Some photography/camera basics and techniques

[Steve Foss]

This is the first in what I hope will be an ongoing discussion to help beginning photographers grasp basic photography facts and principles. Feel free to reply with added perspectives. I've stickied this post, so people will always know where to find it.

Please post your photography questions in this thread, and eventually this will become an excellent reference for any aspect of photography.

And thanks!

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First, a primer on iso/shutter speed/f-stop, in case you're not quite up on all that. These are crucial concepts to understand in order to alter the way you capture images to suit your desires.

Film or the sensor needs a certain amount of light to produce a properly exposed image. The lower the iso number, the more light is needed for that exposure. Also the lower the iso, the finer the appearance of the grain in the image. Most digital cameras do quite well up to iso400, but some camera sensors produce better quality at higher iso settings than others. At high iso, grain is a problem, as is a phenomenon called digital noise, which produces pixels with wild colors unrelated to those around them.

But whatever the iso, at that iso the sensor always needs the same amount of light to produce a proper exposure. And there are two ways to control how much light reaches the sensor/film and how long it takes to build the right amount of light. Shutter speed (a camera function) is measured in fractions of a second or in multiple seconds, and simply tells us how long the shutter is open and allowing light to reach the sensor/film. F-stop (a lens function), is expressed in f values such as f2.8, f8, f22, and tells us how wide the lens aperature is open during the opening of the camera shutter. The lower the f-stop value, the wider open the aperature and the more light that can come through it.

A key here is that f-stop and shutter speed are two interlocking aspects. A properly exposed image requires a certain amount of light striking the sensor. If you slow down your shutter speed, your shutter stays open longer, but to compensate for that and make sure the image is exposed right, your camera automatically narrows the aperature opening. So your shutter is open longer but the lens allows less light through. The two work together, you see, for a properly exposed image.

The two most important things to remember about aperature and shutter speed are that aperature also controls depth of field (depth of what’s in focus in the frame) and shutter speed controls motion.

The faster the shutter speed, the more likely you’ll be able to freeze motion within the frame, because there’s a lot less relative motion captured at a tiny 1/2000 of a second than there is when the shutter’s open for 1/2 a second.

The wider open the aperature, the shallower the depth of focus and the easier it becomes to isolate a subject from foreground/background elements. And here’s a caveat. Powerful telephotos have inherently shallower DOF than wide angles. So, for example, at an f4 aperature, a 400mm lens may have a DOF of three inches, and a 22mm a DOF of three feet.

So let’s have an example of how these three elements work together. You’re shooting pictures of a bird in relatively low light. You’re using a telephoto that opens to f5.6, which is not particularly wide. The birds moves quickly, and you want the image sharp. You’re at iso200, and the best your camera will allow with the aperature wide open at f5.6 is a shutter speed of 1/60 of a second. And you can’t get a sharp image of the bird at that shutter speed because the shutter’s open too long and there’s too much motion, both from the bird and from your hand shake. You can eliminate hand shake by using a tripod, but even then it’s probably not going to be a fast enough shutter speed. What do you do? Bump up your iso to 400, that’s what! That iso reading tells you less light is needed to properly expose an image than an iso of 200, and that your camera shutter can be open less time at f5.6 than it could at iso200. So then you have a shutter speed of 1/125 or so, which makes it more possible to freeze motion. If that still doesn’t work, you can bump iso to 800, which may give you a shutter speed about 1/250, just as a general example, and give you a sharp image. But then, at iso800 and above, you have more worries about grain and digital noise. It’s better to get a sharp shot at a higher iso than a blurry one at a lower iso, and there are sophisiticated and easy to use programs these days to kill noise and grain.

When I’m out and about and don’t know what I’m going to run into, I set my camera to automatic aperature mode, set the lens aperature wide open (which allows the fastest possible shutter speed) and set my iso to 400. That means the aperature is fixed, and the camera will evaluate shutter speed based on available light and iso setting. If I find I can’t get a fast enough shutter speed for the subject I encounter, I bump up iso. But that rarely happens. At any rate, this automatic setting lets me get the best images of fast-moving situations, in which I don’t have time to make manual adjustments.

My Canon 20D, in “auto everything” mode, doesn’t open the lens aperature to maximum, but compromises by lowering shutter speed a bit and narrowing aperature a bit. A sort of “middle of the road” approach that most full automatic modes produce. This is fine in many situations, but if your camera does the same thing as mine in that mode, you’ve cheated yourself a bit on shutter speed, because maybe you could have gotten a little extra shutter speed and frozen that first bird if your lens aperature was as wide open as possible. That’s why I set mine to aperature priority — it gives me as much shutter speed as possible.

Resolution:

At the low resolutions required for computer screen viewing (72-96 dpi), you don’t need a camera with lots of megapixels. When you size a 2 Mp image down to 700x500 pixels at 96 pixels per inch (general max resolution for some computer screens), you’re throwing away unneeded pixels to get there. The higher the camera’s Mp count, the more you’re throwing away to get to that low resolution. It’s when you go in for printing and enlargements at the 300dpi standard for photo printing and glossy magazines that you need more. Nice little 4x6 prints can be handled easily by a 2 Mp camera if you don’t have to crop much. Nikon’s entry level DSLR has 6.1 Mp, Canon’s 8 Mp, and those are plenty to make very large prints. Most all-in-ones these days are 5 to 8 Mp, and they will work quite well for enlargements, though all-in-one sensors tend to be smaller than DSLR sensors and have more issues with digital noise at medium to high iso settings than DSLRs.

[Dbl]

Nicely done Steve.

[island guy]

Steve

I agree, nice job explaining.

Wish I would of seen this post two weeks ago. I've been going out at sunset with a friend to experiment with settings for a sunset shot. Using the digital, mostly on auto mode, has been going well.

What stumps us is a older high end canon SLR film camera he has. We've not tinkered too much with it, but can't seem to get the results we want. It is a fully manual camera. We use a tripod with 400 ASA film. On a sunset shot can you give any advice or recommendations on setting speed and f stop?? Is there a "rule of thumb" to follow?

Thanks!

[Steve Foss]

Hey IG:

No real rule of thumb. Even though it's a manual camera, it should still have a built-in light meter. Let that tell you where to establish your settings. Since you have a tripod, I'd go with a narrower aperature (higher f-stop number) to make sure you have the whole scene in focus. That will drop your shutter speed very low and, even with a tripod, you may want to use the camera's timer feature or use a remote shutter switch so there's no shake from your hand.

If it does not have a built in light meter, you'll have to buy a light meter for best results. Otherwise, if it has no meter and you have no light meter, bring the digital along, check what your auto digital reads in the same situation, duplicate the iso and aperature and shutter speed settings on the SLR and shoot. Then I'd make sure to bracket those settings, taking those settings as the mid point and taking several images from a full two stops underexposed to a full two stops overexposed. Make sure you jot down the settings for each frame for future reference.

Since you'll be shooting from a tripod, you may opt for iso200 or 100 film which will make enlargements with less grain than 400.

[huntmdown]

Steve,

Well done! The examples/comparisons provided association without getting to technical for easy reading! cool:

[island guy]

Steve

I took your advice on the film shots of sunsets. Worked out well. I do have a question on film speed. You recommended trying 200 or 100ASA to prevent grainy enlargements. What is the thought behind that? I just always assumed the higher the ASA the better my picture would look. I didn't base that on any fact it's just what I thought.

A group of us purchased a bunch of darkroom equipment for next to nothing at an estate sale and are having a blast goofing around with it. We all also have digital SLR and it is fun to compare film and digital. We had all chipped in on a high end printer so it cuts the cost for all of us on the digital printing. Nice way to go if you have a bunch of camera buddies and not much cash flow.

[Steve Foss]

Hey i.g.:

That darkroom work is a blast. I spent a few years in a B&W darkroom back in the 90s, and it was great fun.

The lower the ASA/ISO number, the finer the grain of the film. The finer the film grain, the finer the grain of the enlarged print, and the larger you ultimately can make the prints before the graininess overtakes the details.

I'm fully digital now, but I've made enlargements of Velvia (ISO 50) slide film to 30 inches across. Those were slides scanned on a top-end slide/negative scanner and printed as digital images with a top-end inkjet printer. They are rich and full of detail. But then, it's hard to find film with finer grain than Velvia 50.

Low ASA/ISO films also are "slower," because the lower the number, the longer the period that light has to hit the film to expose it properly. So they can be great for landscape work, where there's very little movement of the subject, but they demand very fast telephoto lenses (lenses that open to wide f-stops such as f2.8 or wider), tripods and excellent technique when shooting wildlife with them, because slow film means slower shutter speeds, and slower shutter speeds (the shutter is open longer) mean camera/hand shake and subject movement can easily blur an image.

[tjm]

I could use some help steve.

When i zoom in all my pics turn out like this

Anything i can do to try and fix my problem or no?

Otherwise it takes great pics

[Steve Foss]

Zoom in? Do you mean when you use the zoom feature on your camera, or when you crop and enlarge the image on your computer? If it's the camera zoom, some all-in-ones drop to a lower resolution when you use the zoom feature. If it's when you crop on the computer, your camera isn't set at a high enough resolution, or doesn't have high enough resolution, to support that much cropping and enlargement. It's also possible that you don't have your settings right in your photo processing program, and that, when you crop the photo and enlarge it, you're asking it to do something it can't do well.

So you'll have to tell me more in order for me to know what the specific problem is. What's the megapixel count for your camera, and what exactly do you mean when you say "zoom in?"

[tjm]

The cameras HP photosmart M517

5.2mp

24x total zoom

3x optical

8x digital

[Steve Foss]

Thanks tjm. We've established the camera has plenty of megapixel power to crop and zoom without pixelating like your image shows. Now, what do you mean by "zoom in?" Do you mean you're using the camera's max zoom power? If you are, check your camera's manual to see if that power automatically drops to a lower resolution as some do. If so, that's likely your problem. But whether it does or not, it's also possible that if you crop and enlarge on the computer, you're telling the image to remain bigger than it should be, which also causes pixelization.

And image is made up of pixels. The number of pixels in an image is determined by the resolution capability of the camera and by what it's set at. To get best results in image quality, make sure the camera is set at its maximum resolution.

After you download the pic, if you want to crop and enlarge, set the resolution to 96 dpi, which is the highest most computer monitors are capably of, and make sure that, when you set resolution, you check the box that allows the picture to resize itself to compensate. This is done somewhat differently depending on which pp program you use, but most allow you to set the resolution before you use the crop tool.

[sparkyaber]

Anyone have any good suggestions for a book that would assist someone just getting started in photography? I purchaced a Nikon D50 with a 18-55 lens for my wife and she would like to learn the basics. I do think a telephoto lens is in our future, any suggestions on that one also?

Does somebody make a "photography for Dummies" that is what we are dealing with here.

Also any other suggestions for beginners? My wife really doesn't have any hobbies, so I hope she will stick with it and enjoy it.

Thanks a bunch.

[yakfisher]

I am kinda of in the same situation, I just got a new Nikon D50 as well, and I haven't done much photography since a class I took in high school.

I picked up a book from National Geographic called; The Ultimate Field Guide to Photography. I have found it to be very helpful for me. Good luck finding a book.