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Old Mar 17, 2007, 5:27 PM   #21
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Hayward wrote:
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Could also be the 62-55mm step down factor mismatch I suppose, especially if wide open. (vs it on a matched lens)
Hi Hayward,

The front element of the Tcon is @77mm (just eyeballed it, didn't measure) This will relate more to light gathering than the exit pupil of the Tcon. It is designed to not compromise the amount of light entering the lens -- relative max aperture -- regardless of the diameter of the lens it's mounted on.

Scott


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Old Mar 17, 2007, 6:02 PM   #22
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snostorm wrote:
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Hayward wrote:
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Could also be the 62-55mm step down factor mismatch I suppose, especially if wide open. (vs it on a matched lens)
Hi Hayward,

The front element of the Tcon is @77mm (just eyeballed it, didn't measure) This will relate more to light gathering than the exit pupil of the Tcon. It is designed to not compromise the amount of light entering the lens -- relative max aperture -- regardless of the diameter of the lens it's mounted on.

Scott

then how do you explain my cameras auto exposure setting it to a slower shutter speed with the TC on?
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Old Mar 17, 2007, 6:52 PM   #23
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Hi xfxgeforced,


I'm assuming that you used matrix or center-weighted metering. With the Tcon, the FOV is smaller and does not contain all the elements of the wider shot, in this case, the band of dried grass (?) that shows as a beige streak in the background for example. The only way that you would get the same exposure settings would be to capture the same frame. Try this -- Take consecutive shots of the same section of a cloudless sky with and without the Tcon. Since there will be no difference in the elements in the frame, you will probably find that the exposure value doesn't change significantly. Another way to test this would be to use spot metering on the middle of the stop sign in your example. I could be wrong, but I never noticed any significant loss of light when using the Tcon 17, certainly not anything near a full stop.

Also, depending on the time of day, the overall exposure value of a scene can change significantly in minutes. Your eyes do a magnificent job of instantaneously adjusting for that, and you might not see it, but the camera knows, and will adjust the exposure accordingly.

Scott
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Old Mar 17, 2007, 7:47 PM   #24
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snostorm wrote:
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Hi xfxgeforced,


I'm assuming that you used matrix or center-weighted metering. With the Tcon, the FOV is smaller and does not contain all the elements of the wider shot, in this case, the band of dried grass (?) that shows as a beige streak in the background for example. The only way that you would get the same exposure settings would be to capture the same frame. Try this -- Take consecutive shots of the same section of a cloudless sky with and without the Tcon. Since there will be no difference in the elements in the frame, you will probably find that the exposure value doesn't change significantly. Another way to test this would be to use spot metering on the middle of the stop sign in your example. I could be wrong, but I never noticed any significant loss of light when using the Tcon 17, certainly not anything near a full stop.

Also, depending on the time of day, the overall exposure value of a scene can change significantly in minutes. Your eyes do a magnificent job of instantaneously adjusting for that, and you might not see it, but the camera knows, and will adjust the exposure accordingly.

Scott
i took multiple shots at different times in each way, and at first i had the tcon on, looking at the slow sign, then i moved up with no tcon to get the same framing, and still had that. Thanks for the suggestions
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Old Mar 18, 2007, 12:23 AM   #25
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Just ordered this lens from Adorama, also ordered a UV filter for it, and my Takumar 28-80 MM. Hopefully the weather will be nice next weekend and I can get out and take a few shots with it.

I went to a local shop < Schillers, XFX will know about them > and checked it out today. It seemed to be a darn nice lens, focus seemed fast and accurate, and for it's size, it is quite light weight.
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Old Mar 18, 2007, 1:03 AM   #26
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StevePMo wrote:
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Just ordered this lens from Adorama, also ordered a UV filter for it, and my Takumar 28-80 MM. Hopefully the weather will be nice next weekend and I can get out and take a few shots with it.

I went to a local shop < Schillers, XFX will know about them > and checked it out today. It seemed to be a darn nice lens, focus seemed fast and accurate, and for it's size, it is quite light weight.
actually, ive never heard of that place, but what street is it on? if prices arent way unreasonable, ill check them out. They sell used lenses?
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Old Mar 18, 2007, 1:15 AM   #27
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Schillers is on Manchester, Just east of McNight < less than a half mile > and yes, they sell used lenses, flashes, etc. They were asking $199 for the Tamron 70-300, i got it for 163.99 from Adorama
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Old Mar 18, 2007, 1:18 AM   #28
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StevePMo wrote:
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Schillers is on Manchester, Just east of McNight < less than a half mile > and yes, they sell used lenses, flashes, etc. They were asking $199 for the Tamron 70-300, i got it for 163.99 from Adorama
yeah, the only good b&m deals are used
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Old Mar 18, 2007, 2:41 AM   #29
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snostorm wrote:
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The front element of the Tcon is @77mm (just eyeballed it, didn't measure) This will relate more to light gathering than the exit pupil of the Tcon
Light is a PHYSICAL partical and behaves as such.

Yes you can have a BILLION partical inlet ..... but only a 1000 particalcal exit.... many of those billion are going to get lost/wait in line.

Like water through a nozzle... vs just the hose with none...maybe higher concentrated preasure when restricted.... but only so much water/particles get out... and never more than the input (meaning 55mm exit to a 62mm input) So a 62mm lens is going to be seeing low pressure from a just 55mm source.

Again how big the front does not matter if the exit is not matched to the next input.

Yes on a 55mmm Lens.... maybe little loss but you are severely stepping down..... really surprised they are seeing no vignetting at the 70mm end of the zoom... then yes something is likely to happen.

I will guaranttee you the exposure of that TCON on a matched (55 to 55m ) lens is going to be hiigher/faster.... than a severely stepped down one..... usually 3mm is a standard acceptable max for step down before before there begining to be noticeable impacts, especial wide FL (if zoom) and/or wide open on the receiving lens.


The ultimate example is the non lens.... a pinhole camera.... very sharp image potentially... but requires intense light or a very long exposure.






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Old Mar 18, 2007, 9:45 PM   #30
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waves in the electromagnetic spectrum can only travel in space because they are made up of particles called photons, which means they don't need an outside medium to travel in, like a sound (pressure) wave.
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