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01-27-2012, 04:19 AM   #1
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General questions from a novice.

In reading through the forum posts I have come across many abbreviations and terminology connected with dslr photography that I don't understand the meaning of. I have listed just three here, I have more in reserve, and would appreciate someone with the 'knowledge' enlightening me as to their meaning.

1. FF. Is it fast or forward focus and how does it manifest itself?

2. CA. What does it mean?

3. Soft. As in -- when I take photographs towards the long end of a zoom, they appear 'soft' or 'woolly'. Are these just another way of saying out of focus?

Is there anywhere within the forums a comprehensive list of 'terminology' and abbreviations that shows novices like myself their true meaning? If not, would it be possible for such a list to be made? Kind regards.

01-27-2012, 04:38 AM - 1 Like   #2
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Many acronyms are self-explanatory -- they're underlined in the text displays, and clicking on them reveals a translation. But I'll address your specifics:

FF (usually) means Full-Frame, the 36x24mm frame size of many film cameras using 135 (35mm cartridge) films. A very few dSLRs from Canon, Nikon, Sony, have close to FF-size sensors. There is much hope that Pentax may release a FF cam. Our current dSLRs mostly have sensors about half FF size, what we used to call 135/HF (half frame), which was also the original 35mm cine frame size.

FF also sometimes means Front-Focus. Some AF (autofocus) lenses aren't calibrated perfectly, don't focus perfectly, so we adjust their focus point in the camera. Often seen paired with BF, Back-Focus. A similar confusing abbreviation is MF, which can mean Manual Focus, or Medium Format (like a 12- or 220 film camera, or the 645D), or a certain expletive.

CA (usually) means Chromatic Aberrations. The most obvious CA is PF (purple fringing). Any CA happens because different colors of light have different wavelengths, and it's not easy to design a lens (especially zooms and ultrawides) that focus all wavelengths at exactly the same point. A lens that's optimized for the middle of the visual spectrum may not focus correctly at the red and violet ends of the spectrum.

CA also means California or Canada. Whatever.

SOFT is somewhat related, especially for zooms. Primes can be straightforwardly designed to be pretty damn sharp over much of their focus range. But every zoom is a compromise, and many are sharp at certain focal lengths and focus points and not-so-sharp elsewhere. Such softness may be desirable for certain portraiture and hated for all other applications. Softness can be minimized just by not enlarging the image very much. A soft shot at VGA resolution and presentation -- who'll notice?

Sorry, I can't point to any specific jargon-translation sites right now. Best bet is just to gargle the jargon, and click those underlines. Good luck!

Last edited by RioRico; 01-27-2012 at 04:44 AM.
01-27-2012, 04:46 AM   #3
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FF can also mean "Front Focus": Where the focus of the picture is forward of where it was intended. This is noticeable in wider apertures/ narrow depth of field. This is usually a calibration issue and some cameras/lens combinations can be adjusted to a certain degree.
The term "Back Focus" is the same thing, where the focus is behind the intended target.

01-27-2012, 06:21 AM - 1 Like   #4
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QuoteOriginally posted by Finknottle Quote
3. Soft. As in -- when I take photographs towards the long end of a zoom, they appear 'soft' or 'woolly'. Are these just another way of saying out of focus?
Soft is the opposite of sharp. A photo can be soft due to missed focus, or it can be soft for reasons other than focus. Some lenses are not very sharp at certain focal lengths or apertures.
- A lens will be less sharp at its widest aperture and at its narrowest apertures.
- Typically a zoom will be softest at either end of its range.

Low depth of field is sometimes the cause of softness.
-Wide apertures have a very narrow band of focus, so your subject may be sharp at the focus point but quickly become soft away from the focal point.
- Distance from the subject also affects DOF. The closer the object is to the lens, the more shallow the DOF.
- DSLR's have much narrower depth of field compared to a camera with a small sensor. This can be used to advantage in shooting with a DSLR, to isolate the subject, but is often confusing to someone accustomed to a compact camera.
- Long lenses have lower DOF than short.
There are depth of field calculators available on the net that allow you to input your lens, focal length and aperture to show these effects.

I would say that low shutter speed is the most common reason that a photo loses sharpness. Low shutter speed is not a specific number, it varies by focal length. A simple rule of thumb was devised for shooting 35mm film; the shutter speed should be the inverse of the focal length. In other words, if you're shooting at 18mm, you need 1/18s minimum, at 300mm you need 1/300s minimum. Because Pentax DSLR's are 1.5X crop, the speeds should be increased. A 300mm lens has the equivalent field of view of a 450mm lens, so the rule of thumb would be 1/450s. However, Pentax DSLR's also have Shake Reduction, so you can get away with lower shutter speeds, depending on one's holding technique. Of course a tripod negates the shutter speed rule of thumb (be sure to turn off SR when using a tripod).

Since you are new to DSLR's, I would suggest a book that's commonly recommended; Bryan Peterson's Understanding Exposure. It is brilliant and the explanations are non-technical. There are also many resources on line that explain how to use control your camera and exposure. If you are having trouble with a particular kind of photo, post an example here, and we can help troubleshoot.

01-27-2012, 08:35 AM   #5
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You can read all about front and back focus here. Usually, it's fixable:
Fixing Front and Back Focus - Introduction -

FF can also stand for 'full frame'.

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01-27-2012, 10:14 AM   #6
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Thanks a lot guys, I know a little bit more now. Adam, I'll print out your FF article and read it a few times. It is a little above me at the moment but I'll persevere.
01-27-2012, 11:28 AM   #7
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I'm moving this to the Beginner's forum, since it seems the more appropriate place.
01-28-2012, 04:31 AM   #8
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QuoteOriginally posted by Marc Sabatella Quote
I'm moving this to the Beginner's forum, since it seems the more appropriate place.
OK! Boss. Much appreciated.


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