![\"\"](\"https:\/\/neilvn.com\/tangents\/images\/flash\/ttl-flash-aperture.jpg\")
<\/p>\n<\/p>\n
The axioms\u00a0regarding flash photography that get thrown around most often, are:<\/p>\n
While these are true, there’s also an over-simplification happening here.\u00a0Just rallying those two statements in a perfunctory manner, we actually lose understanding of how flash and ambient exposures actually inter-relate.<\/p>\n
The problem with the first<\/em> statement is that it disregards that aperture and<\/strong> ISO both control ambient exposure as well.<\/p>\n The second statement – that flash exposure is controlled by aperture, falls down a bit on two counts: Where these short-cuts (or axioms)\u00a0came into being, is that with\u00a0flash<\/a><\/strong>, our exposure is controlled by 4 things<\/a>: ** The exception, or complication if you will, is that if you go to high-speed flash sync<\/a>, shutter speed becomes a linear control of the flash exposure. But we’ll leave that aside now, to focus on the explanation of how TTL flash and manual flash differ.<\/p>\n As explained in more detail in this article<\/a>\u00a0–\u00a0with manual flash, we<\/strong> control those four factors. With TTL flash, the camera<\/strong> changes the power as we change any of the other three variables. This means that the camera will adjust our flash exposure as we change those settings.<\/p>\n It is essential to understand this specific difference between\u00a0TTL flash and manual flash – it changes things a little. Actually, things change a lot, since how<\/strong> the exposure is controlled for manual flash and TTL flash are now entirely different.<\/p>\n This affects how<\/strong> we control our flash exposure – and this is where I feel the axiom that the simplified axiom that\u00a0“aperture controls flash exposure”, becomes\u00a0misleading.<\/p>\n <\/p>\n <\/p>\n Restating all this again – with TTL flash, your camera and flash work together to control\u00a0\/calculate\u00a0flash exposure … and then adjust the power the flash emits, to give you (what it deems to be) correct flash exposure … regardless of your choice of aperture, or your choice of ISO, or the distance of your flash to the subject.\u00a0 Of course, these things have to be within reason.\u00a0 You have to work within the capabilities of your flash.<\/p>\n Let’s see how this works.\u00a0 Here are two images that I used in my book on flash photography techniques<\/a>,\u00a0and I’d like to use them with a slightly different take.<\/p>\n With our model, Jackie, positioned in front of a window, we have two\u00a0things to expose\u00a0for: Ambient exposure <\/strong>for the background – shutter speed, aperture and ISO.\u00a0 Simple enough.<\/p>\n Flash<\/strong>\u00a0to\u00a0light our subject – the settings\u00a0will depend on whether we are using manual flash or TTL flash.<\/p>\n As mentioned, if I had used manual flash here (for example with a softbox), then I would have to meter my manual flash<\/a> for the specific aperture and ISO and distance and power setting of my flash. And then juggle those four things to give me correct exposure as metered with a flashmeter.<\/p>\n But in this case, I used TTL flash that I bounced over my left shoulder into the room.\u00a0And I purposely set out to use TTL flash here in a way to illustrate this\u00a0point: With TTL flash, aperture effectively becomes transparent.<\/p>\n In other words, with TTL flash, our choice of aperture, (within reason), has no effect on flash exposure.\u00a0 (This is also true for our choice of ISO.)<\/p>\n <\/p>\n For photographers who are familiar with manual flash, this distinction might seem of small importance – sure, TTL flash is an automatic metering of the flash. Seems simple enough.<\/p>\n Then let’s look at a scenario: You are using bounce flash<\/a> in TTL mode, because bounce flash easily gives you soft diffuse light .. and bounce flash is usually quicker in TTL mode as you move around the room.<\/p>\n Now, for some reason, your TTL flash exposure is suddenly incorrect. Let’s say the black evening dresses are throwing\u00a0off your TTL metering, causing your flash to over-expose.<\/p>\n Having memorized that “aperture controls flash”, you dial camera from f\/4 to f\/5.6 because that, according to How Things Work, is how you pull the flash exposure down. Except it doesn’t this time. It doesn’t work that way with TTL flash – because, with TTL flash, the aperture becomes “transparent” to the flash exposure.<\/p>\n Instead, you need to dial your Flash Exposure Compensation<\/a> (FEC), because that is now the way you control your flash exposure. Not the aperture. The FEC. It might seem a trivial distinction to some, but from experience, I know that this throws newer photographers entirely – they want to adjust the aperture, because that is what they’ve been taught.<\/p>\n In this way it becomes an important to fully understand how TTL flash and manual flash differ – and how to control either. You’ll be a stronger photographer if you’re able to handle either of those two flash modes unhesitatingly.<\/p>\n <\/p>\n Let’s look at my choice of exposure settings for those two images\u00a0–\u00a0traditionally, if we wanted our background darker while using flash to light our subject, we would change our shutter speed.\u00a0 Normally I too\u00a0would’ve changed my shutter speed from 1\/125th to 1\/250th before I would’ve made any changes to aperture or ISO.\u00a0 That would gain\u00a0me a stop already on my background exposure, without my flash having to work harder.\u00a0 It absolutely makes sense to change shutter speed first to change ambient exposure, before changing any other exposure control.<\/p>\n But in this example, I willfully went the other way.\u00a0 I kept my shutter speed constant .. and changed my aperture.<\/p>\n Now, if this had been manual flash, I would’ve had to change my ISO or bring up the power on my flash or bring the flash closer to my subject to compensate for the change in aperture.<\/p>\n But with TTL flash, the flash and camera calculated the exposure it thought I needed, and automatically compensated for the change in aperture.\u00a0 I did not have to change anything.\u00a0 My camera and flash did.\u00a0 I did have my flash exposure compensation set to +1.0 EV for every image in the extended sequence.<\/p>\n As I changed from f2.8 to f5.6 .. I could continue shooting and get the same (TTL) flash exposure. My camera and flash followed my change in settings seamlessly to give me exactly the same flash exposure at f5.6 as it had at f2.8<\/p>\n Sure, the flash had to work much harder.\u00a0 In fact, it had to dump 4x the amount of light at f5.6 as it had at f2.8 … but my exposure remains the same.\u00a0 And this is the reason why even with TTL flash, we’d rather change the shutter speed first to affect our ambient exposure .. even if we don’t “have to” like we would “have to”‘ with manual flash.<\/p>\n And as you can clearly see, in changing our aperture, our background exposure changed.<\/p>\n So back to those two axioms\u00a0about flash, but this time in regard to using TTL flash exposure as I had in this sequence.<\/p>\n <\/p>\n My sincere belief with this is that if we can completely understand how flash and ambient exposures inter-relate, we will … well, we will have exactly that .. complete understanding of how flash and ambient exposures inter-relate.<\/p>\n <\/p>\n When aperture doesn’t control the flash exposure The axioms\u00a0regarding flash photography that get thrown around most often, are: ambient exposure is controlled by shutter speed, flash exposure is controlled by aperture. While these are true, there’s also an over-simplification happening here.\u00a0Just rallying those two statements in a perfunctory manner, we actually lose understanding of how Read more inside…<\/a><\/p>\n","protected":false},"author":1,"featured_media":31888,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_monsterinsights_skip_tracking":false,"_monsterinsights_sitenote_active":false,"_monsterinsights_sitenote_note":"","_monsterinsights_sitenote_category":0,"_genesis_hide_title":false,"_genesis_hide_breadcrumbs":false,"_genesis_hide_singular_image":false,"_genesis_hide_footer_widgets":false,"_genesis_custom_body_class":"","_genesis_custom_post_class":"","_genesis_layout":"","footnotes":""},"categories":[14,15],"tags":[56,318],"yst_prominent_words":[5375,6041,9833,9830,9828,3715,9838,9836,8125,9834,9835,1416,9806,9832,1417,1198,1415,8124,2950,9840],"class_list":{"0":"post-1771","1":"post","2":"type-post","3":"status-publish","4":"format-standard","5":"has-post-thumbnail","7":"category-exposure-metering","8":"category-flash-photography","9":"tag-flash-photography-tips","10":"tag-ttl-flash-photography","11":"entry"},"_links":{"self":[{"href":"https:\/\/neilvn.com\/tangents\/wp-json\/wp\/v2\/posts\/1771"}],"collection":[{"href":"https:\/\/neilvn.com\/tangents\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/neilvn.com\/tangents\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/neilvn.com\/tangents\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/neilvn.com\/tangents\/wp-json\/wp\/v2\/comments?post=1771"}],"version-history":[{"count":9,"href":"https:\/\/neilvn.com\/tangents\/wp-json\/wp\/v2\/posts\/1771\/revisions"}],"predecessor-version":[{"id":49066,"href":"https:\/\/neilvn.com\/tangents\/wp-json\/wp\/v2\/posts\/1771\/revisions\/49066"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/neilvn.com\/tangents\/wp-json\/wp\/v2\/media\/31888"}],"wp:attachment":[{"href":"https:\/\/neilvn.com\/tangents\/wp-json\/wp\/v2\/media?parent=1771"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/neilvn.com\/tangents\/wp-json\/wp\/v2\/categories?post=1771"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/neilvn.com\/tangents\/wp-json\/wp\/v2\/tags?post=1771"},{"taxonomy":"yst_prominent_words","embeddable":true,"href":"https:\/\/neilvn.com\/tangents\/wp-json\/wp\/v2\/yst_prominent_words?post=1771"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}
\n–\u00a0\u00a0flash exposure is controlled by aperture \u2013 but only for manual flash<\/a>.
\n– \u00a0ISO also affects manual flash exposure.<\/p>\n
\n– aperture \/\u00a0ISO \/\u00a0distance (light source to subject) \/ power of our light.
\nThis leaves shutter speed<\/strong> as our only independent control for ambient light. **<\/p>\nWith TTL flash, aperture effectively becomes transparent<\/h2>\n
\n– we have the ambient exposure to consider for the outside background,
\n– and we have flash exposure to consider for our subject, Jackie,\u00a0who would be under-exposed if we didn’t add additional light.<\/p>\n<\/p>\nWhy this distinction is important<\/h2>\n
\nLet’s say you are photographing people at an event – it could be a bride during her preparation, or it could be guests at the cocktail hour of a corporate event. Same thought-process.<\/p>\nLooking at our exposure settings again<\/h2>\n
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Summary<\/h2>\n
Related articles<\/h2>\n
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