1/focal length carifications


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Nov 4, 2006
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#1
Hi guys. Sorry bout the newbie questions. May I ask 2 questions...

1) How does the 1/focal length thing works?
I know to acheive reasonably sharp photos w/o handshake, it's advisable to shoot at 1/focal length esp when shooting at telelengths. However, how does the focal length affects the handshake? Eg : Is it becoz of the length of the lens? Or the changing of the Centre of Gravity (CG) of the lens when the lens extends? If it's so, wouldn't one be able to shoot with a Canon 70-200mm L, which doesn't extends when zoomed, at 1/70s instead of 1/200s. Assuming u are using a FF.

2) If one is using a crop version eg: 350D with 1.6x crop factor, why must the new focal length be considered in the 1/focal length rule? Eg: When using a Canon 70-200mm L on a 350D, must I shoot at 1 / (200x1.6=320) s or can I still shoot at 1/200s and acheive similar effect.

Thanks :)
 

Buggy

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Aug 16, 2004
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#2
imo it's only a guideline. if your hands are stable, you don't have to follow it everytime. as you go into the tele range, the camera is more sensitive to movement... therefore photos are more likely to turn out blur because of handshake. take a torch or laser pointer. point at somewhere near, then point it somewhere really far... notice the handshake. i'm sure it does makes a difference :)
 

Nov 4, 2006
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#3
imo it's only a guideline. if your hands are stable, you don't have to follow it everytime. as you go into the tele range, the camera is more sensitive to movement... therefore photos are more likely to turn out blur because of handshake. take a torch or laser pointer. point at somewhere near, then point it somewhere really far... notice the handshake. i'm sure it does makes a difference :)
I totally understand this point. But what I'm interested is what causes the handshake when using a lense.
 

theRBK

Senior Member
May 16, 2005
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#4
what causes the handshake when using a lense.
er... inherent instability of human arms... nobody can hold a camera perfectly steady...

when the arms holding the camera shifts slightly, the angle at which the camera is aimed at shifts... but this effect is usually not as visible on shorter lenses as compared to longer lenses (focal length that is) as even slight movements when using a long lens is amplified by the tighter angle of view of the lens... lets say a person's arms are likely to cause a 5 degree variance in angle of the camera aim, the handshake would be more significant if the lens of the camera covers a narrow angle (say a telephoto lens that covers 10 degrees) than if it covers a wide angle (say a wide lens that covers 100 degrees) ...

thus the general 1/focal length guide line... :)
 

Nov 4, 2006
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#5
er... inherent instability of human arms... nobody can hold a camera perfectly steady...

when the arms holding the camera shifts slightly, the angle at which the camera is aimed at shifts... but this effect is usually not as visible on shorter lenses as compared to longer lenses (focal length that is) as even slight movements when using a long lens is amplified by the tighter angle of view of the lens... lets say a person's arms are likely to cause a 5 degree variance in angle of the camera aim, the handshake would be more significant if the lens of the camera covers a narrow angle (say a telephoto lens that covers 10 degrees) than if it covers a wide angle (say a wide lens that covers 100 degrees) ...

thus the general 1/focal length guide line... :)
ic....so the handshake is the same...but just at which focal length does it appears more noticeable? Geesh thanks. Finally understood...
 

J-Chan

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Sep 21, 2005
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#6
ic....so the handshake is the same...but just at which focal length does it appears more noticeable? Geesh thanks. Finally understood...
that would depend more on the shutter speed instead of the focal length..

if you're talking about noticing it in the viewfinder, then that would depend on the individual holding it..
 

theRBK

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May 16, 2005
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#7
ic....so the handshake is the same...but just at which focal length does it appears more noticeable? Geesh thanks. Finally understood...
precisely... so with more noticeable handshake, you would need a higher shutter speed so that the shake is minimized on capture... thus the 1/focal length guide line... longer focal length, higher shutter speed needed :)
 

Jul 19, 2007
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#8
i think ur 1st question has already been answered ;)

so abt the 1.6x crop smaller sensor formats, it really makes no diff. cos the focal length ur considering is the focal length on the lens, and the cam has nothing to do with tt except the shutter speed

so no matter if ur using a 200mm lens on a canon eos 1ds mk III or a PnS cam, the advisable shutter speed to use handheld to prevent camshake would be the same
 

Nov 4, 2006
555
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#9
i think ur 1st question has already been answered ;)

so abt the 1.6x crop smaller sensor formats, it really makes no diff. cos the focal length ur considering is the focal length on the lens, and the cam has nothing to do with tt except the shutter speed

so no matter if ur using a 200mm lens on a canon eos 1ds mk III or a PnS cam, the advisable shutter speed to use handheld to prevent camshake would be the same
Hmm...I've heard that one needs to include the new (1.6xfocal length) into the 1/focal length rule. But yes I guess I understand ur point 2.8photography thanks. Just to confirm. Since 1.6x cams are a cropped version of the FF, the amount of handshake you notice at thru ur viewfinder when using a 200mm lens on both a 1.6x crop cam and FF cam is the same although the effective focal length of the 200m lens on the 1.6x crop cam is 320mm. Am I right? Thanks...
 

yehosaphat

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Oct 28, 2005
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#10
IMO dun be so hard up on theories. As mentioned, these are guides to help you decide if the shutter speed selected might or might not result in handshake. More importantly, go out and shoot. Take note of your own threshold for handshake and improve!!
 

blurry80

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Jul 23, 2007
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#11
sorry to hijack the thread.

To be able to freeze the subject will the shutter speed differ if i use long telephoto compare to wide angle lens?
 

Nov 4, 2006
555
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#12
IMO dun be so hard up on theories. As mentioned, these are guides to help you decide if the shutter speed selected might or might not result in handshake. More importantly, go out and shoot. Take note of your own threshold for handshake and improve!!
Understood. I just want to know how the theory works. :)
 

yehosaphat

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Oct 28, 2005
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#13
Understood. I just want to know how the theory works. :)
No probs... one thing to note is that this theory does not apply always. Like if you are shooting at 10mm, doesnt mean that your shutter speed can be 1/10s! There is a min threshold for everyone do find out what is yours!
 

theRBK

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May 16, 2005
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#14
actually, as it is the angle of coverage that is important in determining 1/focal length, technically the "crop factor" should be taken in consideration... but then again it is just a guide line, and as well human to human difference in stability is so great, just aka aka (roughly) follow the guide line would do... pay more attention to what you are shooting instead of calculating... :)
 

synapseman

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May 6, 2003
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#15
With image-stabilisation systems becoming more prevalent these days, the rule is less significant now. 1/30s @ 300mm is now possible. Of course, you will still need to maintain good shooting habits as if your system weren't stabilised.
 

dw2chan

New Member
Jul 2, 2007
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#16
sorry to hijack the thread.

To be able to freeze the subject will the shutter speed differ if i use long telephoto compare to wide angle lens?
no it wouldnt

and as other ppl have already said. this is just a guideline. you'll need to go out and shoot to see what you can handhold... i myself use 1/(focal length x 2) when using a new lens just to be sure.
 

Jul 19, 2007
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#17
Hmm...I've heard that one needs to include the new (1.6xfocal length) into the 1/focal length rule. But yes I guess I understand ur point 2.8photography thanks. Just to confirm. Since 1.6x cams are a cropped version of the FF, the amount of handshake you notice at thru ur viewfinder when using a 200mm lens on both a 1.6x crop cam and FF cam is the same although the effective focal length of the 200m lens on the 1.6x crop cam is 320mm. Am I right? Thanks...
yup:thumbsup:

if im right (i hope so) then you've got the point. the 'longer focal length' for the 1.6x cam is solely due to the sensor
 

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