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Apeture affecte from fulframe too APSC ?


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Register and DoF are basic stuffs indeed. I suspect Jaap will give you a basic lesson :D

I look forward to reading it and how the adapter magically works. Should be fascinating.

 

Btw, ever look at various lens adapters and wonder how they work on various cameras? You can stack them too!!! Wow! Changes even further the distance from the lens to the sensor. How do you think that works??? Somehow, can still focus. Those rings must be really smart.

Edited by Belle123
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Huh???

Every adaptor, extender, etc., puts a lens at a little different distance from the sensor, or film, and there is no correction. Obviously you don’t have an M to TL Mount adapter. There is no lens in the adapter. And the camera itself makes no correction in focus. The way focus works is adjustment of distance within the lens. Take an M lens and move around the focus ring and see what happens. It moves? Magic. The camera itself has nothing to do with focusing. It’s the lens. This is basic stuff.

You are reading something into that that Jaap did not say.  And while Jaap may or may not have an M to TL adapter I certainly do.  The adapter takes an M lens, which is intended to attach to the surface of an M camera, approximately 27mm from the imaging chip (that's the register distance) and places it about 6 mm out from the opening of the CL or SL, which have a register distance of 21mm.  That way the distance from lens parts to the chip is preserved.  Once that is accomplished the relationship between lens and sensor is as before, but the sensor is smaller in an APS-C camera than in a full frame.  So every adapter (including those for R, S, and Sony lens mounts) places a lens at its correct distance from the image that it forms in the camera.  And perhaps you did not detect any DOF change when the images were aligned at the same size, but others have.

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You are reading something into that that Jaap did not say.  And while Jaap may or may not have an M to TL adapter I certainly do.  The adapter takes an M lens, which is intended to attach to the surface of an M camera, approximately 27mm from the imaging chip (that's the register distance) and places it about 6 mm out from the opening of the CL or SL, which have a register distance of 21mm.  That way the distance from lens parts to the chip is preserved.  Once that is accomplished the relationship between lens and sensor is as before, but the sensor is smaller in an APS-C camera than in a full frame.  So every adapter (including those for R, S, and Sony lens mounts) places a lens at its correct distance from the image that it forms in the camera.  And perhaps you did not detect any DOF change when the images were aligned at the same size, but others have.

Clearly, he was meaning focus. And you can stack these, which totally blows your explanation out of the water.

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Let me back track a little with better explanation.

Every lens has a minimum distance it needs to be from either film or sensor to focus. Agreed?

If the distance from the sensor to an M lens is same on on M camera as is using converter for M to T, all would be equal except for field of view the sensor can handle. period. DOF would not change.

But I don’t know if my M to T adapter is exactly that minimum distance. It might be slightly more. So, that might explain any changes.

As long as you have minimum distance covered with conversion rings, a lens can focus. But to make broad statement that the conversion ring corrects, not quite correct. It corrects minimum distance but can go out further.

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I have watched the video and as I understand it, he says that a 35mm f2 FF put on an APSC sensor isn't really an F2 lens anymore...since the lens + sensor combination does affect the amount of light the lens can gather.

That is the reason why, when he compares FF and APSC he says that a 35mm f2 becomes when used with a APSC sensor a 50mm f2.8 equivalent lens for both DOF and light gathering.That is the reason why he explains that to keep the same brightness/exposure equivalence between the 35mm on FF and this same 35mm in APSC you should raise the iso more on the APSC to compensage for the light loss.

Am I correct in this ?

This video confuses what I thought to be true, I mean I thought the light gathering was retained...but it seems this is not true if you take into account the smaller sensor.

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Clearly, he was meaning focus. And you can stack these, which totally blows your explanation out of the water.

You  are not making sense, and I guess I cannot help.  I'll let Jaap try.  Is there a video somewhere that has started all this confusion?

Edited by scott kirkpatrick
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[...] If the distance from the sensor to an M lens is same on on M camera as is using converter for M to T, all would be equal except for field of view the sensor can handle. period. DOF would not change [...]

 

DoF will change because there are two factors for it, among others: sensor size (or CoC value to be more accurate) and subject distance. If you change one or both factors, you change DoF necessarily. Easy to check with a DoF calculator (http://www.dofmaster.com/dofjs.html).

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who invented the crop factor should be sentenced forever

 

there is no multiplier for focal lenght, there is no effective aperture existing only a given, there is nothing magic, only marketing

 

the physical specs of a given lens does not change by holding something different behind it, it may be a  film, a sensor or a toilet

 

DOF is given by construction and aperture. If DOF changes because distance to subject changed, to get the same picture on another format of sensor the lens still has no effective aperture, it is a matter of composition.  If you keep the subject distance, that DOF remains, you only get a wider or narrower angle of view...and this is exacly the only difference...angle of view should be the the naming instead of crop.

 

@ belle123...study about register of a lens and you will understand thickness of adaptors and what  can be combined or not...if they are too numerous they are called macro rings :-)

Edited by thomasstellwag
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I have watched the video and as I understand it, he says that a 35mm f2 FF put on an APSC sensor isn't really an F2 lens anymore...since the lens + sensor combination does affect the amount of light the lens can gather.

That is the reason why, when he compares FF and APSC he says that a 35mm f2 becomes when used with a APSC sensor a 50mm f2.8 equivalent lens for both DOF and light gathering.That is the reason why he explains that to keep the same brightness/exposure equivalence between the 35mm on FF and this same 35mm in APSC you should raise the iso more on the APSC to compensage for the light loss.

Am I correct in this ?

This video confuses what I thought to be true, I mean I thought the light gathering was retained...but it seems this is not true if you take into account the smaller sensor.

Edited by Kim Dahl
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I have watched the video and as I understand it, he says that a 35mm f2 FF put on an APSC sensor isn't really an F2 lens anymore...since the lens + sensor combination does affect the amount of light the lens can gather.

That is the reason why, when he compares FF and APSC he says that a 35mm f2 becomes when used with a APSC sensor a 50mm f2.8 equivalent lens for both DOF and light gathering.That is the reason why he explains that to keep the same brightness/exposure equivalence between the 35mm on FF and this same 35mm in APSC you should raise the iso more on the APSC to compensage for the light loss.

Am I correct in this ?

This video confuses what I thought to be true, I mean I thought the light gathering was retained...but it seems this is not true if you take into account the smaller sensor.

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Hello.

That's also how I saw the video.

That it would not reach as much light too an APSC censor like an FF. So 1.4 is realy not 1.4

That is, it is a summilux on APSC but not a summilux in FF. In mathematics I know you can not change a factor and get the same result without too chance en other Factor.

For new readers, please see the video first in the thread.

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If that video has generated this much misinformation, I think I will skip it.  If you set your CL for ISO 100, and put a 35/1.4 lens on it and find that an exposure of f/8 at 1/400 works, I assure you that the exposure with a 35mm lens on an M at ISO 100 will also be f/8 at 1/400.  The same is true if both lenses are at f/1.4, although we may have to find an indoor scene where, say f/1.4 at 1/125 sec works for both cameras.  Exposure doesn't change with focal length or field of view.

Edited by scott kirkpatrick
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who invented the crop factor should be sentenced forever

 

there is no multiplier for focal lenght, there is no effective aperture existing only a given, there is nothing magic, only marketing

 

the physical specs of a given lens does not change by holding something different behind it, it may be a  film, a sensor or a toilet

 

DOF is given by construction and aperture. If DOF changes because distance to subject changed, to get the same picture on another format of sensor the lens still has no effective aperture, it is a matter of composition.  If you keep the subject distance, that DOF remains, you only get a wider or narrower angle of view...and this is exacly the only difference...angle of view should be the the naming instead of crop.

 

@ belle123...study about register of a lens and you will understand thickness of adaptors and what  can be combined or not...if they are too numerous they are called macro rings :-)

Not if you keep the field of view identical, which most people do. Then you to alter the subject distance and then the DOF will change.

DOF is an illusion anyway, created by the resolution of our eyes. Change you spectacles prescription and the DOF on all your images will change,

A photograph is only sharp in the plane of focus, and nowhere else.

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Let me back track a little with better explanation.

Every lens has a minimum distance it needs to be from either film or sensor to focus. Agreed?

If the distance from the sensor to an M lens is same on on M camera as is using converter for M to T, all would be equal except for field of view the sensor can handle. period. DOF would not change.

But I don’t know if my M to T adapter is exactly that minimum distance. It might be slightly more. So, that might explain any changes.

As long as you have minimum distance covered with conversion rings, a lens can focus. But to make broad statement that the conversion ring corrects, not quite correct. It corrects minimum distance but can go out further.

?????

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Let me back track a little with better explanation.

Every lens has a minimum distance it needs to be from either film or sensor to focus. Agreed?

If the distance from the sensor to an M lens is same on on M camera as is using converter for M to T, all would be equal except for field of view the sensor can handle. period. DOF would not change.

But I don’t know if my M to T adapter is exactly that minimum distance. It might be slightly more. So, that might explain any changes.

As long as you have minimum distance covered with conversion rings, a lens can focus. But to make broad statement that the conversion ring corrects, not quite correct. It corrects minimum distance but can go out further.

 

Let me modify this a bit...

 

*Every CAMERA with interchangeable lenses has a set flange (sensor to lens mount) distance. Lenses designed for a system are done so in a way that allows them to focus throughout their entire range when mounted at that flange distance.

*If you want to mount the lens on a camera with a different flange distance you'll need to find a way to get that lens the same distance from the sensor plane as it would be on it's native system. That's what the adaptors do.

*If you change the flange difference from what the lens requires then the adapted lens will no longer be able to focus throughout its entire normal range. For example, if you INCREASE the flange distance on a lens you can focus closer but will lose infinity focus. (macro rings). SO you can just have a minimum and not worry about making an adaptor too long.

*Apparent (note the use of the word apparent) DoF changes because a smaller sensor needs more enlargement to reach a certain viewing size. Your doing that by moving from an M to TL.

*Your M to T adaptor isn't exactly the right size. It should be, in an ideal world however manufacturers make them a tiny bit short to guarantee infinity focusing. And if there's an issue with tolerances or thermal expansion and the adaptor becomes longer you'd lose infinity focus.

 

Gordon

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The use of smaller than FF sensors determines both apparent and calculated DoF changes as we know it since the first APS and small sensor digital cameras. Just for info, Sony allows to reduce the MFD of M lenses w/o losing infinity focus by way of adapters with focusing helicoid like Voigtlander V-ME close focus adapter. Apparent and calculated DoF do change then due to the reduced subject distance accordingly. 

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Not if you keep the field of view identical, which most people do. Then you to alter the subject distance and then the DOF will change.

DOF is an illusion anyway, created by the resolution of our eyes. Change you spectacles prescription and the DOF on all your images will change,

A photograph is only sharp in the plane of focus, and nowhere else.

but this is exactly what I wrote..changing the subject distance is no physics of the lens it is composition....

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