Definition & Cal of stops


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Hosea

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#1
Hi , Appreciate if someone could help me to understand more about the definition of stops ( both in shuttle speed & aperture).


It would be good if there is a website detailing on this.
Thanks! :D
 

May 5, 2004
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#4
http://www.fotoinfo.com/info/technicalinfo/shutter.html

note that the list at the end is only meant to be illustrating the relationship between the shutter speed and aperture. High shutter = less light on film, therefore compensate by open lens iris (aperture) larger. the converse is the same.

with regards to stops, it is refering to the "clicks" on the dials. eg if a shot requires exposure of 1/60 @ f11, if you increase the shutter from 1/60 to 250, you would have increased shutter speed by 2 stops (1/60, 1/125, 1/250). Higher shutter speed = less light therefore to acheive correct exposure then is to open the iris (aperture) of the lens to allow sufficient light to come into the camera, and by how much? 2 stops, from f11 to 5.6 (f1, f8, f5.6.)

more help:
http://www.betterphoto.com/forms/qnaDetail.asp?threadID=5109
http://www.photosecrets.com/p11.html
http://allsands.com/Hobbies/photographyaper_tqc_gn.htm

plenty of reading but some pple have difficulty grasping the concept, so if u got it, dun worry abt the articles.
 

Hosea

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#5
Thanks Nash, this gonna help, will read it.
I have a case when someone use the handmeter to meter on the object, found the speed to be 4 ". subsequently were told to increase by 2 stops and was told it is (4x2) x2 =16 "
Is this right?
 

May 5, 2004
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#6
yes, but remember that cameras has got their quirks, eg decrease 1 stop from 1/60 should be 1/120 rite? wrong! it is 1/125! why? beats me! in anycase most electronic devices nowadays can handle "in between" increments of stops, unlike the old days when a click is a click
 

IronKong

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#7
I think should be 15 not 16. One way to know the stops is to set your camera to TV (Shutter prioty) and if you camera in in half stop increment, everytime you turn the dial buttion on your camera it is half stop different so turn 4 time you will be able to get 2 stop different which is 15.
 

Hosea

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#8
IronKong said:
I think should be 15 not 16. One way to know the stops is to set your camera to TV (Shutter prioty) and if you camera in in half stop increment, everytime you turn the dial buttion on your camera it is half stop different so turn 4 time you will be able to get 2 stop different which is 15.
Oh guys, please help to explain why it is (4x2)x2 and not just 4x2 since it is only 2 stops?
Sorry really want to clear this out of my chest. :dunno:

If it is set to half stop, I might just forgot and click 2 times and thought it is 2 stops :cry: would this happen. How to have a quick recall of what to do leh?? :bigeyes:
 

May 5, 2004
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#9
because every stop is doubling(x2) or halving(1/2) the amt of light. so one stop increase= current number of stop x2. 2 stops = x2x2 or x4.
 

Hosea

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#10
NashVillian said:
because every stop is doubling(x2) or halving(1/2) the amt of light. so one stop increase= current number of stop x2. 2 stops = x2x2 or x4.
Thank you Nash.
So for the Aperture, I must remember what is the next stop ( e.g. 8,5.6,4)
inorder to determine what would be 2 stops of F,right?
or just turn the dial as mentioned by Ironkong...but I should also know whether I am setting a half stop or full stop..think F setting is more difficult than shutter speed.
 

justarius

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#11
simple sequence of full stops:
shutter speed: 1, 1/2, 1/4, 1/8, 1/15, 1/30, 1/60, 1/125, 1/250, 1/500....
aperture: f1, f1.4, f2, f2.8, f4, f5.6, f8, f11, f16, f22, f32....

note that it's not simply X2 for aperture due to the fact that it's area we are talking about. The factor is in fact ~1.4 or root 2.
 

May 5, 2004
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#12
if u are using hand held meters, then u can adjust the meter until the aperture is at a nice round number that is easier to set on ur cam, then set the corresponding shutter on ur cam. on camera u will have the light meter as u look thru the viewfinder (slr/dslr), playing around with the settings in accordance to your preference (dof for example), ensuring correct exposure at the same time.
 

Hosea

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#13
justarius said:
simple sequence of full stops:
shutter speed: 1, 1/2, 1/4, 1/8, 1/15, 1/30, 1/60, 1/125, 1/250, 1/500....
aperture: f1, f1.4, f2, f2.8, f4, f5.6, f8, f11, f16, f22, f32....

note that it's not simply X2 for aperture due to the fact that it's area we are talking about. The factor is in fact ~1.4 or root 2.
Thank Just, the mentioned of root 2 helps to clarify my perception , so if I can remember , i will just recall 1.4 :bsmilie:
 

Hosea

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#14
NashVillian said:
if u are using hand held meters, then u can adjust the meter until the aperture is at a nice round number that is easier to set on ur cam, then set the corresponding shutter on ur cam. on camera u will have the light meter as u look thru the viewfinder (slr/dslr), playing around with the settings in accordance to your preference (dof for example), ensuring correct exposure at the same time.
I am yet to buy a hand-held meter, but saw someone using it... and thought once you press the meter, its figure of aperture and shutter will auto come out. can adjust the meter :dunno:
Just wonder the meter of digi-camera is accurate, many pro said it is not so :what:
 

ziploc

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#15
You can still use the "x2" method to memorize the f-stops... just remember the first 2 f-values: f/1 and f/1.4. The rest are "x2" of these 2 values: f/2 & f/2.8; f/4 & f/5.6; f/8 & f/11, etc. :)
 

Hosea

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#16
ziploc said:
You can still use the "x2" method to memorize the f-stops... just remember the first 2 f-values: f/1 and f/1.4. The rest are "x2" of these 2 values: f/2 & f/2.8; f/4 & f/5.6; f/8 & f/11, etc. :)
:thumbsup: easier now.
 

ziploc

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#17
Hosea said:
I am yet to buy a hand-held meter, but saw someone using it... and thought once you press the meter, it figure of aperture and shutter will auto come out. can adjust the meter :dunno:
Just wonder the meter of digi-camera is accurate, many pro said it is not so :what:
Hi Hosea,

On a light meter, you can select either the aperture or shutter speed that you want, then let the meter determine the other value based on the exposure measured.

On accuracy of the on-camera meters, not that they are "inaccurate". For consistency, all meter presumes that the subjects are of average reflectance (or 18% gray). On-camera meters measure the reflected light from the subject and it's measurement will be affected by the reflectance of the subject, e.g. metering a black cat and a white cat will give different readings under the same lighting condition. One way to overcome this problem is to meter off an 18% gray card.

Handheld light meters are incident light meters which read the intensity of the light falling onto the subject directly and hence are not affected by the reflectance of the subject.

Hope that helps. :)
 

Hosea

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#18
ziploc said:
Hi Hosea,

On a light meter, you can select either the aperture or shutter speed that you want, then let the meter determine the other value based on the exposure measured.

On accuracy of the on-camera meters, not that they are "inaccurate". For consistency, all meter presumes that the subjects are of average reflectance (or 18% gray). On-camera meters measure the reflected light from the subject and it's measurement will be affected by the reflectance of the subject, e.g. metering a black cat and a white cat will give different readings under the same lighting condition. One way to overcome this problem is to meter off an 18% gray card.

Handheld light meters are incident light meters which read the intensity of the light falling onto the subject directly and hence are not affected by the reflectance of the subject.

Hope that helps. :)
Thanks Zip, this really helps.
btw, I think there is a selection for us to meter based on reflection and ?,can't recall. Understand if u hand meter, dont use the reflection,not so accurate :dunno: aiyah, cant recall there other option on the hand held meter.
This meter so exp , Ruby selling at $300 ( with lcd light) and S$260 w/o light :(
btw, where to get an 18% gray card? or any gray card will do?
 

ziploc

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#19
Hi Hosea,

Mid to high range handheld meters (e.g. Sekonic L-308 or Polaris SPD-100) can do both flash and incident/reflected metering (changing between incident and reflected by sliding a dome), and some high end ones (e.g. Sekonic L-508) also offer spot metering. The spot meter on handheld meters are also reflected light meters. They are better then those of the on-camera ones in that their metering angles (or "spot") are consistent and are not affected by focal length of the lens.

You can't just use any gray card. The gray needs to be neutral gray (mid gray, i.e. 18% gray). You can get the 18% gray card from the usual camera equipment shops. But it is not essential as there are plenty of neutral gray objects in our surrounding, and you just need to learn to identify them. Btw, neutral gray objects can be in any color and not necessary in "gray".

Hope that helps. :)
 

Hosea

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#20
ziploc said:
Hi Hosea,

Mid to high range handheld meters (e.g. Sekonic L-308 or Polaris SPD-100) can do both flash and incident/reflected metering (changing between incident and reflected by sliding a dome), and some high end ones (e.g. Sekonic L-508) also offer spot metering. The spot meter on handheld meters are also reflected light meters. They are better then those of the on-camera ones in that their metering angles (or "spot") are consistent and are not affected by focal length of the lens.

You can't just use any gray card. The gray needs to be neutral gray (mid gray, i.e. 18% gray). You can get the 18% gray card from the usual camera equipment shops. But it is not essential as there are plenty of neutral gray objects in our surrounding, and you just need to learn to identify them. Btw, neutral gray objects can be in any color and not necessary in "gray".

Hope that helps. :)
Thanks a lot Ziploc, learn much from you!
Cheers!
 

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