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Does your camera have a focus problem?

This Web site has several parts

Part 1: Is there something wrong with my camera?
Part 2: My camera is OK. Is there something wrong with my technique?
Part 3: My camera needs adjusting. Can I do it myself?
Part 4: Frequently asked questions and What if?
Part 5: Advanced focus and lens analysis
Download Focus Test Target

Part 1: Is there something wrong with my camera?

This can be asked about any digital camera whether it is a point and shoot pocket camera or a $5000 DSLR. A great many people have purchased a DLSR from Nikon or Canon and they are not getting the results that they expected. These cameras are mass produced in exotic places and a few have been reported to have focus problems right out of the box. Did you buy a lemon? Do you have buyers’ remorse?. This site is designed to help you love or hate your camera so you can get on with your life. You should only take as many steps as you need to accomplish this goal.

Important things to know

Note: If you are an advanced user and are interested in how all your lenses work with your camera, you should go to Part 5 now.  Part 5 has a more advanced target that will analyze curvature and astigmatism and reveal the peculiarities of different lenses.

The Best Little Focus Target in Idaho.
An inside joke for Texans.

This target can be used without a computer in a camera store or at a garage sale. Not needing a computer speeds up the process of testing and finding the sweet spot for adjusting the camera. This may be used with any camera but is especially suited for Nikon D70 cameras (because that is what I own). You can use the same procedure with other cameras but you will just have to work out “The Move” for your particular model.

This target is the standard photo size, 4x6 inches. In order to maintain its high precision it should be printed by a photo finisher on glossy paper having a printer resolution of 320 dpi native resolution. You can use 300 to 480 with no problems. some of the pixels in the geometric patterns are 2 and 3 pixels wide. Any photo finisher using a Noritsu 3xxx or Frontier printer should be adequate. In the USA this could be Costco, Wal-Mart, Target or a major camera store chain.

Impatient people can use their 600 dpi laser printer or photo ink jet just to see how it works, but I really recommend a digital photograph from a high quality laser photo printer.

Preparing to photograph the target.

Easiest method.  Set your ISO as high as it will go. Noise has nothing to do with focus and you want to use a fast shutter speed if you are going to hand hold the camera. Open the aperture as much as possible. Setting at F4 would be adequate even for a lens that opens wider. We are just going to find the sweet spot and see how close it comes to being OK. Set aperture priority and make sure you are us
ing the central focus sensor only. Set the focus lock to "L". (seen on the right, not set to "L") The target is designed to be used at 50 to 100 mm focal length and at about 1 to 2 feet. If your lens will not focus that close you may want to download the big 8x10 target and focus at a greater distance. Use indirect or diffused daylight from a window if you can. If sunlight is not available consider using the pop up flash if you are going to be hand holding. If you hand hold, make sure you use a speed of at least twice the focal length. 1/250th should be fast enough unless you are using a very long lens.
Your target is going to lay flat on a table and you are going to position the camera at a 45 degree angle +/- 15 degrees. Don’t get crazy about this. It is approximate and this is an easy test.
You can use a tripod if you prefer, but you should use a flash and the highest sync speed for your camera.
camera on tripod
Try to shoot with the center vertical line aligned with the camera vertical line and the horizontal camera line perfectly lined up the horizontal target line. The ends of the dark line on the target  should coincide with the circle in the viewfinder. You should be clipping the left and right edges of the target in the viewfinder.
shooting the target
Take a shot or two to observe proper exposure. The whites should be white and the text should not be blown out. If there are light reflections or shadows on the target, move things around until you get a clear, well exposed shot over the whole image area.

Perform “The Move” as described for the D70, but if you don’t have a D70 figure out how to view an enlarged image on your monitor.

Learning the Move
In order to learn how to conduct rapid checks you should learn this little sequence until it becomes automatic.
1 Press the image display button. (Right Arrow Point on upper left of viewing screen.)
2 Immediately press the QUAL button and 

3 press and hold the ISO button and
4  roll the rear thumb wheel rapidly three times to the right.
3. Release the ISO button. The largest view of the image now appears on the screen and the view is centered on the central focus area.

This is called “The Move”

Evaluating what you see
You should be able to read “Focus Here” if your picture was the Best Little…..
You should be able to see some geometric groups of white lines to the left and right of “Focus Here”.

The first pattern is horizontal lines and should be easily resolvable on any lens. It consists of alternating bars of white and black which are 3/320” thick. Each progressing pattern is either rotated 90 degrees or one pixel smaller on the black and/or white bar. The finest pattern is two black and two white, which is about the limit that you can see on the viewfinder.
Tip the 4 direction star pad to the left and view a similar pattern progressing vertically. Each pattern group is numbered from zero on the reference line and progressing up and down. The coarsest pattern is next to zero in both directions. You should be able to see about the same detail in the coarse pattern next to 1 on the bottom with the coarse pattern next to 2 on the top. This approximates the depth of field expected as 1/3 of the image before and 2/3 of the image beyond the focal point. This is a mythical 1/3. Due to the very close focus distance it may be more like ¼ or 1/5. How far you can go on either direction will depend on the f-stop of the lens taking the picture. (f 4 in this case) Also on the target is a field of phony Latin text which you should not try to translate, but observe the graying of the text and background as the text is further from the focus point.

In Peter Inova’s book on the D70 and Digital photography he debunks some myths and explains things that are commonly misunderstood. I cannot quote because of copyright, but as he explains some of the properties of hyper focal settings he suggests that the rule of thumb of 1/3 of the image before and 2/3 after the ideal focal point are not very accurate descriptions of what happens in real life. It may be close to being true at great distances but as the focal point gets closer it becomes more like ¼ and for really close things like our target could be 1/5. I was very glad to find this out because it was making me crazy trying to be true to the myth. What you want to know is that the center of your focus is the sharpest at the correct spot and that focus will more rapidly deteriorate on the close end. This myth has caused many people in past to believe that they have a back focus situation including the author of a very popular camera forum. See a more detailed discussion in the FAQ section. Also read about “What if my sensor does not align with the focus box I see in my viewfinder.”

If you see what I just described, rejoice! The camera and lens are working perfectly.

If you are someone that wants to manually focus the camera, you may want to repeat the test again for ten repetitions with the auto focus switch turned off. If this fails to give you consistent results, it may or may not be the fault of the camera. We will discuss that in Part 2 or you can just forget about manual focus for a while.

If you are not satisfied with the focus at this time go to Part 2.

Download the test charts
Because these are bit mapped images, they contain pure white and pure black spaces and lend themselves to very efficient compression as TIFF files using ZIP. The uncompressed TIFF file should be easily loaded into any of the newer image processors from Nikon, Canon or Adobe. Print them as is. Do NOT sharpen or resize the targets or you will alter  the ability to hold resolution at the high end.

Click to download Targets

Part 1: Is there something wrong with my camera?
Part 2: My camera is OK. Is there something wrong with my technique?
Part 3: My camera needs adjusting. Can I do it myself?
Part 4: Frequently asked questions and What if?
Part 5: Advanced focus and lens analysis

Other references on focus procedures:

Thanks to Tim Jackson, Phil Askey, Peter Inova and Thom Hogan for educating me with their fine publications. Please visit their sites listed above and help support their work.

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