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Guest imported_Tesseract

Photonerd Question.

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Guest imported_Tesseract

Help me out dawggs,

 

My digi has a manual focus setting. Since its a sony, it doesnt follow the conventional photo terms and rules...when you twist the focus ring, the indication is in meters, from 0,20m to apeiron.

I'm trying to find the focus setting on some older pictures throught the exif tags that are embeded on the flick. The closest terms i get is focal lenght and the value is on mm. However, im pretty sure that the focal lenght has to do with the aperture, and states the ammount of focus throughout all focal zones in the picture.

example:

 

aperture: 2/ High speed = focus at one point/blurry rest

 

aperture 12/lower speed = focus everywhere.

 

Do i stand correct?

 

can someone study that shit and give me a hint on where i can find the fuckin focus value?

 

 

 

EXIF tag

ImageDescription -                

Make - SONY

Model - CYBERSHOT

Orientation - 1 (top left)

XResolution - 72

YResolution - 72

ResolutionUnit - 2 (inch)

DateTime - 2003:10:06 19:32:11

YCbCrPositioning - 2 (datum point)

ExifOffset - 232

ExposureTime - 10/100 seconds

FNumber - 2.4000

ExposureProgram - 1 (manual control)

ISOSpeedRatings - 200

ExifVersion - 220

DateTimeOriginal - 2003:10:06 19:32:11

DateTimeDigitized - 2003:10:06 19:32:11

ComponentsConfiguration - 1 2 3 (YCbCr)

CompressedBitsPerPixel - 2 (average)

ExposureBiasValue - 0.0000

MaxApertureValue - F 2.04

MeteringMode - 3 (spot)

LightSource - 3 (tungsten)

Flash - 0 (no flash)

FocalLength - 48.5000 mm

FlashPixVersion - 100

ColorSpace - 1 (sRGB)

ExifImageWidth - 2560

ExifImageHeight - 1920

InteroperabilityOffset - 650

FileSource - 3 (digital still camera)

SceneType - 1 (directly photographed)

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Guest imported_Tesseract

wake up nerds!

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Guest imported_Tesseract

Focal Length

By Phil Askey

 

Focal length is measured in millimetres, it is defined as the distance from the lens to a point where parallel rays are focused to a point (diverge), traditionally measured in millimetres (mm). The lens on a consumer digital camera is marked with its focal length (or range of focal lengths if it's a zoom lens). This is typically a very small number such as 6 - 15mm, in traditional 35mm photography everyone is "used to" the common focal lengths of 28mm, 50mm, 200mm etc.

 

Because the sensor in a digital camera is much smaller than a 35mm negative the lenses can be made smaller (because of this they have to be of a much higher quality), to get the true focal length you need to multiply this small size by a value called the "focal length multiplier" (this is especially important for digital SLR's which take normal 35mm lenses).

 

For example, the lens on the Canon PowerShot Pro 70 is marked 6 - 15mm, however the "zoom" of the lens is always quoted as 28mm - 72mm, therefore to make the focal lengths more understandable we are actually multiplying the lenses focal length by 42/3.

 

35mm Equivalent

All digital camera manufacturers publish this "35mm equivalent" focal length simply because people are used to hearing it and knowing what kind of image a 28mm lens produces compared to a 50mm lens, some common lens sizes (focal lengths):

 

<20mm = Super Wide angle

24mm - 35mm = Wide angle

50 mm = Normal, the same picture angle as your eye (46o).

80mm - 300mm = Telephoto

>300mm = Super Telephoto

Please note also that focal length has a direct effect on perspective.

 

Ok, i nailed that one...focal lenght seems to be the zoom value on the lens.

 

I cant believe theres no data in the EXIF tag that tells me where it was focused....

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The focus zones have nothing to do with the aperature. It depends on the camera how many focus zones the camera has, a standard camera would have only one whereas a canon 300d has 7 and you can set the focus with any one of them or all of them. As far as I know Exif tags dont register focus zones. But depending on the picture you can perhaps sopt where the image was focused just by looking at it. Aperature is the amount of light the camera lets in, the lower the number the more light. More light gives a softer focus though so it will not be as sharp an image.

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What you're seeing in the EXIF is the true focal length of the lens at time of picture. That is, how far you were zoomed in and out. I'm assuming that sony didn't see it necessary to record that distance of the object the camera was focused on, and thus you probably won't have this information. I don't see anything resembling it in any of the fields there.

 

If you're dealing with a camera with a non-optical viewfinder, manual focus is going to be turbo useless anyway. I'd suggest not using it.

 

Here is a sample EXIF from my camera, as you can see no focal distance information on it, either. Probably not a common thing to include.

 


Make - SIGMA
Model - SIGMA SD9
Orientation - Top left
XResolution - 180
YResolution - 180
ResolutionUnit - Inch
Software - Adobe Photoshop 7.0
DateTime - 2004:10:24 15:42:16
YCbCrPositioning - Co-Sited
ExifOffset - 208
ExposureTime - 1/350 seconds
FNumber - 8.00
ExposureProgram - Normal program
ISOSpeedRatings - 100
ExifVersion - 0220
DateTimeOriginal - 2004:10:22 15:58:56
DateTimeDigitized - 2004:10:24 15:29:40
ComponentsConfiguration - YCbCr
ExposureBiasValue - 0.00
MaxApertureValue - F 5.66
MeteringMode - Multi-segment
Flash - Not fired
FocalLength - 200 mm
FlashPixVersion - 0100
ColorSpace - sRGB
ExifImageWidth - 912
ExifImageHeight - 243
SensingMethod - One-chip color area sensor
FileSource - DSC - Digital still camera
CustomRendered - Custom process
ExposureMode - Auto
WhiteBalance - Manual
FocalLengthIn35mmFilm - 340 mm
SceneCaptureType - Standard

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