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Thread: 1/Focal Length & handholdability

  1. #41

    Default Re: 1/Focal Length & handholdability

    Quote Originally Posted by wong1979 View Post
    I have provided links that shows that crop factor needs to be factored in when using the 1/focal length rule. Apparently, some are still not convinced. Anyway, I welcomed any technical theories that may arise to counter the claim. Until then, the best solution is for someone to carry out tests with pictures to prove.

    Thank you all, especially Clockunder for partaking in this discussion. I shall rest my case here
    My advice is not to take everything found on website as the gospel truth. If I want, I can also find links which say no need to take into account the crop factor.

    Just look at compact cameras which are mostly of very high crop factors (6x etc. because of their very very small sensors) and extremely short actual focal lengths. Look at the kind of moderately slow shutter speeds (1/30 etc. even when zoomed to over 100mm on 35mm format equivalent) they're capable of taking without handshake blur with no image stabiliser. The answer is pretty obvious that the crop factor does not come into the picture for handshake blur. Also those prosumer cameras too with mostly 4-6 times crop factors on 2/3", 1/1.8" and 1/2.5" sensor sizes.

    1) is the guideline different for different composition and shooting distance?

    2) Does the actual shift of the actual image on the image sensor depend on the shooting distance?

    Here I'll explain why did I use the same shooting distance as example to illustrate.

    Image the picture below is taken at @50mm on a full frame sensor standing at 5m away and a certain 1/X shutter speed was used to avoid handshake blur. Label it as Pic #F for full frame.




    Now if you use the same 50mm lens on a 1.6x crop factor camera standing at the same position 5m away and then take exactly the same picture at the same 1/X shutter speed. This is what you get (label it as Pic #C for crop factor camera ) because it's exactly the same actual image on the sensor except now the image sensor is smaller and therefore the centre crop :





    Now, the questions :

    1) If there is no handshake blur in pic #F taken at that 1/X shutter speed, do you expect there is handshake blur in Pic #C taken at the same 1/X shutter speed at the same focal length (although the composition is different) at the same distance away (e.g. 5m)?

    The answer for (1) is obviously no. They should be the same since Pic #C is just a crop of Pic #F. In fact, the actual physical image that falls on the sensor in the camera is exactly the same since they are both taken at the same focal length 50mm at the same distance 5m away. The only difference is the crop (composition) and you can simulate exactly a 1.6x crop factor camera by doing a crop on a full frame picture. Yes, big pixel density differences sometimes affects sharpness (as another forumer pointed out, and also depends on whether the pixel density or lens resolution is the limiting factor in those circumstances) but that is a separate issue related to sharpness and resolution.

    If the logical obvious answer is if @50mm full frame, 5m away : 1/X (e.g. 1/50)
    then
    @50mm 1.6x crop factor camera, 5m away : 1/X (e.g. 1/50)


    2) Now if there is no handshake blur taken at 1/X shutter speed @50mm on a 1.6x crop factor camera at 5m away, do you expect handshake blur to appear if you're using the same 1.6x crop factor camera but at further away (e.g. 8m) now and take the same picture at the same 1/X shutter speed?

    In other words, is the guideline different between ? :
    @50mm with 1.6x crop factor camera, 5m away
    vs
    @50mm with 1.6x crop factor camera, 8m away

    For both the guidelines you and I advocate, the guideline does not differ with this difference in distance (i.e. same for 5m and 8m on the same camera).

    In other words, if the guideline is @50mm 1.6x crop factor camera, 5m away : 1/Y
    then
    @50mm 1.6x crop factor, 8m away : 1/Y

    Now we take both (1) and (2) together.

    From (1), our conclusion is that if there is no handshake blur on a full frame taken at 1/X (e.g. 1/50) 5m away, then there is no handshake blur on a 1.6x crop factor camera taken at the same focal length at the same 5m away at the same 1/X shutter speed.

    In other words, if the guideline is @50mm full frame, 5m away : 1/50
    then
    @50mm 1.6x crop factor, 5m away : 1/50

    From (2), we both think that the guideline for the same 1.6x crop factor do not differ with different shooting distances (5m vs 8m).

    But from (1) we know that for @50mm 1.6x crop factor, 5m away, the guideline is 1/X (same as a full frame since focal length and shooting distance is the same and the only difference is Pic #C is a direct crop out of Pic #F).

    Since the guideline for 1.6x crop factor, 5m away is 1/Y = 1/X = 1/50 (from (1)) and it's the same for 8m away for the same camera at the same focal length, we know that Y for 8m is = X = 50

    Therefore, guideline @50mm 1.6x crop factor camera, 8m away : also 1/50

    In other words, if there is no handshake blur at 5m on the 1.6x crop factor camera and the shutter speed to avoid handshake blur is the same for both 5m and 8m away for the same 1.6x crop factor camera, then it can only lead to one logical conclusion for (1) and (2) above to be consistent : the same shutter speed for both full frame and crop factor cameras.


    This only means that the crop factor needs not be accounted for in the guideline.

    If you think the crop factor should be taken into account just because you need to stand further away, inconsistency appear in the shutter speed required for the 1.6x crop factor camera :
    From (1) above :
    @50mm full frame 5m away : 1/50
    @50mm 1.6x crop camera 5m away : 1/50 vs @50mm 1.6x crop camera 8m away : 1/80.

    If you say that @50mm 1.6x crop camera 5m away should be 1/80 instead, then you just saying that a simple crop as in Pic #C in (1) above would affect handshake blur at the same shooting distance 5m at the same focal length 50mm and this is illogical as only the degree in field of view is changed by a crop and nothing else except may be DOF changes. (suggested reading : crop factors in camera and different sensor sizes).

    If you think about the above, the reason for talking about the same shooting distance for illustration becomes clearer now : to establish point (1) above where the physical images on the 2 different image sensor sizes are the same except the crop and then by extension, come to consistent logical answers for the guideline.

    For certain, practically, shooting distance and composition does not matter because shooting distance does not affect how much the actual image on the sensor shifts before the shutter closes. This is most evident in compact Point and Shoot and prosumer cameras.

    Some people have used "higher magnification required" for actual image on sensor to become viewing/print sizes as the argument for a faster shutter speed to avoid handshake blur. But they forget that if there is no handshake blur recorded with a certain shutter speed, there isn't any handshake blur regardless of how many tens or hundred times the actual image is enlarged. Sensor size affects Depth of Field but not how much the actual image shifts on the image sensor before the shutter closes. Same with shooting distance. Only actual focal length affects.

    If you insist on incorporating the crop factor, then there will be inconsistency. Practically, this is vindicated my the billions of clear shots taken by millions of point and shoot cameras without image stabiliser at shutter speeds faster than 1/actual focal length but slower than 1/focal length on 35mm format equivalent. First of all, you need to understand why handshake blur is recorded on the sensor. If you understand, then you would realise that only the actual focal length, amount of handshake and shutter speed affect handshake blur as they determine whether the physical image on the image sensor shifts too much before the shutter closes. The size of the wall (back screen, aka image sensor) has no bearing.

    I've presented my arguments and I rest my case.

    (p.s. just in case you're confused again, the distance between the wall and the torchlight is not the shooting distance but the focal length. When you stand further away from the wall, you increase the focal length and this has nothing to do with shooting distance which is not depicted anywhere in the torchlight analogy).

    Also I don't think I have so steady hands as to shoot 4 stops below the guideline : 1/60 vs guideline based on 35mm format equivalent is 1/280. If shutter speed is at 1/125, all I need to do is aim and shoot because the actual focal length is only 71.2mm fully zoomed even though it's 280mm on 35mm format equivalent. If at 1/60, I have to steady my hands carefully and concentrate when fully zoomed at 71.2mm but sometimes still got handshake blur ).
    Last edited by Clockunder; 7th February 2007 at 03:58 AM.

  2. #42

    Default Re: 1/Focal Length & handholdability

    Point no.1 - I agree totally

    It's from point no.2 onwards that I don't agree with you. Shooting at 8m away with the 1.6 Factored camera still require a speed of 1/X instead of 1/Y(which is an increased shutterspeed) in order to ahieve the sharpness due to "minimum unshakiness" in picture F.

    Here's where you go wrong:

    Supposed with the 1.6 Factored camera, u take at 5m and 8m respectively at 1/X secs. You zoom the face of one of the grils at 100%. The one at 8m away is sharp but it is smaller. Therefore, you will need to magnify 1.6 times to see the difference. And any shakiness would therefore be magnified 1.6 times. But of course, the resolution would be poorer but the shake can still be seen.

    Now, consider this:

    I shoot exactly the same compostion in pic.F with a 50mm lens with a 1.6X Cam at 1/50 secs. At the same distance, I would require a 80mm lens on a 1.0X Cam for the same composition. So I will need 1/80 secs to achieve the same and not 1/50 secs.

    I hope you understand and won't say that I have introduced yet another variable, ie. a different focal length lens, to complicate matters. As I've said, shooting distance is only a natural shooting process that one has unknowingly factor in.

    I reiterate again:

    We take a picture wholly and think that it is a full-frame one even though we are using any crop factored camera. The crop factor is there and it's just that we do not think about it when we shoot.


    p/s: [I wanted to quote your post, but too long, system don't allow ]

  3. #43

    Default Re: 1/Focal Length & handholdability

    aiya so complicated explaination.

    Of course the crop factor is impt in the handholding. Or rather it is the resolution of the sensor that is impt.

    SIMPLE explaination:

    1) 5 meg sensor with a crop factor of 1
    2) 5 meg sensor with a crop factor of 1000

    Try handholding both with a 50mm prime..... COMMON SENSE will tell you it is impossible to handhold 2 which is 50000mm equivalent.

    There are sooo many fallacies in this thread. Just because there is no "visible" shake in sensor 1does NOT mean there is no visible shake in sensor 2. The fact that the sensor is cropped with the same megapixel, means it has MUCH higher resolving power over the small little CROPPED area.

    There are camera shake in EVERY picture. It is just whether it is visible in the picture or not
    Last edited by wind30; 7th February 2007 at 09:58 AM.

  4. #44

    Default Re: 1/Focal Length & handholdability

    Quote Originally Posted by wind30 View Post
    aiya so complicated explaination.

    Of course the crop factor is impt in the handholding. Or rather it is the resolution of the sensor that is impt.

    SIMPLE explaination:

    1) 5 meg sensor with a crop factor of 1
    2) 5 meg sensor with a crop factor of 1000

    Try handholding both with a 50mm prime..... COMMON SENSE will tell you it is impossible to handhold 2 which is 50000mm equivalent.
    It is common sense lor And I take it as you agree with me

  5. #45

    Default Re: 1/Focal Length & handholdability

    ya lar. Actually to be more specific, the handholdability actually depends on pixel density on the sensor, not directly dependent on the crop factor. But ASSUMING both sensors has the same resolution the the sensor will higher crop factor will have a higher pixel density which will be harder to handhold using the same lens.

    Conversely, a 20meg sensor will be twice harder to handhold than a 5 meg sensor of the same crop factor if you view both at 100% crop

  6. #46

    Default Re: 1/Focal Length & handholdability

    Quote Originally Posted by wind30 View Post
    ya lar. Actually to be more specific, the handholdability actually depends on pixel density on the sensor, not directly dependent on the crop factor. But ASSUMING both sensors has the same resolution the the sensor will higher crop factor will have a higher pixel density which will be harder to handhold using the same lens.

    Conversely, a 20meg sensor will be twice harder to handhold than a 5 meg sensor of the same crop factor if you view both at 100% crop
    I disagree with your pixel density theory. But I shall not go into it

  7. #47

    Default Re: 1/Focal Length & handholdability

    why not?

    Lets say you have 3 sensors

    1) 5meg sensor crop 1
    2) 5 meg sensor crop 2
    3) 20 meg sensor crop 1

    Sensor 2 is actually just a cropped version of sensor 3 and has the same handholdability.

    Note that although 2 and 3 has different crop factors they have the SAME handholdability due to the resolution difference. This is assuming you are view all your picture at 100% to check for camera shake.

    Also if you compare two pictures of 1 and 3 at 100%, even if there is no visible camera shake for 1, you can may see some shake in 3 due to the higher resolution. So just remember the higher resolution your camera is, the MORE steady you must hold it if you intend to use its HIGHER resolving power.

  8. #48

    Default 1/Focal Length & handholdability (How abt for VR/IS vs. non VR/IS lens)??

    Quote Originally Posted by wong1979 View Post
    We have read or learnt somewhere that, as a general guide, we should apply the "1/focal length" rule (which is applicable for 35mm format) for the minimum shutter speed in handheld shots.

    (1) Do you think that crop factor has to be factored in when using crop factored sensors?

    (2) If you are to focus a very small object such as a coin using a macro lens at 1:1, does the "1/focal length" rule still hold true?

    Pls share your insight
    Hi...guys..

    Does any one have any experience of the min. shutter speed that can be used for VR/IS lens compare to non-VR/IS lens?? Can we use speed slightly slower than 1/Focal Length for VR lens to get sharp pics?? Thanks...

  9. #49

    Default Re: 1/Focal Length & handholdability (How abt for VR/IS vs. non VR/IS lens)??

    Quote Originally Posted by waterlucky View Post
    Hi...guys..

    Does any one have any experience of the min. shutter speed that can be used for VR/IS lens compare to non-VR/IS lens?? Can we use speed slightly slower than 1/Focal Length for VR lens to get sharp pics?? Thanks...
    IIRC Nikon claims it's 4 stops, but IMO, it's ard 2-3 stops to get the same kind of pics.

  10. #50
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    Default Re: 1/Focal Length & handholdability (How abt for VR/IS vs. non VR/IS lens)??

    Quote Originally Posted by ipin View Post
    IIRC Nikon claims it's 4 stops, but IMO, it's ard 2-3 stops to get the same kind of pics.
    Remember, Nikon VR2 is better than Nikon VR (Nikon's claim)...

    Regards,
    Arto.

  11. #51

    Default Re: 1/Focal Length & handholdability (How abt for VR/IS vs. non VR/IS lens)??

    Quote Originally Posted by Artosoft View Post
    Remember, Nikon VR2 is better than Nikon VR (Nikon's claim)...

    Regards,
    Arto.
    Yes, I was referring to the VR2 of the 18-200mm.

  12. #52

    Default Re: 1/Focal Length & handholdability

    Quote Originally Posted by wong1979 View Post
    Point no.1 - I agree totally

    It's from point no.2 onwards that I don't agree with you. Shooting at 8m away with the 1.6 Factored camera still require a speed of 1/X instead of 1/Y(which is an increased shutterspeed) in order to ahieve the sharpness due to "minimum unshakiness" in picture F.

    Here's where you go wrong:

    Supposed with the 1.6 Factored camera, u take at 5m and 8m respectively at 1/X secs. You zoom the face of one of the grils at 100%. The one at 8m away is sharp but it is smaller. Therefore, you will need to magnify 1.6 times to see the difference. And any shakiness would therefore be magnified 1.6 times. But of course, the resolution would be poorer but the shake can still be seen.

    Now, consider this:

    I shoot exactly the same compostion in pic.F with a 50mm lens with a 1.6X Cam at 1/50 secs. At the same distance, I would require a 80mm lens on a 1.0X Cam for the same composition. So I will need 1/80 secs to achieve the same and not 1/50 secs.

    I hope you understand and won't say that I have introduced yet another variable, ie. a different focal length lens, to complicate matters. As I've said, shooting distance is only a natural shooting process that one has unknowingly factor in.

    I reiterate again:

    We take a picture wholly and think that it is a full-frame one even though we are using any crop factored camera. The crop factor is there and it's just that we do not think about it when we shoot.


    p/s: [I wanted to quote your post, but too long, system don't allow ]
    I understand what you’re trying to say.

    What I see is that the only logical explanation to your proposed guideline is the difference in magnification required for different original image sizes of the same composition to become the same viewing/print sizes. Otherwise, shooting distance and composition are both not relevant as far as the guideline is concerned which says only about focal length (be it actual or 35mm format equivalent). It's quite clear that the guideline remains the same (be it actual or 35mm format equivalent) regardless of shooting distance and composition.

    Just as I’ve said earlier, some people may use this “magnification” argument to support using the 35mm format equivalent focal length in the guideline.

    Now consider :

    For a full frame camera :
    Picture taken 1/50@50mm at 5m away
    Sensor size : 36 x 24mm
    Magnification needed –
    To 8R size (12” x 8”) = 12 x 25.4 / 36 = 8.47x
    ==è 48.47^2 = 71.7x in area


    For 1.6x crop factor camera :
    Picture taken 1/50@50mm at 5m away (i.e. this is actually just a crop image of the one in full frame).
    Sensor size (approximate) : 22.5 x 15mm
    Magnification needed --
    to 4R size (6” x 4”) = 6 x 25.4 / 22.5 = 6.77x in length/breadth/diagonals.
    ==è 6.77^2 = 45.8x in area


    The above means that if you take the 8R picture from the full frame and then crop it (e.g. tear the sides of the picture) to the same composition as the 1.6x crop factor camera, the picture would be :
    12”/1.6 = 7.5”
    8”/1.6 = 5”

    Now, let’s assume that there is no handshake blur in the 8R picture since it’s taken at 1/50 @50mm on the full frame according to the guideline for full frame. Naturally, there is also no handshake blur seen in the 7.5” x 5” cropped picture since it is just a crop from 8R.

    Comparing this 7.5” x 5” picture to the 4R (6” x 4”) picture from the 1.6x crop factor camera, it has :
    1) the same composition
    2) taken at the same distance away 5m
    3) taken at the same focal length 50mm
    4) bigger in size than the 4R (i.e. 7.5” x 5” vs 6” x 4”)
    7.5/6 = 1.25x bigger in length/bread/diagonal and 1.25^2 = 1.57x in area.

    It is actually exacly the same as using the original image on the sensor of the 22.5x 15mm 1.6x crop factor camera taken at the same 50mm at the same distance 5m and then magnified 71.7x in area.

    This can easily be verified :
    7.5” = 7.5 x 25.4 = 190.5mm = 190.5/22.5 = 8.47x in length/breath/diagonal
    = 8.47^2 = 71.7x the image on the sensor of the 1.6x crop factor camera.

    This cropped picture is therefore a higher magnification of the original image on the sensor of the 1.6x crop factor camera than a direct 4R print from the camera.

    What does the above tell us?

    If there is no handshake blur in a bigger 71.7x magnification 7.5” x 5” than the 45.8x magnification in the 4R from the 1.6x crop factor camera, the argument about handshake blur due to bigger magnification needed on the 1.6x crop sensor therefore won’t stand.

    If 1/50 is ok to avoid handshake blur on the full frame, then 1/50 should also be ok for the 1.6x crop factor camera.

    You may of course argue that it’s only 4R small print. What about much bigger prints?

    For much bigger prints, the same logic appears. You would notice that don’t see handshake blur on big billboards which goes into metres in length/breadth and the only thing you see is less sharpness which is the Depth of Field despite it being a more than ten thousands or more times magnification of the original image on the sensor. Even though billboards may be taken at much bigger format cameras, the magnification is still extremely huge and many more hundred times than the mere magnification from 35mm full frame to 8R.

    Magnification affects things like DOF and will only magnify handshake blur if there is handshake blur recorded in the camera’s sensor. If there is no handshake blur recorded by the sensor, then there is no handshake blur to be magnified .

    Some argue that there is always handshake blur recorded and the difference is only the extent, and so they believe that any handshake blur recorded will become visible when magnified enough times. All I can say is that one needs to understand the physics of the image projection and recording on image sensor to appreciate that while handshake is always present, it is practically possible that no handshake blur is recorded on the image sensor. "Practically" here means that as far as what the human eyes can observe including big and extreme big size magnification.


    If you read through my earlier post more carefully, you would understand why the guideline remains at 1/50 for 50mm on different sensor sizes, different composition and shooting distance. Otherwise, lots of contradictions and inconsistencies will show up. Once you have understood, you would also understand why the best comparison is still same focal length at same shooting distance at same shutter speed because it is the same physical image on the image sensor except the crop. Handshake blur is recorded only if the actual physical image shifts more than a certain physical extent before the shutter closes. This physical shift in the image on the sensor is only dependent on the amount of handshake, focal length and shutter speed. The composition (i.e. shooting distances etc.) has no bearing on how much the image shift.

    At the end of the day, it’s up to you to understand the logic and also verify it yourself. I found out from reading and then verify with me using my prosumer camera which has a crop factor of 4 and my cousin’s smaller point and shoot camera and also him using the cameras.

    You may argue that it’s our holding techniques. In the practical world, you will find that most people are able to shoot handheld without handshake blur on the Point and Shoot or Prosumer cameras (such cameras have crop factors of 4-6 times easily) at shutter speed slower than 1/35mm format equivalent focal length but start having handshake problems when the speed falls slower than 1/actual focal length. Take an example of the Canon A70 which has 5.4mm-16.2mm actual focal length (35mm-105mm on 35mm format equivalent). Most people do not have handshake problem shooting at 1/15 at the short end and 1/60 at the long end. If faster than 1/35 is really required to avoid handshake blur for this type of camera sensor size at the short end, then it would render it almost useless in most indoor situations without a tripod. Luckily, this is not the case.

    (p.s. I hope that I won't have to write another long one to explain why practically, difference in pixel density doesn't affect handshake blur. Suffice to say that the difference in pixel density has no major impact on handshake blur but only affects overall sharpness/resolution which is a separate issue from handshake blur).
    Last edited by Clockunder; 7th February 2007 at 11:32 PM.

  13. #53

    Default Re: 1/Focal Length & handholdability

    Maybe you can try to ask Bob Atkins. With his knowledge, he can better argue with your presentation

    A question asked by someone in his forum:

    Handholdability and the 1.6x mag factor on 350D

    Cheers..

  14. #54
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    Default Re: 1/Focal Length & handholdability

    Aiyo....why getting more and more complicated to read.

    So simple thing also make until so confusing...

    Same focal length (50mm), same distance from subject = same 1/focal length (1/50, crop or no crop doesn't matter).

    If everything remain constant except the sensor crop factor, there's no need to factor in the crop factor to increase handholdability.

    The 'cropping' is done after the image is taken, not 'zoom' in then kena crop. So at 1/50, both pictures are just as sharp, but the one on the 1.6x camera will be presented to you as though taken with a 80mm focal length, which in actual fact is first taken at 50mm but crop off the center part of the image for you...

    I understand where everyone is coming from, but try it yourself to believe...

  15. #55
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    Default Re: 1/Focal Length & handholdability

    Quote Originally Posted by Razor54 View Post
    Aiyo....why getting more and more complicated to read.

    So simple thing also make until so confusing...

    Same focal length (50mm), same distance from subject = same 1/focal length (1/50, crop or no crop doesn't matter).

    If everything remain constant except the sensor crop factor, there's no need to factor in the crop factor to increase handholdability.

    The 'cropping' is done after the image is taken, not 'zoom' in then kena crop. So at 1/50, both pictures are just as sharp, but the one on the 1.6x camera will be presented to you as though taken with a 80mm focal length, which in actual fact is first taken at 50mm but crop off the center part of the image for you...

    I understand where everyone is coming from, but try it yourself to believe...
    i believe that apply if the pixel density of the FF and cropped sensor is the same.

  16. #56

    Default Re: 1/Focal Length & handholdability

    I forgot to add this to my post above :

    The same composition as a 1.6x crop factor camera mentioned above can also be achieved by the full frame by standing nearer with the same 50mm lens:

    For a full frame camera :
    Picture taken 1/50@50mm at 3.125m away
    Sensor size : 36 x 24mm
    Magnification needed –
    To 8R size (12” x 8”) = 12 x 25.4 / 36 = 8.47x
    ==è 48.47^2 = 71.7x in area

    Since 1/50 @50mm is used according to the full frame guideline, let's assume there is no handshake blur. Compared to the 4R picture taken at 1/50@50mm 5m away by the 1.6x crop factor camera, this 8R picture is twice the phyiscal size (12" x 8" vs 6" x 4"). In terms of magnification from their original images in their respective sensors, it is 71.7x for this full frame picture compared to 45.8x for the 1.6x crop factor camera.

    Even a bigger magnification of 71.7x won't see handshake blur already, there is no reason to think that a 45.8x magnification would see handshake blur if the same 1/50 is used on the 1.6x crop factor camera.

    Now I shall explain why I said earlier that comparing the same composition in the original full images is not as good as the earlier one where a crop of the full frame picture was compared to the 1.6x crop factor camera picture. In this latest example without any crop, the actual sizes of the original image on their respective sensors are not the same. Only when both pictures are taken at the same distance, then their original images are exactly the same physical size except the crop. It is an apple to apple comparison if the full frame picture taken at the same distance away is cropped and then compared to the one taken by the 1.6x crop factor camera. It was already shown earlier that a bigger 71.7x magnification from full frame to 8R and then cropped to 7.5" x 5" won't see handshake blur and so you can't argue that a smaller magnification 45.8x to 4R in a 1.6x crop factor camera would see handshake blur even when the picture was taken at the same focal length a the same shutter speed from the same distance.

    However, the latest comparison does show clearly that a higher magnification wouldn't show up hanshake blur if there is none. Although the magnification factor is the same 71.7x as the earlier example, the physical size of this uncropped full frame picture is 12" x 8" compared to the cropped 7.5" x 5" earlier and compared to 6" x 4" 4R picture from the 1.6x crop factor camera. All 3 have the same composition.

    Together, these 2 examples show that even a higher magnification do not show up handshake blur in a full frame image and therefore there is no reason to expect magnification to show handshake blur in a 1.6x crop factor when taken at the same focal length at the same handheld guideline shutter speed as the full frame picture.
    Last edited by Clockunder; 8th February 2007 at 08:43 AM.

  17. #57
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    Default Re: 1/Focal Length & handholdability

    Woah... become long and long reading.

    Let it be guys! For those who have extra processing brain to calculate minimum handholdability = focal length x crop factor. Good for them. If they need another factors, think about camera and lens weight? How old are you? Are you have steady hand? When is the last time you drink coffee? What is your heartbeat?

    At the end of the days, photo speak for its quality!

    Move on guys!

    Regards,
    Arto.

  18. #58
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    Default Re: 1/Focal Length & handholdability

    Here is what Pentax has to say on the matter:
    http://www.digital.pentax.co.jp/en/s...ch/vol_13.html

    "...In the case of PENTAX digital SLR cameras, the slowest shutter speed needed to prevent blurred images can be calculated as the reciprocal of the product of the lens focal length multiplied by 1.5. If the focal length of your lens is 70mm, for instance, the product of 70 multiplied by 1.5 equals 105; the reciprocal of this is 1/105, so shutter speeds faster than 1/105 second will minimize the risk of blurred images. This supports the accepted theory that the longer lens is more prone to camera shake.

    The reason why we multiply the focal length by 1.5 is that, even when using lenses with identical focal length and angle of view, PENTAX digital SLRs have a smaller image area than that of 35mm film counterparts. As a consequence, the angle of view narrows, while the focal length is unchanged.
    In other words, when you mount a 50mm lens (in the 35mm format) on a K100D camera body whose multiplication factor is approximately 1.5, you can regard it as a lens with the angle of view equivalent to a 75mm lens (50 x 1.5 = 75)."

  19. #59

    Default Re: 1/Focal Length & handholdability

    Quote Originally Posted by Clockunder View Post
    Magnification affects things like DOF and will only magnify handshake blur if there is handshake blur recorded in the camera’s sensor. If there is no handshake blur recorded by the sensor, then there is no handshake blur to be magnified .

    Some argue that there is always handshake blur recorded and the difference is only the extent, and so they believe that any handshake blur recorded will become visible when magnified enough times. All I can say is that one needs to understand the physics of the image projection and recording on image sensor to appreciate that while handshake is always present, it is practically possible that no handshake blur is recorded on the image sensor. "Practically" here means that as far as what the human eyes can observe including big and extreme big size magnification.
    You write tooo long and confuses the issue. My point is whether the handshake blur can be recorded by the sensor is DEPENDENT on the pixel DENSITY of the sensor which in turn is dependent on the crop factor of the sensor.

    EXAMPLE: 5meg sensor with a crop factor of 1000 will have a VERY VERY HIGH pixel density and WILL RECORD minute amounts of handshake. Thus making handhold virtually impossible. Can't you understand that?

    I am not ASKING you to magnify a sharp jpeg by blowing it up on photoshop. of course you will not see any handshake. What I am saying is get a DIFFERENT sensor with a higher pixel density (either with a higher crop factor or higher megapixel) and TAKE another jpeg and blow up this higher resolution jpeg.

    For the low res Jpeg when blown up, you will see sharp but COARSE details. For the high res Jpeg, you will see more fine details but EVIDENCE of handshake blur which you are unable to see earlier.

    Anyway Pentax also agrees lah. I am sure nikon and canon do too Olympus for one agrees with me as once you go to flash mode, my oly DSLR automatically set the shutter speed to 1/(focal length * crop factor). Ie if you using a 40mm zuiko lens, they set it to 1/80 shutter speed NOT 1/40.


    Aiya just ask yourself, can you handhold a 50mm lens on a 5 meg sensor with a crop factor of 1000????? If you can answer this question, then why argue?

    I really hope you can clear up your confusion and stop spreading misinformation (not the first time you insisted that crop factor is not relevant to handholding) as it is getting very misleading for newbies and such.
    Last edited by wind30; 8th February 2007 at 09:58 AM.

  20. #60

    Default Re: 1/Focal Length & handholdability

    I would not want to point out the errors and mistakes of others directly but just to present my logical answers. Otherwise, I would have a lot to explain how and where their errors and mistakes are.

    The following will hopefully make it very clear and make my arugments complete. I will leave it to readers to decide for themselves what guideline they think is logical.

    Now we take the same full frame image on the sensor again but this time we magnify it by the same factor (i.e. 6.77x in length or 45.8x in area) as the magnification needed for the original 1.6x crop factor image to become 4R (6” x 4”) size.

    Full frame camera :
    Picture taken 1/50@50mm at 5m away
    Sensor size : 36 x 24mm
    Magnification = 6.77x in length
    Size = (36 x 6.77) by (24 x 6.77)
    = 243.7mm by 162.5mm
    = (243.7/25.4)” by (162.5/25.4)”
    = 9.6” x 6.4”

    This size is between 8R and 4R. It can be called 6.4R.

    Now if we crop this 6.4R picture by 1.6x by tearing off the sides around the physical picture, we get
    Size = (9.6”/1.6) by 6.4”/1.6)
    = 6” x 4”
    = 4R size

    This torn picture now becomes exactly the same as the 4R (6” x 4”) picture from the 1.6x crop factor camera in all aspects :

    a)composition + angle of view (since someone mentioned this)
    b)viewing size 4R
    c)original image size on the sensor
    d)magnification 6.77x in length or 45.8x in area,
    e)focal length 50mm
    f)5m away
    g)shutter speed 1/50.

    This means they are in fact exactly the same image.

    This 6.4R picture taken by the full frame has no handshake blur at 1/50 and so its cropped picture to 4R size (which is exactly the same image in all aspects with the picture taken by the 1.6x crop factor camera) also won’t have any handshake blur at 1/50.

    This means that exactly the same minimum shutter speed guideline on the full frame also applies to the 1.6x crop factor camera.
    Last edited by Clockunder; 9th February 2007 at 12:24 AM.

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