{"id":88,"date":"2007-12-26T03:42:39","date_gmt":"2007-12-26T08:42:39","guid":{"rendered":"http:\/\/planetneil.com\/tangents\/2007\/12\/26\/manual-flash-ttl-flash\/"},"modified":"2020-06-12T14:42:14","modified_gmt":"2020-06-12T18:42:14","slug":"manual-flash-ttl-flash","status":"publish","type":"post","link":"https:\/\/neilvn.com\/tangents\/manual-flash-ttl-flash\/","title":{"rendered":"Manual flash vs. TTL flash"},"content":{"rendered":"

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Manual flash vs TTL flash<\/h1>\n

For correct flash exposure, 4 things need to be controlled and balanced:
\n– aperture
\n– ISO
\n– distance (from the flash to subject)
\n– power (the flash’s actual blitz of light, taking into consideration any diffusion)<\/p>\n

Two things relate to camera settings, and two things relate to the flash itself.
\nTo really understand flash photography, it is essential to memorize those 4 things.<\/p>\n

If you need an acronym to remember things more easily: PAID
\nPower, Aperture, ISO, Distance.<\/p>\n

There are distinct ways in which flash exposure is controlled though –\u00a0Manual flash or \u00a0TTL flash<\/strong>.\u00a0(For the purposes of the explanation here, Auto and TTL flash can be grouped\u00a0together\u00a0wrt D-SLRs.)<\/p>\n

With manual flash, you<\/strong> have to adjust any of those settings to balance them out for correct flash exposure. You can use a light-meter, or even use the histogram to get correct flash exposure<\/a>.\u00a0With TTL flash, the camera and flash control the flash output (i.e., the power) as you adjust any of the other settings. That’s it in a nutshell – the differences between\u00a0Manual flash, and Auto \/ TTL flash.<\/p>\n

But let’s look at this more closely\u00a0\u2026<\/p>\n

<\/p>\n

 <\/p>\n

Manual flash<\/h2>\n

Firstly, flash could simply be\u00a0a consistent amount of light<\/strong> that is emitted from the flashgun.\u00a0 In the case of manual flash, there is NO control by the flashgun or camera, over the intensity or duration of the pulse of light from the flash unit.<\/p>\n

This is manual flash.\u00a0 Photographers can control the output of their flashguns by adjusting the settings in fractions of the maximum possible output, eg, \u00bc power, 1\/16th power.\u00a0\u00a0 It should be obvious that the absolute value of\u00a0\u00bc power will vary from flashgun to flash gun, as each model and make of flashgun has a different maximum power.\u00a0 Manual flash exposure is most easily measured by a handheld flashmeter.<\/p>\n

To re-iterate: with manual flash,\u00a0we<\/strong> have four controls for the flash exposure:<\/strong>
\n– the actual output level from the flashgun, (ie the ratio of full power),
\n– distance from our light source to the subject,
\n– aperture,
\n– ISO.<\/p>\n

Any of these four things can be used to control the amount of light falling on your subject.<\/p>\n

 <\/p>\n

TTL flash<\/h2>\n

The second way to control flash exposure, is as an automatically controlled burst of light<\/strong>. This flash output can either be controlled by the flashgun itself (usually called Auto mode), or by the camera in conjunction with the camera\u2019s metering system (usually called TTL flash).\u00a0 When the\u00a0flash is controlled by the camera, as then measured as the amount of light coming through the camera\u2019s lens, it is called Through-The-Lens flash metering, (hence, TTL flash.)<\/p>\n

For most purposes in understanding the basics of\u00a0flash exposure with D-SLRs, there is little difference between Auto flash and TTL flash.\u00a0 So, as mentioned earlier, for simplicity\u2019s sake here, we could\u00a0group Auto flash and TTL flash together.\u00a0 (There are differences with pre-digital cameras and older flashguns, in how Auto flashguns interface with the cameras, and then the explanation is slightly more complex.)<\/p>\n

Anyway, with TTL flash, the flash output is varied and controlled by the camera\u2019s metering system. This means that for a certain range, our chosen aperture or ISO, or distance to our subject, does not influence our TTL flash exposure<\/strong>.<\/p>\n

This is such a crucial point to understand about TTL flash, that I want to mention it again for emphasis.<\/p>\n

With TTL flash<\/strong>,\u00a0our chosen aperture or ISO (within a certain usable range), does not<\/strong> affect our flash exposure<\/strong> – and in a sense our aperture and ISO choice becomes transparent to our exposure metering. (Our camera and flash work together in calculating what it deems to be correct flash exposure, but increasing or decreasing the output from the flash.) \u00a0What does<\/em><\/strong> affect our TTL flash exposure, is the reflectivity of our subject, and how large our subject appears within our frame.<\/p>\n

In other words: \u00a0Aperture (and ISO) does not change flash exposure<\/strong> when we use TTL<\/a>. This is because the camera will tell the flash to emit more (or to emit less) light, as the camera deems necessary for correct exposure.<\/p>\n

This is something that is difficult to comprehend at first, but is easily verifiable with your D-SLR.\u00a0 There, at home, you can photograph any subject in your immediate surroundings using a TTL capable flashgun. Remember to\u00a0bounce your flash<\/a>\u00a0for best results indoors.<\/p>\n

Using TTL flash, you can change your aperture from f\/4 to f\/5.6 to f\/8 … and your flash exposures should look the same. Similarly if you changed your ISO, your TTL flash exposures should look the same. The reason for this is that your camera and flashgun’s TTL flash metering system takes care of the basic flash exposure … and can do this within a certain range of chosen apertures and ISO settings. Your flashgun will emit more or less light as required for correct exposure, dependent on your settings … but your flash exposures should appear similar.<\/p>\n

So, looking back at the four things which affect manual flash, you’ll notice that none of these, not distance, nor aperture, nor ISO setting, <\/strong>changes our TTL flash exposure. (Within reasonable range of course.)<\/p>\n

And it is in this, that we see the huge difference in using (and understanding) manual flash vs TTL flash metering.<\/p>\n

 <\/p>\n

\n

\n\t\t\t\t\t\"Direction<\/a>\n\t\t\t\t<\/div>
\n\t\t\t\t\t

Direction & Quality of Light<\/h2>\n

I tried to distill the essence of what we, as photographers, work with – light! Before we can truly grasp on-camera flash and off-camera flash, and really, any kind of photography, we have to be aware of the direction and quality of light. We need to observe the light that we have, and then decide how best to use it, or enhance it.<\/p>\n

With this book, I try my best to share those \u201caha!\u201d moments with you, and I do believe this book can make a difference to your photography.<\/p>\n

The book is available on\u00a0Amazon USA<\/strong><\/a>\u00a0and\u00a0Amazon UK<\/a><\/strong>, or can be ordered through Barnes & Nobles and other bookstores. The book\u00a0is also available on the Apple iBook Store, as well as Amazon Kindle.\n\t\t\t\t<\/div>

<\/div><\/p>\n
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 <\/p>\n

TTL flash vs manual flash<\/h2>\n

The only way to control TTL flash metering, is with flash exposure compensation<\/strong><\/a>. While you could could control manual flash exposure with any of the four variables mentioned earlier on, with TTL flash you would have to change your flash exposure compensation.<\/p>\n

In these differences,\u00a0the individual strengths of using manual flash, or using TTL flash, can be seen.\u00a0 And this\u00a0will most likely affect which of the two kinds of flash\u00a0lighting we end up using.<\/p>\n

With manual flash, since the flash is a specific level, our subject\u2019s reflectivity or our choice of composition (ie, how we frame our subject) has absolutely no impact on our metering.<\/p>\n

This is a hugely important aspect of manual flash.\u00a0 Once we have our lights set up at a specific distance, and determined our aperture and ISO … then the subject’s reflectivity (ie, how much lighter tones or darker tones there are), have NO effect on our flash exposure.<\/p>\n

However, with TTL flash, the subject’s reflectivity \/ tonality, and our choice of composition, WILL affect our flash exposure.\u00a0\u00a0 And hence, we often need to control our flash exposure with the flash exposure compensation.<\/p>\n

The concepts explained in this section\u00a0are so essential to our further understanding in flash photography, that I would strongly suggest re-reading this section until it makes sense.\u00a0 Also check\u00a0other webpages or books on this topic.\u00a0 It is also important to your own understanding of flash photography, to try and figure this\u00a0out with your own camera and flashgun.<\/p>\n

In\u00a0 thoroughly grasping\u00a0of\u00a0the differences between manual flash and TTL flash, our approach to balancing flash with available light<\/a> will become so much easier.<\/p>\n

 <\/p>\n

Related articles<\/h2>\n