question for steve-

[MARINERMAGNUM]

steve i was wondering if you could elaborate on the exposure,shutter speed,iso,etc. and when to adjust these manually,under what circumstances as far as lighting should this be done manually. some birds won't give me the chance to make one setting before they fly off,so i have to use the camera's auto everything mode. also,will a 2,3,4,5,or 6 megapixel picture be any more clear than a 1 megapixel pic. if you re-size it down to 700x500 anyway? 2ndly-please tell me what i can do to improve my images-and please,be as brutally honest as you can. for instance,i took these 2 pics. today of a wren. both were done with the camera in "auto everything" mode. by using the manual adjustments,how could i have made the pics. look better? i know the 1st one is a little grainy from being a 640x480. but i really would have liked the 2nd one to turn out better. the more critical you are,the more it will help me. thanks!

[Steve Foss]

MM:

To reply in great detail to all your points would nearly involve writing a basic guide to photography.

But here goes.

First, a primer on iso/shutter speed/f-stop, in case you're not quite up on all that.

Film or the sensor needs a certain amount of light to produce a properly exposed image. The lower the iso, 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 whateve r 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.

MM, your first wren image is a little soft, but without your posting iso/shutter speed/f-stop data and what lens and camera you were using, I can only guess that your shutter speed wasn’t fast enough to eliminate hand shake and subject motion. Your second wren is sharper, nicely sharp. Both are very nice compositions, and they are far enough from the background that the background is rendered as a blur, which focuses the eye on your portrait. You may not have been able to make your pics look any better in a different camera mode. However, 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. But I don’t know whether your camera does what mine does on fully automatic or if you even have an aperature priority mode. If you have an “all-in-one” with a zoom, you may or not be able to change aperature. If you have a DSLR, it’s no problem. If you're not already, you'll need to become very familiar with your camera's owner's manual. It is your best friend when it comes to finding out what your camera can and can't do.

I don’t know what you think is wrong with the second image. It’s a very nice action shot of a wren in full song. The only thing I don’t like about it is that the sun is very high in the sky, which shadows part of the face of the bird. With portraits like that, you generally want light at a much lower angle, which tends to be gentler light because it’s more filtered through the atmosphere near the horizon and provides a nice even exposure. I also prefer not to shoot birds on feeders and nesting boxes, because I don’t like man-made elements in my nature photography, generally.That’s an individual preference, however, and one way is no more right or wrong than another in that aspect. Anchoring a branch or other natural perch near a box or feeder will tend to draw birds to the branch while they eye the box or feeder before moving in, and that’s what I usually do.

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.

Whew! There's much more to write about any and all of these factors, but that's the basics.

[buzzsaw]

Steve, I could have been more detailed than that explanation, way to short change the poor guy.

[Steve Foss]

He wanted it, he got it . . . Toyota.

[buzzsaw]

I was impressed and read it all slowly... I also shoot in AP mode but use the ISO auto function on my camera... I hadn't really thought about just setting it manually as it seems to do a decent job in the ISO auto mode. I may have to mess around and do some comparisons as all camera's are different. Time to ramp up for some Muskie fishing this weekend.... I hope to get some more fish pics.

[Dbl]

You know Steve that was such a good explaination, nothing less expected from a writer/editor/photographer, you may want to consider posting that as a sticky to help folks new to cameras.

[Steve Foss]

You know, I did think of that, but haven't had the time. I'll get to it, tho. Thanks, Dbl.

[MARINERMAGNUM]

thanks for all the info. i will try the things you said and post my results. thanks again!!