I have noticed what seems to be dust that i feel is on the inside of my lens,when i am at different focal lengths and certain shoting mode I see small orbs on the lcd screen and they also show up on the picture. i tried to shoot compressed air into the camera and they seem to have moved some .Is there any way of getting the camera open safely to cleen it better. What might be your suggestion??

Front and back focus tests are good to run. You need to do it for each prime lens (fixed focal length) you have, and at your favorite focal lengths for wide angle zoom lenses too. That means on this 17-50, you would pick wide 17mm and zoomed in 50mm, and several others between. If you pick 25mm and 35mm to test, you would end up with 4 potentially different adjustments. These would apply only at 17, 25, 35 & 50mm. If you shoot at say 20mm focal length, and assume it's the same as 17 or even 25mm, you may be wrong. Too much back or forward focusing is a problem with the camera body usually - not the lens.

I'd pay attention to the lens. Look for cloudiness on the edges of the glass, scratches and fungus on glass, wetness or oil on the aperture blades, specs of dust inside the lens, etc. All of these things take away value from the lens, as they can adversely affect the image or shorten the useful life of the lens. You check these things by looking directly through the lens (not on the camera) and look at a dark background - then a light colored background to help show dirt and dust inside.

The only other thing is to look at actual images taken with the lens. Enlarge the pictures to 100% or more. Look for fuzzy edges, purple fringe edges, colors. You will see all of these issues the more you zoom in. You have to decide what it acceptable to you and what is not. Expensive lenses capture great color, are very sharp and have minimal purple fringing on hard edges (high contrast areas) in pictures.

Good luck!

You're trying for what's called a narrow depth-of-field (DoF).

DoF is controlled by three factors: the aperture of the lens, distance to the subject, and the focal length of the lens. This has nothing to do with any particular design, it's simply physics.

The wider the aperture (smaller the f/number), the narrower the DoF. The A1200 does not have an Av mode which would let you control the aperture directly. However, it does have a Portrait mode, which is supposed to give you a wider aperture.

The closer you are to the subject, the narrower the DoF. This suggests that you get as close to the subject as practicable. However, in general you don't want to get too close for portraits as this tends to exaggerate certain facial features, like making noses look bigger.

The longer the focal length of the lens, the narrower the DoF. This suggests that you back away and zoom in. Yes, this conflicts with the previous paragraph.

Unfortunately, it's the actual focal length of the lens that matters here, not the "35mm equivalent" often quoted in the spces. The lens on the A1200 zooms from 5mm to 20mm. Landscape photographers like to use 24mm lenses on their 35mm cameras because that gives them practically infinite depth-of-field, from the flower in the foreground to the mountains in the background. The lens on your camera is shorter than that, so you're going to have a hard time blurring portrait backgrounds.

The best I can recommend is to put the camera into Portrait mode, put as much distance as possible between the subject and the background, get as close to the subject as possible, and zoom in to the longest focal length you have (remembering that the last two are in conflict).

You'll notice that the maximum aperture is specified as f/2.8-4.0. The lens has a maximum aperture of f/2.8 only at the 17mm focal length. At the 35mm focal length, the maximum aperture is f/4.

Does the lens open up to f/2.8 when you zoom out to 17mm?

HI, Just try adjust your focus in tele and macro modes to get the best focal length and make shoot to check the result. If it still show blur, seems you have lens in defective or controller problem inside the camera. Unfortunately it is hard to repair the lens and its driver by yourself. You've advised to get it repaired at dealer.

Regards,
Jay

You're trying for what's called a narrow depth of field. DoF is controlled by three factors: distance from camera to subject, lens focal length, and lens aperture. The closer the camera is to the subject, the narrower the DoF. The longer the lens focal length, the narrower the DoF. The larger the lens aperture, the narrower the DoF.

Get as close to the subject as practical, and use as long a focal length as practical. I realize these two aims conflict with each other. For portraits, you want a focal length in the 50-90mm range and move in to fill the frame.

You want to shoot with as wide an aperture as you can. Unfortunately most lenses are not at their sharpest wide open. Also, the 18-55mm lens doesn't open up all that wide, f/3.5 at 18mm and f/5.6 at 55mm. To get the widest aperture, you can shoot in the P or A modes. If you don't want to leave the point&shoot modes, try using the Portrait mode.

Since you're not paying for film, I suggest you experiment with the different settings and shooting setups, moving closer and farther from the subject, using different focal lengths, and using different apertures, and see what results you get.

Some of the Rokinon (and other ) zoom lenses could only go into MACRO at certain focal lengths- the lens you have "zooms" from 80 to 200 focal length,but is that done by "sliding" a ring forward and back on the lens, or by twisting a different ring that the one that focuses?

It's not the mode, it's the aperture. What you want is called a "narrow depth of field". Depth of field is controlled by three factors: focusing distance, lens focal length, and lens aperture. For portrait work you probably want a focal length in the 50-100mm range and an aperture as large (smaller f/number) as you can get.

How you get the large aperture is up to you. Probably the easiest is to select Aperture-priority mode and crank it as far as it goes.

I encourage you to experiment with it. If you can't get another person to help you, just put an object where you'd prefer to have a head. Use different apertures, and different focal lengths (moving closer or farther to compensate). It's not as if you're paying money for film and processing, after all.

blow the dust out with canned air. if you can focus on the dust, chances are it's on the first lens inside the projector.

All cameras have a minimum focal length. That is the minimum distance they have to be from an object in order to focus clearly. If you have a digital camera with changeable lenses, that minimum focal length is determined by the lens and how it is constructed. If you have a fixed lens digital camera then the manual should tell you what the minimum focal length is.

One other thing to keep in mind is that on most fixed lens digital cameras, there is what is called a macro setting. If you switch to macro mode, it will allow you to get closer to the object and still get a good focus. Your manual should tell you how to turn on that mode.

The macro is good at 4cm at wide angle, 8inches at full telephoto(different distances for any focal length in between). I read that someplace in the manual, I believe.