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#1
January 30th 05, 07:54 PM
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2X or 1.4X converters on DSLRs, and the 'crop factor'
Another poster has asked about a 2X Quantaray converter on a zoom
lens. Many people in the 35mm film arena suggest never using more than a 1.4X converter because any imperfections in the lens (and the converter) are magnified, along with losses in contrast, saturation, and so on. If a DSLR already has a 'crop factor' of, say, 1.5 is the lens already stressed to its maximum? Does the crop factor have the same effect on lens quality as putting a converter on the lens for a 35mm film camera? -- Phil Stripling | email to the replyto address is presumed The Civilized Explorer | spam and read later. email from this URL http://www.cieux.com/ | http://www.civex.com/ is read daily. 
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#2
January 30th 05, 08:02 PM
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Many people in the 35mm film arena suggest never using=AD more than a
1.4X converter because any imperfections in the lens (and th=ADe converter) are magnified, along with losses in contrast, saturation, an=ADd so on. Good advice for cheap lenses, but with high quality lenses and matched t/c's you still get good results. We use a 2x with a 500 f/4 L IS often and the image quality is very high, but the lens is very expensive. With even a 100-400 L IS lens I'd expect poor results. If a DSLR already has a 'crop factor' of, say, 1.5 is the le=ADns already stressed to its maximum? Does the crop factor have the same =ADeffect on lens quality as putting a converter on the lens for a 35mm film c=ADamera? The 'crop factor' means you are using the sweet spot of the lens, cropping off the edges where most problems show up, so it's the opposite of what you say. Bill
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#3
January 30th 05, 08:32 PM
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"Phil Stripling" wrote in message
... Another poster has asked about a 2X Quantaray converter on a zoom lens. Many people in the 35mm film arena suggest never using more than a 1.4X converter because any imperfections in the lens (and the converter) are magnified, along with losses in contrast, saturation, and so on. If a DSLR already has a 'crop factor' of, say, 1.5 is the lens already stressed to its maximum? Does the crop factor have the same effect on lens quality as putting a converter on the lens for a 35mm film camera? -- Phil Stripling | email to the replyto address is presumed The Civilized Explorer | spam and read later. email from this URL http://www.cieux.com/ | http://www.civex.com/ is read daily. Another reason to use a 1.4 rather than a 2x is that Canon's less than top line cameras, film and digital, won't autofocus at a max aperture of less than f5.6. A 2x on an f2.8 lens gets you that, a 1.4x on an f4 lens stays within limits, but a 2x on an f5.6 lens may have problems. With a Canon telelconverter, it won't AF, with an after market converter, you may have metering problems, since those converters tell the camera that it's really at f5.6, so you might end up underexposed by a stop or more. You can always crank in some EC, of course. -- Skip Middleton http://www.shadowcatcherimagery.com
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#4
January 30th 05, 10:16 PM
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In article , Phil Stripling
wrote: Another poster has asked about a 2X Quantaray converter on a zoom lens. Many people in the 35mm film arena suggest never using more than a 1.4X converter because any imperfections in the lens (and the converter) are magnified, along with losses in contrast, saturation, and so on. If a DSLR already has a 'crop factor' of, say, 1.5 is the lens already stressed to its maximum? Does the crop factor have the same effect on lens quality as putting a converter on the lens for a 35mm film camera? Well, using teleconverters is never going to improve the quality.
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#5
January 31st 05, 01:33 AM
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The amount of image degradation will be the same. You are simply using
less of the image circle, and if there is any change n effect al all it would be that the digital is using less of the circle's edge which is never as good as the center anyway. -- http://www.chapelhillnoir.com home of The Camera-ist's Manifesto The Improved Links Pages are at http://www.chapelhillnoir.com/links/mlinks00.html A sample chapter from "Haight-Ashbury" is at http://www.chapelhillnoir.com/writ/hait/hatitl.html "Phil Stripling" wrote in message ... Another poster has asked about a 2X Quantaray converter on a zoom lens. Many people in the 35mm film arena suggest never using more than a 1.4X converter because any imperfections in the lens (and the converter) are magnified, along with losses in contrast, saturation, and so on. If a DSLR already has a 'crop factor' of, say, 1.5 is the lens already stressed to its maximum? Does the crop factor have the same effect on lens quality as putting a converter on the lens for a 35mm film camera? -- Phil Stripling | email to the replyto address is presumed The Civilized Explorer | spam and read later. email from this URL http://www.cieux.com/ | http://www.civex.com/ is read daily.
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#6
February 1st 05, 11:39 PM
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In message .com,
"Bill Hilton" wrote: Many people in the 35mm film arena suggest never using?more than a 1.4X converter because any imperfections in the lens (and th? converter) are magnified, along with losses in contrast, saturation, an? so on. Good advice for cheap lenses, but with high quality lenses and matched t/c's you still get good results. We use a 2x with a 500 f/4 L IS often and the image quality is very high, but the lens is very expensive. With even a 100-400 L IS lens I'd expect poor results. I've taken shots with my 100-400 and a Tamron 2x that were sharp enough, though not spectacular. It usually involves stopping down, though. With a D30 the 2x might do a lot better. If a DSLR already has a 'crop factor' of, say, 1.5 is the le?s already stressed to its maximum? Does the crop factor have the same ?ffect on lens quality as putting a converter on the lens for a 35mm film c?mera? The 'crop factor' means you are using the sweet spot of the lens, cropping off the edges where most problems show up, so it's the opposite of what you say. .... but you still are cutting the lens' resolution per frame height or width by 33% with a 1.5x crop. The corners may be worse, full-frame, if the quality dropoff at the corners is dramatic (more than 1.5x worse than the corners of the crop). People seem to forget this fact in this type of discussion. -- John P Sheehy
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#7
February 1st 05, 11:43 PM
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In message ,
Randall Ainsworth wrote: In article , Phil Stripling wrote: Another poster has asked about a 2X Quantaray converter on a zoom lens. Many people in the 35mm film arena suggest never using more than a 1.4X converter because any imperfections in the lens (and the converter) are magnified, along with losses in contrast, saturation, and so on. If a DSLR already has a 'crop factor' of, say, 1.5 is the lens already stressed to its maximum? Does the crop factor have the same effect on lens quality as putting a converter on the lens for a 35mm film camera? Well, using teleconverters is never going to improve the quality. Yes they can, Archie. If you have a lens that is sharper than the sensor (or film grain) can resolve, then a teleconverter will capture more detail. I don't expect you to be able to comprehend this. -- John P Sheehy
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#8
February 19th 05, 09:25 PM
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Skip M wrote:
Another reason to use a 1.4 rather than a 2x is that Canon's less than top line cameras, film and digital, won't autofocus at a max aperture of less than f5.6. A 2x on an f2.8 lens gets you that, a 1.4x on an f4 lens stays within limits, but a 2x on an f5.6 lens may have problems. With a Canon telelconverter, it won't AF, with an after market converter, you may have metering problems, since those converters tell the camera that it's really at f5.6, so you might end up underexposed by a stop or more. No, it shouldn't. After the 2x, f/5.6 becomes effectively f/11. Even though the converter doesn't tell the camera about this, and the camera still assumes f/5.6, the light passes through f/11 effective. So the meter sees less light. It does not need to know that it's because f/5.6 changed to f/11, but just concludes that the light gets dimmer and sets the correct shutter speed and/or sensitivity.
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#9
February 20th 05, 05:46 AM
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wrote in message
oups.com... Skip M wrote: Another reason to use a 1.4 rather than a 2x is that Canon's less than top line cameras, film and digital, won't autofocus at a max aperture of less than f5.6. A 2x on an f2.8 lens gets you that, a 1.4x on an f4 lens stays within limits, but a 2x on an f5.6 lens may have problems. With a Canon telelconverter, it won't AF, with an after market converter, you may have metering problems, since those converters tell the camera that it's really at f5.6, so you might end up underexposed by a stop or more. No, it shouldn't. After the 2x, f/5.6 becomes effectively f/11. Even though the converter doesn't tell the camera about this, and the camera still assumes f/5.6, the light passes through f/11 effective. So the meter sees less light. It does not need to know that it's because f/5.6 changed to f/11, but just concludes that the light gets dimmer and sets the correct shutter speed and/or sensitivity. Really, I wouldn't have thunk it... -- Skip Middleton http://www.shadowcatcherimagery.com
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