Flash, shutter, Aperture in the sun

[courtneyc]

In reading posts on this forum some if the posts about shutter/aperture seem counterintuitive to what I would guess and I wanted to try to get some clarification.

DOF and movement aside.. If I have Aperture of 16 and a shutter speed of 200, and a speedlight. I would think that opening the aperture by one stop and increasing the shutter speed by one stop would make the relative power of the flash higher to the ambient light.

I saw several posts mentioning that closing down the aperture made the load on the flash lighter. To me this seems backwards. I'm obviously missing something.

If someone could please explain what would differ in the exact same picture, with the same composition, where DOF and movement wasnt a concern, what final effect on the picture would changing aperture vs shutter speed have (and obviously moving the other to compensate)

Here are a couple pics where I was trying to figure out myself but using myself as a model makes it hard for me to see what I'm doing and really get results that I can count on to tell me anything useful.

Mind you I'm very new to photography (I just got my camera on Friday) so I could be completely missing the boat here.

Thanks!

-c

[Dermit]

Closing down the aperture makes the flash work harder... makes the load greater. Keep in mind that closing down means larger numbers so f/16 is closed down more than f/5.6


changing the aperture and shutter to accomplish the same exposure value (EV) has no other effect than on the motion and DOF... other than also there is usually a 'sweet spot' of most lenses where the image quality is best at certain apertures.... which is not full open or full closed.... somewhere between f/5.6 and f/11 for most.

[courtneyc]

Closing down the aperture makes the flash work harder... makes the load greater. Keep in mind that closing down means larger numbers so f/16 is closed down more than f/5.6


changing the aperture and shutter to accomplish the same exposure value (EV) has no other effect than on the motion and DOF... other than also there is usually a 'sweet spot' of most lenses where the image quality is best at certain apertures.... which is not full open or full closed.... somewhere between f/5.6 and f/11 for most.

Not sure if your agreeing with the conclusion I have in my head. You mention that stepping the aperture down makes the flash work harder, but I'm not sure if you simply mean because its darker. I'm assuming that the exposure value is the same between two images so the shutter is adjusted to compensate for the aperture change.

The way it seems to me is that opening up the aperture would require you to speed up the shutter to keep the same exposure value. Using the flash and taking the picture (assuming the flash is full manual) you would get more light from the flash as before, and at the same time, less of the ambient light. It also seems that by adjusting the shutter alone I would really only be cutting out the ambient and not impacting the light picked up from the flash.


SO (not quite thinking out loud.. thinking into the box)

(ignoring movment and DOF)

aperture allows more of the flash, and ambient in when opened up.

shutter really impacts the ambient (so long as the shutter is slower than the flash)...

so in that sense the picture exposure can change dramatically with a flash even if you keep the same EV when you adjust the shutter to compensate for the aperture change.

Do I have something wrong here? or did I hit it spot on?

[courtneyc]

nevermind i just did a test..

took a shot...closed down aperture 3 stops... shutter 3 stops faster... same ev.. took another shot.. looked pretty much the same.

got the flash.. took a shot looked normal.. closed down aperture 3 stops... shutter 3 stops faster.. same ev.. took another shot.. flash much more overpowering to the ambient.

Sorry to muck up the forum with something I could test and figure out.

:)

[Mark1]

Think of light as if it were different speeds. Ambient light is slow, flash is fast. -- Not really but work with me-- The apature will work with the flash to only let so much in, because in a flash its gone. ( pretty punny i know!) The shutter will work with the ambient as it needs time to get there.

You will start to notice the biggest difference in settings changes when the ambient can easily be over powered by the flash. Try the test again, but stand up. Your back ground is getting washed with the flash at all the speeds. With subdued ambient you will be able to bring out the background with the longer shutters.

Read this, It has helped others...
http://strobist.blogspot.com/2007/09/lighting-102-balancing-light-twilight.html
http://strobist.blogspot.com/2007/09/lighting-102-31-balance-flashsun.html
http://strobist.blogspot.com/2007/09/lighting-102-33-balancing-flashambient.html

[courtneyc]

mark.. perfect. thanks... great links.. it turns out the way it was in my head is correct after all (apologies for my poor ability to communicate exactly what I was getting at)

[Mark1]

Its basically playing with equivalent exposures. Only they are not really equivalent. The subjects may be the same in each exposure. But the backgrounds need the extra shutter to fill in.


Oh, and, my wife thinks we could be brothers. She thinks we look kinda alike.

[DDCSD]

One thing that I did not see clarified here is why shutter speed has no effect on the flash exposure. The flash will fire at about 1/1000s (very general, every flash varies, and the power setting will cause even further variation). This is why the shutter speed does not come into play, the flash is only illuminating the subject for the 1/1000s, so actual shutter speed will only affect the ambient (as you figured out).

The best thing to do is to think of flash photography as making two separate exposures, ambient and flash. The shutter speed only affects the ambient exposure, not the flash. ISO and aperture is the only way to adjust your flash exposure (except adjusting the flash's power output).

ISO, aperture and shutter speed are all taken into account for the ambient exposure, but adjusting shutter speed alone is the usual method to reduce or increase the ambient exposure. The reason is that adjusting the shutter speed will not mess up your flash exposure (as long as you don't exceed you camera's sync speed).


The following examples all assume a consistent flash power setting in manual. ETTL adjusts the flash power automatically, so until you reach your flash unit's max power, the exposure should look about the same.

A low ISO (ISO 100) is not near as sensitive to light, so the flash exposure will be darker than if you use ISO 800.

A narrow aperture (f/16) will not let as much light through the lens as a wider aperture (f/4). With less light reaching the sensor, your flash exposure will be darker.

Here is an amazing resource for flash photography:
http://planetneil.com/tangents/flash-photography-techniques/

[Mark1]

One thing that I did not see clarified here is why shutter speed has no effect on the flash exposure.

I didnt mention it because it sounded like that part he already understood. I took his question as pertaining only to the background.

great link by the way!

[DDCSD]

I didnt mention it because it sounded like that part he already understood. I took his question as pertaining only to the background.

great link by the way!

Yep, I just felt like typing. ;)

That site probably did more to improve my photos overnight than anything else.

[Mark1]

Actually it was good to add. There may be some readers that didn't catch it and you filled it in for them!

[courtneyc]

One thing that I did not see clarified here is why shutter speed has no effect on the flash exposure. The flash will fire at about 1/1000s (very general, every flash varies, and the power setting will cause even further variation). This is why the shutter speed does not come into play, the flash is only illuminating the subject for the 1/1000s, so actual shutter speed will only affect the ambient (as you figured out).

The best thing to do is to think of flash photography as making two separate exposures, ambient and flash. The shutter speed only affects the ambient exposure, not the flash. ISO and aperture is the only way to adjust your flash exposure (except adjusting the flash's power output).

ISO, aperture and shutter speed are all taken into account for the ambient exposure, but adjusting shutter speed alone is the usual method to reduce or increase the ambient exposure. The reason is that adjusting the shutter speed will not mess up your flash exposure (as long as you don't exceed you camera's sync speed).


The following examples all assume a consistent flash power setting in manual. ETTL adjusts the flash power automatically, so until you reach your flash unit's max power, the exposure should look about the same.

A low ISO (ISO 100) is not near as sensitive to light, so the flash exposure will be darker than if you use ISO 800.

A narrow aperture (f/16) will not let as much light through the lens as a wider aperture (f/4). With less light reaching the sensor, your flash exposure will be darker.

Here is an amazing resource for flash photography:
http://planetneil.com/tangents/flash-photography-techniques/

I'm staying far away from any automatic setting like the ttl until I have a firm grasp over what is going on, and how to produce the exact results I want manually. Kind of means I could have gotten by with a much cheaper flash, but I'm figuring that later on when I do have a better grasp of the manual process the ttl can help with automating what I already know I would do manually... and I'm having to fight the urge to buy more lenses and lighting until I get the hang of the ones I have (I just about ordered another 580, and an 85L earlier today..)

Just helps me to understand better to forget about everything automatic at first. :)

and thanks.. great link... I'm sure my shots will be pretty bad for a while (like the ones above which are really more tests than real shots) but i'm eager to learn :)

-c

[courtneyc]

Its basically playing with equivalent exposures. Only they are not really equivalent. The subjects may be the same in each exposure. But the backgrounds need the extra shutter to fill in.


Oh, and, my wife thinks we could be brothers. She thinks we look kinda alike.

hah. I dont get that very often. Where's the self portrait?



oh yeah, on a side note. with how cheap and bright vivitar 285HV's are. wouldn't it make a lot of sense to just load up on them for cheap studio lighting? flexible, portable.. and cheap. Of course the drawback is the lack of a modeling lamp, but for someone starting out buying equipment stuff that can be used outdoors, is portable, and also could be used in a studio environment seems like a smart path.

thoughts?

[Mark1]

Modeling lights, in my opinion, have lost a lot of clout in the age of digital. You can chimp and see real results rather than think you are seeing what you will get, but with weaker lights. If you want to get in the world of small flashes, as opposed to studio strobes, I would get a variety of strength flashes. There may be times you want a weaker one. And it may be easier to use it, than choke down a stronger one. But be prepared to spend the money! The world of small flashes is not necessarily cheeper than strobes. Example 580's are about $400, Alien Bees B800 are about $279+ extras

No self portrait to post, However I do see what she means. But it looks like I'm a bit "bigger boned"

[courtneyc]

Modeling lights, in my opinion, have lost a lot of clout in the age of digital. You can chimp and see real results rather than think you are seeing what you will get, but with weaker lights. If you want to get in the world of small flashes, as opposed to studio strobes, I would get a variety of strength flashes. There may be times you want a weaker one. And it may be easier to use it, than choke down a stronger one. But be prepared to spend the money! The world of small flashes is not necessarily cheeper than strobes. Example 580's are about $400, Alien Bees B800 are about $279+ extras

No self portrait to post, However I do see what she means. But it looks like I'm a bit "bigger boned"

The one I have is a 580exII. I was planning on getting a second 580exII then several vivitars.

Specifically I was curious if vivitars are not that popular and if so howcome. They are damn cheap. They seem to be usable as good workhorse lighting moreso than a bunch of $400 lights (considering they are nearly as bright as 580's i believe its pretty alluring).

I'm ok with spending money where its required, but if I can get the same job done with something 1/4 the price it seems silly not to...

Also, why would it possibly be better to have a weaker one than choke down a stronger one? Would there be instances that using a weaker canon speedlight would be preferable to choking down a 580? if so why?

Sorry for so many questions in one post, but I'm new afterall :)

-c

[Mark1]

When using them off camera the only key for me is that they have manual control. Vivitar and others are downed because they carry no reputation. They simply don't impress anybody. But they work fine. Its like the moped theory. They are very useful and get the job done, you just dont want your friends to see you on one. I have a old Sunpack I use as a second flash. Its not a 580 by any means. But it works 100% of the time. So get what you want and use it. They are a lot cheaper to replace when they break.

Times you want a weaker one is for fill. Its easier to control it when it only gets so bright. Sure the 580 are very controllable. But its very easy to over light.I have always had a small flash for times I dont want it very bright. It just seemed like the thing to do. Want a weaker light... then use a weaker light.

Now that i think about it. If you are buying the stuff get it all the same. I have just kept my older stuff as I moved up the ladder. It still works so I use it. But if I were to buy it all now. I would get matched pairs. Much like you are stating.

[DDCSD]

If you have a 580EXII, I'd get a 430EX next. It is only one stop less powerful than the 580 and is half the price.

There is nothing wrong with the Vivitar's, except some shoddy quality control. I think they have even quit new production on them, but they may have restarted in the last few months.

The Sunpak 383 is also a popular cheaper flash.

www.strobist.com that Mark mentioned earlier may be exactly what you are looking for. Be sure to spend some time exploring that site.

[Mark1]

And don't ever get catch yourself thinking "I know all of this now" There is always something new to learn. I have been shooting for almost 20 years, and I still find new stuff to add to my bag of tricks.

[courtneyc]

Thanks for all the input.... I suppose I should get at least one more canon and play with the two lights before I worry about what kind of lighting to get next.

I'm not too worried about me thinking "i know all of this" i always operate under the assumption that no matter how much you know about any subject, you know zilch compared to what could be known... On that note, it seems important that people experiment doing things "wrong" just to see if another way to do things "right" can be found... and a study of others ways of doing things is, of course, important on an ongoing basis (hence me joining this forum).

Anyway I really appreciate the input. I think the lighting stuff is, at this point, the most alluring part of photography for me..

-c

[PhotosGuy]

On that note, it seems important that people experiment doing things "wrong" This might shorten your learning curve. Post #3
Tips for Xmas Ball Please (http://photography-on-the.net/forum/showthread.php?t=419399)