February 7, 2011

photography questions and answers

The past few days’ posts were all set to be part of the on-going question and answer theme where I look at search engine queries, and directly answer a selection of 10 questions. But they all  expanded into something longer that warranted individual posts:
available light vs fill-flash
best fill flash settings
exposure metering modes

Anyway, here is the usual instalment with 10 fairly random questions and answers:

01)  do I need to adjust my camera exposure with flash photography

Interestingly phrased – and the answer is, yes, to an extent. To an extent you don’t need to adjust your camera exposure when you use flash photography .. IF (and a big if) .. IF your ambient exposure is low enough.

With this wedding portrait, my camera settings were  1/50 @ f4.5 @ 800 ISO, using TTL bounce flash.

The flash entirely dominates. It is in effect the only light source here. Since my ambient light levels are so low, I could’ve had a whole range of combinations of camera settings, and the TTL flash would still have taken care of the exposure.

In that sense, I need not adjust my camera settings. I could take numerous photos, and the TTL flash technology would take care of my exposure.  It’s now just up to me to make sure my composition and timing and direction of light is good. So to a large extent, I could ignore my camera settings.  But this only works when the ambient light levels are low.  The moment the ambient light becomes more prominent .. eg, in brighter light, or because of my camera settings .. then I need to think more carefully about how to balance my flash with the available light.

This somehow segues into our next question, by way of contrast …

02)  flash output needed to overpower the sun

With manual flash, we have 4 controls for the flash exposure – aperture, ISO, power, distance. SInce the Sunny 16 rule tells us that we’re most likely in the region of: 1/250 @ f11 @ 100 ISO … this means we have to get f11 @ 100 ISO out of the flash, or more.  We only have the flash’s power and distance-to-the-subject to work with then to get that f11 @ 100 ISO (or there-abouts).  Since we’re probably working at full power anyway, or close to it … this then only leaves us the distance to work with.  In other words, you have to get the flash close enough to your subject to give you that f11 @ 100 ISO (or more).  So for us speedlight shooters working in bright sun, it is usually not so much the flash output per se, but rather the distance between the flash and the subject. Oh, and while we’re on that topic, going into High Speed Sync mode will not solve your problem, but will worsen it … unless you have plenty juice to spare in your speedlight. Taking your shutter speed over maximum flash sync speed into high-speed flash sync, means less flash power.

03)  aperture controls flash exposure

Sometimes I feel like Don Quixote, tilting at this particular windmill … but really, aperture only controls flash exposure with manual flash. For TTL flash, there is an entirely different process at work. We really need to differentiate between TTL flash and manual flash, since for TTL flash, aperture does not control the flash exposure. When you hear someone say, “aperture controls flash exposure”, you just need to add the mental asterisk there yourself … *only for manual flash.

04)  lens hoods, yes or no

Dude! Yes! Unequivocally and indubitably, the use of lens hoods are necessary. In fact, lens hoods should be mandatory.

05)  how to avoid shadows when using flash vertically

We can avoid that typical hard flash shadow, by bouncing our flash. Or using some kind of light modifier like an umbrella or softbox. But the method that is the most easily available to us indoors, is simple bounce flash.

If you do need to use flash directly, and need to shoot vertically, then your best option is a rotating flash bracket.

06)  why does TTL bounce flash need extra flash exposure compensation?

In theory, TTL flash exposure shouldn’t differ whether we shoot straight-on or with bounce flash. Keeping in mind that we need to stay within the range that the flash is capable of working in. Quite often we might be too close to our subjects when we shoot at a wider aperture.  (Check the scale on the back of your speedlight.)

In practice we could very well find that we need to bump up the FEC a notch or two when bouncing flash. I take it to just be “one of those things”. Camera make and models vary. The algorithms they use to calculate flash exposure, all vary. So we could very well find that somehow we need more FEC with bounce flash.  It’s one of those things we need to be aware of for our specific camera and flash, and then automatically adjust our settings for.

So why does TTL bounce flash need extra FEC some times? I don’t know. But I do know my cameras and adjust them accordingly, and get on with the photography.

07)  how do you exposure for your subject? skin tones two stops up

With the Zone System, Caucasian skin tones are usually placed at Zone VI / Zone 6 .. which is one stop up from middle grey / Zone V.  Very light skin tones might be placed at 2 stops up from middle grey. ie, Zone VII.  However, skin tones vary a lot, and we need to keep that in mind.

Now, applying the classic Zone System directly like this – placing skin tones by adding a stop more exposure – is something we could do with B&W photography where we have exact control over the choice of film, processing of the film, and the printing stage. For digital, metering off Caucasian skin tone, and then adding 1 stop more exposure, could very well lead to over-exposure.  Certainly, 2 stops up from a mid-tone with a digital camera would push the histogram right to the edge or beyond. Over-exposure.

Therefore, metering off skin tones is something we could do, but we’d have to evaluate how light or dark the skin tones is that we’re metering off.

That said, I do believe that an understanding (if not quite direct application) of the Zone System is essential in understanding exposure metering in photography.

08)  what is the flash power setting for off-camera flash without a softbox

It’s impossible to give a direct answer to this. It really depends on what your ambient light is doing, and what you are trying to achieve with flash.

That said, metering for off-camera flash is most easily done with a flash-meter. If you don’t have a flash-meter, then the flash’s Guide Number will tell you what you need to know. Or just look at the distance scale on the back of your flash.

Since manual flash is dependent on:
- aperture
- ISO
- distance of your flash from your subject
- power setting

… it means we need to adjust our flash’s power output for the chosen aperture /  ISO / distance combination. The distance scale on the back of the flash will tell us what we need to know  to get close to correct exposure for our manual flash.

I feel compelled to make screengrabs of some of these search engine queries, just in case people might think I am being cute and just making this stuff up:

09)  what is the best thing about camera companies

Well, for me, the best thing about camera companies, is that they make the toys we all love so much!

10)  And as always, the final one is a funny … by virtue of this blog’s name

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{ 12 comments. } Add a Comment

1 parv February 8, 2011 at 6:01 am

About lens hoods … some of the lens suppliers do not exactly make it hassle free to include a hood as a standard part of a lens (as available in retail). They should (have) just include(d) the damn hood & adjust the price accordingly.

Moreover, in gear packing|carrying discussions, some people invariably mention that they forgo the hood in lieu of other items. I think both of those factors may give the impression that a hood many not be a necessity.

About a decade ago, I had to order a hood separately for a Tokina lens (IIRC, hood delayed the delivery for being part of the same order). As far as I know, Canon still does not include a hood. Sony lenses do come with a hood. What is the situation with lenses from other companies?

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2 Stephen February 8, 2011 at 9:14 am

Parv,
Nikon includes lens hoods on some of its lenses. Nikon definitely includes hoods on professional-grade lenses, while they usually do not include a lens hood on some consumer-grade lenses (particularly the low-end lenses).

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3 parv February 8, 2011 at 10:03 am

Thank you Stephen. Your comment made me to look for the same in case of Canon, which seems to be true …

Canon EF-S 18-55mm f/3.5-5.6 IS
http://www.bhphotovideo.com/c/product/519475-USA/Canon_2042B002_EF_S_18_55mm_f_3_5_5_6_IS.html

Canon EF 70-200mm f/2.8L IS II USM
http://www.bhphotovideo.com/c/product/680103-USA/Canon_2751B002_EF_70_200mm_f_2_8L_IS.html

… I partially stand corrected.

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4 Dan Rode February 8, 2011 at 11:12 am

I never used “protective” filters but I always use a lens hood. I simply can’t think of a reason to not use a hood. My favorite hood is the metal screw-on hood on my 85mm f/1.8. A plastic hood would give more and thus provide a more impact protection but the non-petal style metal hood allows me to use 77mm cap on the end of the hood, so I never have to remove it or fumble around trying to attach a cap through the hood.

My little $100 50mm has a screw-on collapsible rubber hood that I picked up for $5 on ebay. Works great. I just fold it up, pop thew cap on and toss it in my bag.

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5 Stephen February 8, 2011 at 12:19 pm

In “flash output needed to overpower the sun,” everything Neil has said is true. However, there is one other option if you must use speedlights to overpower the sun and you end up in high speed sync mode. Neil has a blog entry here:

http://neilvn.com/tangents/2010/12/06/using-multiple-speedlights-with-high-speed-flash-sync/

Yes, you need multiple speedlights. One will not be enough for the reasons Neil stated. You are compensating for the loss of power of an individual speedlight in high speed sync mode by having multiple speedlights in high speed sync mode collectively produce the light needed. Joe McNally is famous for his crazy multiple speedlight setups.

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6 Neil vN February 8, 2011 at 3:07 pm

.. or, simpler yet than multiple speedlights, use a neutral density filter when you would otherwise have ended up in the higher shutter speed ranges.

Neil vN

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7 Russ February 8, 2011 at 8:23 pm

Last one is easy: tangent? = opposite/adjacent.

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8 Neil vN February 8, 2011 at 9:58 pm

Yup, it’s sad when your search for help with Math homework becomes a desperate plea for help on Google.

Neil vN

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9 Kevin Deibert February 10, 2011 at 2:19 pm

Neil,
I’m almost through reading your book “On Camera Flash” and the one thing that I have a question about is the FEC. In some settings your +.3 FEC, others +1 FEC, and even more…-1 FEC. So my question is…what do you use to determine the FEC value and are you only basing the FEC on a zeroed meter? The EV would only be adjusted to correct the tone of the scene based on ambient, right?
Best,
Kevin

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10 Neil vN February 12, 2011 at 4:11 am

Hi there Kevin ..

You can’t simply zero your camera’s meter.
which exposure metering mode
exposure metering techniques

Flash exposure compensation is adjusted according to:
– tonality of your subject,
– how much flash you actually want to add to the final image. Sometimes you want fill, sometimes you want flash to dominate … and sometimes you want something inbetween. Your choice .. which is also guided by the particular scenario you find yourself in.

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11 JohnG February 17, 2011 at 11:39 am

Neil,

Any inputs on when to use SB-900 illumination pattern mode ?.

TIA,

John

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12 Neil vN March 6, 2011 at 5:48 pm

John .. with the SB-900 I keep them to Standard illumination pattern.

I very rarely use direct unmodified flash as the main source of light. Indoors I usually bounce my flash, and on location I use softboxes and such. Therefore the actual illumination pattern doesn’t really matter.

I suppose that using Center-Weighted illumination pattern might give marginally stronger flash since it is more concentrated towards the middle of the area that the flash is pointing to. For simplicity though, I keep to the defaults on all my SB-900 units.

Neil vN

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