Sunday, November 7, 2010

Photography Q&A - Volume 001

I've been so busy lately with various things around the home that I've been neglecting my videos somewhat. The next episode should be a quick Q&A one, but after putting some good though into the answers to the questions, which were submitted through my Binary Graphite profile on Facebook, I came to the conclusion I could better reply to them here. Winging the video would yield short answers with little sustenance, and in the end I'd still end up writing a supplemental blog post. At least with writing I can take my time to better conjure up an adequate response. So let's get started!

Oh, but before I do, a quick word of warning. Some of the questions/answers below involve taking photos of the sun. If you do choose to take such shots, be warned that if you're not careful, you might not only cause irreparable damage to your camera, but to your eyes as well.

Question 1: What is the best way to use a lens hood? Once again, I tried to use one for a picture of a sunset but there was still a noticeable flare.

Answer 1: First of all, let me quickly talk about the purpose of a lens hood. For one, they are primarily designed to cut down extraneous light entering lens, which often has the effect of producing flare on the photo. Another way to understand this is that lenses are designed to take in light ideally coming from only particular angles, and if you try to visual this, think of a squashed pyramid of light going into the lens with the lens sitting at the tip of the pyramid. Still a little confused how that would look? No problem. After a little research I found a great link on the topic; the first one in the Web Resources section.

Hoods also offer some protection for the lens, especially the front element. Think about the time where you might have bumped your lens into a glass window; I know I've done that a few times at the zoo for example. But since I almost always have a hood attached to whatever lens I use, the plastic or metal shield easily handles the impact. Now to be clear, a hood does not make the lens invincible. Dropping your expensive piece of glass or giving it a heavy hit could cause damage to those fine components within the lens.

There are also a variety of lens hoods on the market. Often times, one will come with your lens, but they can also be purchased separately, to for example, replace one that has been damaged or went missing. Commonly, there are two major types: the petal and conical. I'm not going to rehash what is written in that excellent article mentioned earlier, but in a nutshell the petal design is generally more effective at blocking light rays that do nothing or are no good for photos verses the conical design hoods. Other reasons for purchasing a lens hood can include that you might already have a conical one but would rather go for a petal design to help further reduce chances of flare, or perhaps the existing hood is too shiny on the inside and one with a higher quality matte finish may improve the situation.

Now let's start addressing the question. In some cases, flaring might still occur even with a lens hood attached; simply said, they are not foolproof devices. When shooting photos of sunrises or sunsets with the sun framed within the image, a lens hood is next to useless (perhaps they help a little if there are other sources of light just outside the field of view of the lens; think street lights). Internal reflections (light bouncing between the lens elements and other internal components) often cause lens flares to occur. Some photographers like the effect, others don't; I personally don't mind, but it depends on the photo I happen to be taking. Now because I have not seen the photo from the person who submitted the question, perhaps I should have asked to see it, I have to generalize my comments a little. Since the sun is quite bright, even when nearing the horizon, there's not much one can do to completely eliminate flaring. Some lenses do handle it better, whether due to being prime lenses which are less susceptible to the effect or because they have high quality anti-reflective coatings (see that purplie-greenie hue on the lens?), or sometimes one can just luck out by being in such a position where the flare is barely visible.

My recommendation is to use a lens hood if you have one. It may not prevent flaring completely, but in many cases it will which can help improve your photos.

Question 2: I am still curious about multiple exposures.

Answer 2: I've been asked this question a while ago, but only now have I finally had the time to answer it (hence the "still curious" part). Stated simply, a multiple exposure is when two or more photos are taken to create a single photograph. In the days of film, there used to be some "magic" to this. To begin, you would take your first exposure and image would be physically there on the film. Then you would take the next exposure and of course the film would be exposed further, thus achieving some interesting effects.

However, taking multiple exposures using digital cameras is an interesting case. Many digital SLRs don't have the feature to perform such a thing, and those that do are limited to two photos (to the best of my knowledge I don't know of any that can do three or more exposures). So assuming the dSLR has a multiple exposure feature, you take your first shot like you would with film, but once the sensor has been exposed that image vanishes from the imaging chip. So where does the picture go? Well, right onto your memory card (or other storage medium). Here's where I feel the "magic" is lost. When you take the next exposure, and often the LCD screen will overlay the first image so you can compose the next photo more easily, the second exposure is again stored in memory and the brains of the camera combines the two shots into one. Yeay.

Really, a photographer could simply take as many photos as s/he wants and use an image editor like Photoshop to combine the images as s/he pleases. Frankly, I believe this option is open to far more creativity than being at the mercy of whatever capabilities the dSLR has.

Honestly, I've personally never been much of a fan of multiple exposure type shots, but there are a few that have caught my eye. In the Web Resources section below there is a link to an article on Shutterbug's website about this; I have to admit, I really like that dreamy appearance to the focus shifted shots.

Question 3: How do you take a picture of a sunset where the sun looks solid with sharp edges. Everything I have tried so far has yielded in a blurry blob of light (I am using a 50 mm lens with f16, high shutter speed and negative compensation).

Answer 3: Here again I should have asked to see some shots so I could target my response, but I do have some general pieces of advice to give. First off, as most people have already noticed, the sun is really, really bright, especially when it is high up in the sky. In cases like this, I actually don't recommend taking photos with the sun in the frame, especially with a telephoto lens (I would say anything greater than around 70mm). Remember when you used to be a kid and you could burn paper using a magnifying lens to focus the sun's light? Well, basically the same thing happens, but instead of being on paper, that bright spec of light is focused right onto your expensive sensor when you take a photo. And if you use the optical viewfinder, then keep in mind that the sun's light will be focused quite nicely onto your eyeball... it may be the last thing you see. Not cool.

Now does this mean you should never take a photo of the sun? Of course not. If the sun is very low to the horizon (sunrise/sunset) or if you're using a very wide angle lens, then usually this is not an issue. With the sun hanging low (below about 20 degrees), the earth's atmosphere filters out a lot of the sun's energy, in which case it's usually safer to use telephoto lenses. In addition, here's where an ND filter would come in handy, as that could further reduce the amount of light getting into the lens. And if the sun is above you head, then very wide angle lenses (less than 28mm), are generally ok to use; the sun is so tiny on the sensor that it lacks the energy to do much or any damage. But I will strongly recommend that if you are taking photos with the sun within your frame, make it quick, just to be on the safe side.

Back to the question. A few things come to mind as to why the sun appears as a blob versus a nice round circle with a hard edge. To start with and if you think this might be an issue, you could try manually focusing as on occasion the auto-focus system may not jive with the bright ball of mostly hydrogen in the frame. Next, using a 50mm lens means the sun will actually be quite tiny in the picture, and with the amount of glare around the sun, it may be challenging to get the sun to look hard edged. Thus, try shooting with a longer lens, like 100mm or greater (again, be careful and ensure the sun is nice and low to the horizon). Personally, nothing negative comes to my mind about using f/16, but you could open up the aperture to reduce the effects of diffraction. If you're not doing so already, I would also recommend shooting in manual mode, which will give you the ability to use whatever shutter speed you want. By the way, use a low ISO setting too (like 100); not only will this give you a cleaner image in terms of noise, but you may not need to use such fast shutter speeds as you would at higher ISO levels. The last thing that comes to mind at the moment is that perhaps the shutter speed was still to slow; depending on lighting conditions, the shutter speed might have to be around 1/1000 to 1/4000 of a second.

Lastly, I just want to add that if you are interested in solar photography (to clarify, that's taking photos of nothing but the sun --things like sun spots and prominences; not scenic landscape type photos), that's quite a different area and often involves getting very special filters (e.g. Baader solar filter) to block out as much as 99.9% of the sun's light and to capture specific wavelengths of light (e.g. H-Alpha). Also, this usually involves telescopes and very high magnifications of the sun, which again can permanently damage equipment and cause serious eye injuries and even blindness. If you don't know what you're doing here, don't try it.

Question 4: A little education on ND filters would be very appreciated.

Answer 4: Now I've already responded to this individual, but I thought I'd post my reply here as well. Episode 11 of my photography series is dedicated to the topic of neutral density filters, so for those of you also interested in finding out more about them, then by all means feel free to view the video. Now I've been meaning to do a show which discusses graduated ND filters specifically, but I have yet to find the time to work on it. Nonetheless, using graduated ND filters isn't very difficult and many issues related to "ordinary" ND filters apply such as quality of the material they are made from, color cast they might add to a photo, and how dark it is... well, how dark one half of the filter is.

Hopefully I've answered these questions well and they are helpful. As time permits, which has not been kind to me lately, I endeavor to finish that episode on taking photos of fast moving subjects. L8r!

Web Resources

http://toothwalker.org/optics/lenshood.html - Lens hoods
http://www.cambridgeincolour.com/tutorials/lens-flare.htm - Lens hoods and flare
http://shutterbug.com/techniques/pro_techniques/0408multiex/ - Multiple exposures

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