Why does the quality of my pictures lower the more I zoom in?

Question

I have a Canon 60D with the 18-200mm kit Lens.

I was at the beach not too long ago, I took some pics of my son in the sand, from a very close distance and they came out great. Picture quality was top notch.

Same day, same location, same lighting, I took some pics of a hawk-like (not sure what it was) bird landing in a giant nest. I took several. They all look fuzzy, noisy; just not great.

The only difference here was I switched from auto setting to the setting with the running-man icon, and I was zoomed in all the way. I did not use manual settings because I am not experienced enough yet.

A couple nights ago I was trying to photograph the moon coming up over some hilltops. It looked great to my eyes, I tried taking pics of it (zoomed in all the way). I could not capture it the way my eye saw it. I tried with a wide aperture, small aperture, fast shutter, slow shutter. In all cases, if the moon looked right, the surroundings where too dark and you could just see the moon. If the surroundings looked right, then the moon was too bright and washed out. All of them were fuzzy too (not extremly fuzzy, but not sharp either), I did not use a tripod though.

Is this because I am just too inexperienced, or is this the limitations of my lens? If its me.. what can I do? if its my lens, what is it about my lens.. what should I look for in a new lens?

Answer 1

Typically, the rule is 1/focal length seconds of shutter speed for getting sharp pictures with stationary targets. So if you're shooting at 100mm, try to get at least 1/100th of a second in shutter speed. 50mm = 1/50th of a second. So if you're below that and there's no kind of image stabilization either get a tripod, monopod, brace yourself, or set the camera on something to get sharper pictures.

Also, with that lens, your aperture slows down as you zoom in if you're wide open. You literally can't shoot as fast on the long end as on the wide end.

For action shots, try between 1/320th of a second and 1/500th of a second shutter speed to freeze a lot of the action.

You can stop your lens down a bit to increase sharpness, but you'll need to raise your ISO to account for the drop in light to keep the same shutter speed. This may or may not be the source of your problems. Usually, image quality problems from wide open apertures are described more as 'soft' rather than 'fuzzy'. 'Fuzzy' is often the lack of high enough shutter speed and hand holding.

To take a decent picture of the moon, you're going to need a lot longer focal length, a tripod, and a fairly fast shutter. You can do it handheld, but not normally nearly as sharp.

In general, tripods are a decent investment when using longer focal lengths if you don't have good image stabilization or good high ISO (and a lot of times even then).

Answer 2

Kit lens are always worse than more expensive lens, but I don't really think this is the problem you're dealing with.

The first thing you should realise, if you don't know this yet, is that with a long focal length, even the small movement of your camera causes the picture move really fast, therefore you need a fast shutter (I'd recommend 1/500 and faster) to get a picture with no motion blur.

Another thing is that when you're photographing a subject in a distance and the air isn't very clear, there is a long path between your camera and the subject, therefore there is a lot of dust/fog/whatever else in your path and that may cause the final picture to be foggy, as you described it.

The last thing that comes to my mind is that you should try setting your aperture to something a big slower than the limit of your lens. If possible, don't shoot at f/5.6, but rather at f/8, maybe a bit slower. This will make the lens produce a better picture, although it will lose you some light, which you need to get a fast shutter, therefore this is a very difficult equation to count properly.

Answer 3

A good support for your camera is essential for getting sharp photos from a tele lens in low light. Use a sturdy tripod.

Any lens will reach its maximum sharpness with its aperture stopped down a stop or two. Especially a big range zoom lens like your in its extreme zoom. Try using aperture around f/11. This will set you up for quite a slow shutter speed, so again, use a tripod.

The exposure is hard to choose because moon is lit by sun, while the rest of the sky is not - luminosity is very different and exceeds any camera's dynamic range. Try shooting a little after sunset (or a little before sunrise) when the difference is only a couple of stops. And remember to bring a tripod.

Answer 4

There are several things happning that are probably all contributing to the reduced image quality:

• When you zoom in, the camera will pick a shorter exposure time to avoid motion blur. At 18 mm you can use times as long as 1/18 s., but at 200 mm you need 1/200 s. or shorter. If the camera can't fully compensate for the shorter exposure time, you get motion blur.
• The "running man" action mode will cause the camera to try to get even shorter exposure times in order to freeze the image.
• To get more light in to compensate for the shorter exposure time, the aperture will be opened as much as possible. The lens gives the best result with a smaller aperture, so this will reduce the sharpness of the images somewhat.
• The camera will pick a higher ISO setting to reduce the need for light, but this will also increase the image noise.

Answer 5

Some of it may be the lens (the 18-200 does have some image quality compromises to encompass the 10x zoom range), but there's also technique to consider.

The longer a lens is, the faster the shutter speed you need to mitigate camera shake blur, because the lens is physically longer, but also because it will magnify the shake more. The rule of thumb of 1/focal_length or faster (i.e., if you're @200mm, then 1/200s is a good guesstimate for "safe" shutter speeds with good handholding technique). Some would say this is not sufficient with higher-resolution sensors, and they multiply by 2 or throw in the crop factor as well. IS (which the 18-200 has) can help mitigate this requirement to a slower shutter speed, but you also need to watch your handholding technique.

With the picture of the hawk, when you switched to the "Sports" scene mode (running man icon), you basically told the camera to emphasize getting a faster shutter speed over other considerations. The lens was probably @200mm, and wide open at f/5.6 (a place where the lens will be at its softest), and with a high ISO (noise). Stopping the lens down to f/8 would have helped improve sharpness, but you probably required the high ISO setting to overcome the camera shake—even with IS in the lens. And if you were trying to track the bird across the sky, the camera was moving, which may have added to blur. And then there's misfocus...birds in flight are a difficult subject that require a great deal of practice and typically a 400mm or longer USM lens to get a great shot. The 18-200 does not have USM in it, so its autofocusing is a little slower, and that can mean all the difference between getting a bird in flight in focus or not.

With the moon, however, the lens is not your problem. As you noted, the dynamic range is very high. The moon is directly lit by the sun. Everything else is in the dark. The only way to get a moon with detail not lost into highlights in a scene with details not lost in shadow is to use separate shots at different exposure settings and combine them—either with HDR, exposure fusing, or masks and layers.

Answer 6

Although it came out several years after this question was asked, Roger Cicala, the founder and lens guru at lensrentals.com, codified in this blog entry what many of us already knew more or less intuitively from years of experience: Painting Zoom Lenses with a Broad Brush – Roger’s Law of Wide Zoom Relativity.

Through testing of a large number of copies of a large number of different models of zoom lenses Roger found that most zooms, particularly those with a fairly wide angle of view at their shortest focal length, tend to be sharpest at the widest/shortest focal length and less sharp at the longest/narrower end.

This is just one more factor that conspires against us when we shoot at longer focal lengths with zoom lenses, which also amplify the same camera movement more at longer focal lengths, and many times also have narrower minimum apertures at the longest focal lengths.

As others have already said, this paints us into a tighter corner where the narrower aperture combined with the need for a shorter shutter time require us to use a higher ISO to compensate for a lower exposure which adds the detail destroying effect of noise to the softer end of the lens.