kb244
3rd of February 2005 (Thu), 02:53
I had this conversation with a friend earlier, posing the possible question, whether or not the 1.6x crop factor will affect camera shake, due to FOV.
My Original Thoughts :
I can get handheld shots clear without camera shake, shooting at 1/50 , on a 50mm lens, when the camera would be doing 80mm on the FOV. Or better yet, 1/125 on my 28-135. The crop factor is just 1.6x meaning, the sensor is only that much coverage of where the light hits the plane. until it hits the sensor its still the same. Its the same thing as sticking a 50mm onto a film camera with full frame, then cutting out the 1.6x crop. The back of the lens is the same distance from the sensor as it is on a film or full frame camera. So the Crop Factor does NOT affect the shutter speed rule.
If it did, you'd see all the non-1Ds users, trying to figure out what they need to set their shutter speeds on 400mm lens when the crop factor gona make them appear 640mm, and other calculations.
Its important to understand, its a 1.6 Crop , not a 1.6 magnification.
The dialog :
Session Start (kblessinggr:Anonymous): Thu Feb 03 03:40:33 2005
kblessinggr: hows it going
Anonymous pretty good, you?
kblessinggr: pretty good, question, whats your background in cameras, you able to handle a question of optics?
Anonymous well, my background in cameras is as a photographer, but I was a physics major in college so optics shouldn't be a huge deal
kblessinggr: http://www.iphotoforum.com/forum/viewtopic.php?t=12467
kblessinggr: a question of camera shake being affected by the 1.6x crop factor or not
kblessinggr: i've stated why i think it doesnt, but wouldnt mind being proven wrong
kblessinggr: as if i was wrong, i could correct the mistake to make sure i get good pictures.
Anonymous ok, let me read the thread
Anonymous although there was a question on this somewhere else a while ago, so I still have the info somewhat fresh in memory
kblessinggr: i'm not a physics expert, but it just seems logically wouldnt affect, unless there was something different between the distances light travles between the back of the lens to the sensor plane.
{EDITED OUT USELESS CHIT CHAT HERE}
Anonymous ok, here's how it works
Anonymous the crop factor does come into play with camera shake
kblessinggr: course i wonder how much, i'm sure its not as simple as doing 1/320 , for a 200mm lens, by multiplying to 1.6x
Anonymous the amount of camera shake depends on two things, the apparent movement between the subject and the image on the film plane and the limit of sharpness of the image
Anonymous the apparent movement is determined by the actual radial deflection (the amount the camera shakes) and the focal length of the lens
Anonymous an increase in either of the two leads to more apparent movement
Anonymous next is the apparent sharpness or sharpness threshold
kblessinggr: course subject movement isnt camera shake :D
kblessinggr: but i see where yer going
Anonymous the apparent sharpness is defined by the size of the circle of confusion and the size of the negative or sensor
Anonymous smaller sensors require a smaller circle of confusion to have equivalent apparent sharpness
Anonymous that's why a large format camera can produce a sharper image than a 35mm camera even though most large format lenses have less physical resolving power than most good 35mm lenses
Anonymous so as you decrease the size of the sensor, you must decrease the size of the circle of confusion to maintain the same apparent sharpness
Anonymous so the limits of the apparent movement between camera and subject become narrower as the format becomes smaller
Anonymous and although we don't necessarily treat subject movement the same as camera shake from a photographer's perspective, from a physical perspective they're the same thing
kblessinggr: i guess the real question is, if you have a 300mm lens, and the general rule is 1/(focal length), to keep it sharp. And I know its not 1/(1.6xFocal Length), to compensate for this, what would one require shutter speed, to match the camera shake-free of the 35mm plane
Anonymous that is a much easier question to answer
Anonymous the "general rule" is completely random BS
kblessinggr: well given in a perfect world, where light is always good
Anonymous the necessary shutter speed to get a sharp photo depends on the person holding the camera more than the actual shutter speed
Anonymous it's just sort of a guide point
Anonymous I know people that have a hard time with camera shake when using 50mm lenses, where as I can usually do fine with a 200mm lens (plus the 1.6x crop factor) at around 1/90
Anonymous it just depends on how steady you can be
kblessinggr: ok, but lets say , with a 50mm lens, I'm able to shoot at 1/50 as i described, without a problem, would myself shooting a 50mm on a 35mm film camera, produce a sharper image, in the area croped out
Anonymous no
Anonymous the sharpness is the same in the area croppe
Anonymous ^cropped
kblessinggr: i guess what i'm trying to say is the same as what he's saying, if he can shoot an event at 300mm, handheld using 1/320 or so, how much would one have to increase the shutterspeed on the 1.6x crop to gain equivilant stability
Anonymous well, 1/500
kblessinggr: because if the crop factor does affect camera shake, how much does it affect it, is the question so that nessary changes can be made.
Anonymous it would be a direct proportion
Anonymous just multiply your actual focal length by 1.6 to get your apparent focal length
Anonymous then plug that into the general rule
kblessinggr: so it would be 1/(1.6xFocal Length), provided that 1/(focal) is stable enough for you
Anonymous yeah, for the most part
Anonymous but it's really not that useful of a piece of info
kblessinggr: tho it is interesting that its normally never bought up. Because on my Drebel, say my macro lens, 105mm , I can do fine 1/100 or so. but 1/100 for a 168 apparent focal length been pretty good for my steady hands
kblessinggr: specially considering I shoot alot of pictures @ 1/125 on my 28-135 , tho 1/125 @ 216mm
kblessinggr: I must have much steadier hands than most other folks
Anonymous yeah, but the important thing is that the rule is just someone's random suggestion
Anonymous it's really not based on anything whatsoever
kblessinggr: so basically camera shake is affected by focal length, but what you do with that information is pointless, other than take a few trial shots, and adjust your shutter for what works.
kblessinggr: erm affected by crop factor
Anonymous exactly
Anonymous and focal length
Anonymous but yes
Anonymous the rule doesn't apply to much of anything
Anonymous it's just something you tell people so that they shut up and stop asking questions
kblessinggr: but theoretically means the same person could possibly get clearer shots from a 35mm film camera in the sense of camera shake, and their normal usage of it
Anonymous most people taking a photography class would rather learn a concrete "rule" than be told to just go find out for yourself
Anonymous yeah
Anonymous well, not exactly
Anonymous you have to also take into account the increase in focal length
Anonymous say, for example, I wanted to take two identical photos
kblessinggr: i know it seems a bit fuzzy, but what you say does make sense, but whats unclear is "how much" it affects.
Anonymous one with a digital camera with a 1.6x crop factor
Anonymous and the other with a 6x4.5 medium format camera
Anonymous and I want the two to be composed identically so I'm just comparing raw image quality
Anonymous if I use a 50mm lens on the digital
kblessinggr: course yer changing your distance from the subject , and changing the focal length of the lens to compose them the same
kblessinggr: or one or the other
Anonymous nope, subject distance has to stay the same
Anonymous but focal length does change
Anonymous I would have to use about a 150mm lens on the medium format
kblessinggr: so 50mm on digi, 80mm on 35mm
Anonymous so the amount of apparent subject movement increases from the digital to the MF because of the required increase in focal length
Anonymous so ultimately, you end up back where you started
kblessinggr: how steady can you hold it?
kblessinggr: hehe
Anonymous dealing with conversions between formats can be kind of confusing
kblessinggr: hrm, mind if i cut this into the thread.
Anonymous no
kblessinggr: might be easier for folks to follow the conversation :P
kblessinggr: and its already typed up
Your thoughts? Clarifications? Objections?
My Original Thoughts :
I can get handheld shots clear without camera shake, shooting at 1/50 , on a 50mm lens, when the camera would be doing 80mm on the FOV. Or better yet, 1/125 on my 28-135. The crop factor is just 1.6x meaning, the sensor is only that much coverage of where the light hits the plane. until it hits the sensor its still the same. Its the same thing as sticking a 50mm onto a film camera with full frame, then cutting out the 1.6x crop. The back of the lens is the same distance from the sensor as it is on a film or full frame camera. So the Crop Factor does NOT affect the shutter speed rule.
If it did, you'd see all the non-1Ds users, trying to figure out what they need to set their shutter speeds on 400mm lens when the crop factor gona make them appear 640mm, and other calculations.
Its important to understand, its a 1.6 Crop , not a 1.6 magnification.
The dialog :
Session Start (kblessinggr:Anonymous): Thu Feb 03 03:40:33 2005
kblessinggr: hows it going
Anonymous pretty good, you?
kblessinggr: pretty good, question, whats your background in cameras, you able to handle a question of optics?
Anonymous well, my background in cameras is as a photographer, but I was a physics major in college so optics shouldn't be a huge deal
kblessinggr: http://www.iphotoforum.com/forum/viewtopic.php?t=12467
kblessinggr: a question of camera shake being affected by the 1.6x crop factor or not
kblessinggr: i've stated why i think it doesnt, but wouldnt mind being proven wrong
kblessinggr: as if i was wrong, i could correct the mistake to make sure i get good pictures.
Anonymous ok, let me read the thread
Anonymous although there was a question on this somewhere else a while ago, so I still have the info somewhat fresh in memory
kblessinggr: i'm not a physics expert, but it just seems logically wouldnt affect, unless there was something different between the distances light travles between the back of the lens to the sensor plane.
{EDITED OUT USELESS CHIT CHAT HERE}
Anonymous ok, here's how it works
Anonymous the crop factor does come into play with camera shake
kblessinggr: course i wonder how much, i'm sure its not as simple as doing 1/320 , for a 200mm lens, by multiplying to 1.6x
Anonymous the amount of camera shake depends on two things, the apparent movement between the subject and the image on the film plane and the limit of sharpness of the image
Anonymous the apparent movement is determined by the actual radial deflection (the amount the camera shakes) and the focal length of the lens
Anonymous an increase in either of the two leads to more apparent movement
Anonymous next is the apparent sharpness or sharpness threshold
kblessinggr: course subject movement isnt camera shake :D
kblessinggr: but i see where yer going
Anonymous the apparent sharpness is defined by the size of the circle of confusion and the size of the negative or sensor
Anonymous smaller sensors require a smaller circle of confusion to have equivalent apparent sharpness
Anonymous that's why a large format camera can produce a sharper image than a 35mm camera even though most large format lenses have less physical resolving power than most good 35mm lenses
Anonymous so as you decrease the size of the sensor, you must decrease the size of the circle of confusion to maintain the same apparent sharpness
Anonymous so the limits of the apparent movement between camera and subject become narrower as the format becomes smaller
Anonymous and although we don't necessarily treat subject movement the same as camera shake from a photographer's perspective, from a physical perspective they're the same thing
kblessinggr: i guess the real question is, if you have a 300mm lens, and the general rule is 1/(focal length), to keep it sharp. And I know its not 1/(1.6xFocal Length), to compensate for this, what would one require shutter speed, to match the camera shake-free of the 35mm plane
Anonymous that is a much easier question to answer
Anonymous the "general rule" is completely random BS
kblessinggr: well given in a perfect world, where light is always good
Anonymous the necessary shutter speed to get a sharp photo depends on the person holding the camera more than the actual shutter speed
Anonymous it's just sort of a guide point
Anonymous I know people that have a hard time with camera shake when using 50mm lenses, where as I can usually do fine with a 200mm lens (plus the 1.6x crop factor) at around 1/90
Anonymous it just depends on how steady you can be
kblessinggr: ok, but lets say , with a 50mm lens, I'm able to shoot at 1/50 as i described, without a problem, would myself shooting a 50mm on a 35mm film camera, produce a sharper image, in the area croped out
Anonymous no
Anonymous the sharpness is the same in the area croppe
Anonymous ^cropped
kblessinggr: i guess what i'm trying to say is the same as what he's saying, if he can shoot an event at 300mm, handheld using 1/320 or so, how much would one have to increase the shutterspeed on the 1.6x crop to gain equivilant stability
Anonymous well, 1/500
kblessinggr: because if the crop factor does affect camera shake, how much does it affect it, is the question so that nessary changes can be made.
Anonymous it would be a direct proportion
Anonymous just multiply your actual focal length by 1.6 to get your apparent focal length
Anonymous then plug that into the general rule
kblessinggr: so it would be 1/(1.6xFocal Length), provided that 1/(focal) is stable enough for you
Anonymous yeah, for the most part
Anonymous but it's really not that useful of a piece of info
kblessinggr: tho it is interesting that its normally never bought up. Because on my Drebel, say my macro lens, 105mm , I can do fine 1/100 or so. but 1/100 for a 168 apparent focal length been pretty good for my steady hands
kblessinggr: specially considering I shoot alot of pictures @ 1/125 on my 28-135 , tho 1/125 @ 216mm
kblessinggr: I must have much steadier hands than most other folks
Anonymous yeah, but the important thing is that the rule is just someone's random suggestion
Anonymous it's really not based on anything whatsoever
kblessinggr: so basically camera shake is affected by focal length, but what you do with that information is pointless, other than take a few trial shots, and adjust your shutter for what works.
kblessinggr: erm affected by crop factor
Anonymous exactly
Anonymous and focal length
Anonymous but yes
Anonymous the rule doesn't apply to much of anything
Anonymous it's just something you tell people so that they shut up and stop asking questions
kblessinggr: but theoretically means the same person could possibly get clearer shots from a 35mm film camera in the sense of camera shake, and their normal usage of it
Anonymous most people taking a photography class would rather learn a concrete "rule" than be told to just go find out for yourself
Anonymous yeah
Anonymous well, not exactly
Anonymous you have to also take into account the increase in focal length
Anonymous say, for example, I wanted to take two identical photos
kblessinggr: i know it seems a bit fuzzy, but what you say does make sense, but whats unclear is "how much" it affects.
Anonymous one with a digital camera with a 1.6x crop factor
Anonymous and the other with a 6x4.5 medium format camera
Anonymous and I want the two to be composed identically so I'm just comparing raw image quality
Anonymous if I use a 50mm lens on the digital
kblessinggr: course yer changing your distance from the subject , and changing the focal length of the lens to compose them the same
kblessinggr: or one or the other
Anonymous nope, subject distance has to stay the same
Anonymous but focal length does change
Anonymous I would have to use about a 150mm lens on the medium format
kblessinggr: so 50mm on digi, 80mm on 35mm
Anonymous so the amount of apparent subject movement increases from the digital to the MF because of the required increase in focal length
Anonymous so ultimately, you end up back where you started
kblessinggr: how steady can you hold it?
kblessinggr: hehe
Anonymous dealing with conversions between formats can be kind of confusing
kblessinggr: hrm, mind if i cut this into the thread.
Anonymous no
kblessinggr: might be easier for folks to follow the conversation :P
kblessinggr: and its already typed up
Your thoughts? Clarifications? Objections?