Daedalus2000 Posted October 30, 2015 Author Share #41 Â Posted October 30, 2015 Advertisement (gone after registration) Yes, indeed, and the article in the Wikipedia then goes on: Â In the case under discussion here, however, someone asked how his existing MF lens would perform on a FF camera, in which case Michael's use of the cropping factor was consistent with normal use. Actually, the whole discussion about the use of the "crop factor" was quite superfluous as it ought to be a known fact that the sensor in S type cameras is larger than the sensor in the SL. No confusion about the direction of the cropping formula is really possible, this being a serious forum. Â I know that Michael is a guy that knows his stuff, I justed wanted to highlight that with a different reference the answer is confusing to people (almost all) who use the 35mm FF sensor as the reference. And of course I do not believe everything on the internet, but I used wikipedia as some sort of reference because many years of scientific training had told me to try to be precise and use references to help a discussion. Â Just to show you how confusing it can be if the reference changes, let's discuss what is the crop factor of a T lens on the SL.. What is the reference sensor for this question? Link to post Share on other sites More sharing options...
Advertisement Posted October 30, 2015 Posted October 30, 2015 Hi Daedalus2000, Take a look here What's this "crop factor" (OT from Leica SL sensor). I'm sure you'll find what you were looking for!
lct Posted October 30, 2015 Share #42  Posted October 30, 2015 Yes, but only when you want to compare the FOV of the lens when used on a FF camera with the FOV that lens yields with another image size. [...] Not when we calculate CoC, pop. Link to post Share on other sites More sharing options...
CheshireCat Posted October 30, 2015 Share #43  Posted October 30, 2015 CheshireCat: You know perfectly well that you are not to insult other members. Calling Michael's well formulated reply in answer to a well formulated question "BS" may be acceptable where you  live; it is not here.  Sorry about the "BS" term, we love it here Let's say it stands for "Beautiful Sentences" In any case, neither the original question nor the answer were well formulated because they used the "unspecified" variable Link to post Share on other sites More sharing options...
pop Posted October 30, 2015 Share #44  Posted October 30, 2015 Just to show you how confusing it can be if the reference changes, let's discuss what is the crop factor of a T lens on the SL.. What is the reference sensor for this question? I don't see where any confusion should come from.  Clearly, a lens termed a "T lens" is a lens designed for use with a T type camera. Hence, the height, the width and the diagonal of the sensor with which it is usually used is given, even if not all members might know the exact measures; I, for one, don't know them but I know where I can look them up.  When using a T lens on an SL body, no cropping takes place as the sensor of the SL is taller and wider than the image projected by the T lens. This is the reason why some people don't use the term "crop" for the use of a lens with a sensor which is larger than the reference. Other people use the term "crop" as if it meant "ratio" and they will arive at "crop" factors which are smaller than one.  However, in the particular case of a T lens being used on an SL, the camera takes into account that the T lens projects an image which is smaller than its sensor. If I understand the specification of the camera, the SL will  only use the part of its sensor which has the same dimensions as the T's.  In  terms of this discussion, I would say that the crop factor was 1, meaning that no cropping took place. Others would argue that the T camera had a crop factor c>1 and therefore a T lens when used on an SL would have the same crop factor c>1. But then, that crop factor c>1 would apply to FF lenses when used on the T body and not to the T lenses when used on a FF body. Link to post Share on other sites More sharing options...
pop Posted October 30, 2015 Share #45  Posted October 30, 2015 Not when we calculate CoC, pop. You're perfectly right there, but the question under discussion here with the answer supplied concerned itself with the FOV only. Link to post Share on other sites More sharing options...
pop Posted October 30, 2015 Share #46  Posted October 30, 2015  In any case, neither the original question nor the answer were well formulated because they used the "unspecified" variable Please refer to the original question  and answer.  The question asked for the "crop ratio" when using an S lens on an SL body. The dimensions of the sensor of the Leica S are both specified and publicly documented. So are the dimensions of the sensor of the Leica SL. Michael quoted the question when supplying the answer, thus making it quite clear which kind of lens and which kind of body the answer applied to.  So, please tell where an "unspecified" value comes into play here. Link to post Share on other sites More sharing options...
lct Posted October 30, 2015 Share #47 Â Posted October 30, 2015 Advertisement (gone after registration) You're perfectly right there, but the question under discussion here with the answer supplied concerned itself with the FOV only. I won't insist ad nauseam but as far as FoV is concerned, one can hardly say that both 'Blad and M8 have the same crop factor.. Link to post Share on other sites More sharing options...
pop Posted October 30, 2015 Share #48 Â Posted October 30, 2015 I won't insist ad nauseam but as far as FoV is concerned, one can hardly say that both 'Blad and M8 have the same crop factor.. I agree, but then, who here says that a Hasselblad has the same crop factor as an M8? Link to post Share on other sites More sharing options...
LocalHero1953 Posted October 30, 2015 Share #49  Posted October 30, 2015 Just woken up. WTF? At least this is now a separate thread. But 3 pages? When I suspect most people here are perfectly clear about crop factors in the real world. This is just the deer rutting season. Link to post Share on other sites More sharing options...
lct Posted October 30, 2015 Share #50 Â Posted October 30, 2015 I agree, but then, who here says that a Hasselblad has the same crop factor as an M8? You, sort of... . If you say that the S has a 1.2x factor, then the Blad has 1.3x like the M8... Link to post Share on other sites More sharing options...
pop Posted October 30, 2015 Share #51 Â Posted October 30, 2015 You, sort of... . If you say that the S has a 1.2x factor, then the Blad has 1.3x like the M8... I think you must have mistaken another member's post for mine. I don't think I even mentioned a single crop factor within this thread. Those particular comparisons are wrong in every which way. Link to post Share on other sites More sharing options...
lct Posted October 30, 2015 Share #52  Posted October 30, 2015 I thought you were supporting the 1.2x camp here sorry... Link to post Share on other sites More sharing options...
Daedalus2000 Posted October 30, 2015 Author Share #53  Posted October 30, 2015 I don't see where any confusion should come from.  Clearly, a lens termed a "T lens" is a lens designed for use with a T type camera. Hence, the height, the width and the diagonal of the sensor with which it is usually used is given, even if not all members might know the exact measures; I, for one, don't know them but I know where I can look them up.  When using a T lens on an SL body, no cropping takes place as the sensor of the SL is taller and wider than the image projected by the T lens. This is the reason why some people don't use the term "crop" for the use of a lens with a sensor which is larger than the reference. Other people use the term "crop" as if it meant "ratio" and they will arive at "crop" factors which are smaller than one.  However, in the particular case of a T lens being used on an SL, the camera takes into account that the T lens projects an image which is smaller than its sensor. If I understand the specification of the camera, the SL will  only use the part of its sensor which has the same dimensions as the T's.  In  terms of this discussion, I would say that the crop factor was 1, meaning that no cropping took place. Others would argue that the T camera had a crop factor c>1 and therefore a T lens when used on an SL would have the same crop factor c>1. But then, that crop factor c>1 would apply to FF lenses when used on the T body and not to the T lenses when used on a FF body.  Ok, so you say that the crop factor of a T lens on the S lens is 1... That is what I expected and as you say most people will not see this way.  I will not continue this discussion because I do not think it helps anyone, but one last point I will make is that having a reference sensor that we all understand makes things much simpler. Say for example you have an S camera and one gives you a Hasselblad lens. Using the way of thinking that you support means that I need to know the exact dimensions of the Hasselblad system this lens was constructed for. I do not know of the top of my head what these dimensions are, so I can not calculate the field of view...  The approach that uses the 35mm FF sensor as the reference does not need to know that. All I need to know is that my S has a crop factor or 0.8 vs the 35mm FF sensor, the lens say has a focal length of 110, so it will be have an equivalent FOV as a 88mm on the 35mm FF sensor. Simple.  Thanks for the discussion. Link to post Share on other sites More sharing options...
pop Posted October 30, 2015 Share #54 Â Posted October 30, 2015 (...) Say for example you have an S camera and one gives you a Hasselblad lens. (...) In that case you need to know two things: one is the field of view a particular focal length will produce on your camera. Since presumably you have used your camera for some time, you will be able to tell whether a lens with a particular focal length will qualify as a wide angle or a tele lens on your camera. If you express that in crop factors, you're welcome. The other thing is whether the lens will be able to produce an image which covers all of the sensor at a reasonable image quality. In order to know that, you'd have to know the image format the lens was designed for. These are effectively the data you said above that you can not know off the top of your head. Â The "crop factor" for using T lenses on the SL is insofar problematic to express as there is no cropping involved, only unusable or unused real estate on the sensor. That's the opposite of a crop. if I crop a piece of paper, it has never in all my life happened to become taller or wider by cropping. Link to post Share on other sites More sharing options...
lct Posted October 30, 2015 Share #55 Â Posted October 30, 2015 As i said above, why doing simple... Link to post Share on other sites More sharing options...
Daedalus2000 Posted October 30, 2015 Author Share #56  Posted October 30, 2015 In that case you need to know two things: one is the field of view a particular focal length will produce on your camera. Since presumably you have used your camera for some time, you will be able to tell whether a lens with a particular focal length will qualify as a wide angle or a tele lens on your camera. If you express that in crop factors, you're welcome. The other thing is whether the lens will be able to produce an image which covers all of the sensor at a reasonable image quality. In order to know that, you'd have to know the image format the lens was designed for. These are effectively the data you said above that you can not know off the top of your head.  The "crop factor" for using T lenses on the SL is insofar problematic to express as there is no cropping involved, only unusable or unused real estate on the sensor. That's the opposite of a crop. if I crop a piece of paper, it has never in all my life happened to become taller or wider by cropping.  Do I have to own and use a camera to be able to calculate the fov for a particular lens on it? That will be very expensive! :-)  I think the main assuption is that most people understand the 35mm fov and that is why is used as a reference and any other camera's fov is discussed in equivalent terms without needing to own it.  Very best, D Link to post Share on other sites More sharing options...
pop Posted October 30, 2015 Share #57 Â Posted October 30, 2015 Do I have to own and use a camera to be able to calculate the fov for a particular lens on it? That will be very expensive! :-) Well, no, it's the other way 'round. If you own and use a camera, you presumably know which focal length is the 'normal' one for that camera. Link to post Share on other sites More sharing options...
CheshireCat Posted October 30, 2015 Share #58  Posted October 30, 2015 Please refer to the original question  and answer.  The question asked for the "crop ratio" when using an S lens on an SL body. The dimensions of the sensor of the Leica S are both specified and publicly documented. So are the dimensions of the sensor of the Leica SL. Michael quoted the question when supplying the answer, thus making it quite clear which kind of lens and which kind of body the answer applied to.  So, please tell where an "unspecified" value comes into play here.  The unspecified value is the reference sensor. Like I said in a previous post, there are two answers for the original question, one for each possible value of the "unspecified" parameter:   - The crop ratio with respect to a full-frame sensor is 1.  - The crop ratio with respect to the S sensor is 1.25.   Corollary: A question that has two answers is not well formulated, and a single answer to that question is not well formulated either. And the 3 thread pages of useless arguing stem from the fact the question is not well formulated.  But don't worry, you and Michael are right when you say that the crop ratio is 1.25... but sorry, you are also wrong, because the crop ratio is also 1 Link to post Share on other sites More sharing options...
CheshireCat Posted October 30, 2015 Share #59  Posted October 30, 2015 However, in the particular case of a T lens being used on an SL, the camera takes into account that the T lens projects an image which is smaller than its sensor. If I understand the specification of the camera, the SL will  only use the part of its sensor which has the same dimensions as the T's.  In  terms of this discussion, I would say that the crop factor was 1, meaning that no cropping took place. Others would argue that the T camera had a crop factor c>1 and therefore a T lens when used on an SL would have the same crop factor c>1. But then, that crop factor c>1 would apply to FF lenses when used on the T body and not to the T lenses when used on a FF body.  Look, pop, it is not rocket science...  With respect to a full-frame sensor: 1) If the SL with a T lens crops the frame in post to match the T sensor size, then the resulting shot will have a crop-factor of 1.5. 2) If the SL with a T lens does not crop the frame, then the resulting shot will have a crop-factor of 1 (and horrible black vignetting in the corners). The actual FOV will be limited by the lens projection circle. If you then use photoshop to crop that shot, then the crop factor of the resulting image will be higher than 1.  Your confusion is caused by the fact that you think the crop-factor is also a property of the lens, while it is just a property of the resulting image. Whether the sensor is cropping the image, or firmware, or you with Photoshop... it really does not matter. Link to post Share on other sites More sharing options...
pop Posted October 30, 2015 Share #60 Â Posted October 30, 2015 Look, pop, it is not rocket science... Thanks for trying. It's a nice try. I agree that it's not rocket science. It's about the meaning of terms. Â Anyway, those who have not understood by now are not likely to do so in the further course of this thread. Link to post Share on other sites More sharing options...
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