephen Eastwood http://www.PhotographersPortfolio.com Apr 20 07 04:37 pm Link |
