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12-10-2013, 08:25 AM   #1
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Apc to ff lens adapter

Is it possible to create an adapter for apc lenses that will "boost" their coverage area to an ff lens level? If metabones booster can boost aperture why not boost an coverage?

12-10-2013, 08:51 AM   #2
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Yes. It's called a "teleconverter":

Teleconverter - Wikipedia, the free encyclopedia

"For example, a 2× teleconverter for a 35 mm camera enlarges the central 12×18 mm part of an image to the size of 24×36 mm in the standard 35 mm film format."
12-10-2013, 08:54 AM   #3
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I think what he is asking is if there is an adapter to enlarge the reduced image circle fo DA lenses to cover full frame. With a teleconverter, say a 2x on a 21mm you would effectively have a 42mm lens. If you could just enlarge the image circle, it would still act as a 21.

Last edited by Parallax; 12-10-2013 at 09:01 AM.
12-10-2013, 09:07 AM   #4
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QuoteOriginally posted by Parallax Quote
I think what he is asking is if there is an adapter to enlarge the reduced image circle fo DA lenses to cover full frame. With a teleconverter, say a 2x on a 21mm you would effectively have a 42mm lens. If you could just enlarge the image circle, it would still act as a 21.
exactly

12-10-2013, 09:13 AM   #5
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A teleconverter is just the opposite of the "metabones booster" mentioned in the original post.

Here's another explanation which may be helpful:

LensRentals.com - Metabones Magic?

"A teleconverter spreads out the light leaving the lens so that only the center portion reaches the sensor. The result is the focal length of the lens seems longer (the image is magnified), but at the cost of reducing the amount of light (effective aperture) of the lens. The Speed Booster compresses the light leaving the lens onto a smaller image circle. This makes the focal length seem shorter and actually increases the amount of light reaching the sensor."
12-10-2013, 09:18 AM   #6
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QuoteOriginally posted by Parallax Quote
I think what he is asking is if there is an adapter to enlarge the reduced image circle fo DA lenses to cover full frame. With a teleconverter, say a 2x on a 21mm you would effectively have a 42mm lens. If you could just enlarge the image circle, it would still act as a 21.
Wish I had a film camera sitting here to try it, but what he said makes sense. A 2x teleconverter would be effectively spreading the image circle out to twice its original size… that's part of why it doubles the aperture and makes everything darker. And if you used one that was originally for film/full frame, there shouldn't be anything stopping it from making a crop lens cover a full frame or film sensor, right?
12-10-2013, 09:46 AM   #7
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QuoteOriginally posted by narual Quote
there shouldn't be anything stopping it from making a crop lens cover a full frame or film sensor, right?
Right, but it would be a different effective focal length. Another example would be to compare a DA 35mm and an FA 35. The DA 35 with a 2x converter will certainly, AFAIK, cover full frame and the image will be the same as you would get with a 70mm lens. If you could simply enlarge the image circle of the DA lens to cover FF, as the OP has confirmed he is inquiring about, it would give you the same image as the FA 35 would without the teleconverter. I think there would be an penalty from from such a device though because, as with a teleconverter, you would be spreading the same of transmitted light over a larger area so it would still require a different exposure.
12-10-2013, 10:14 AM   #8
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QuoteOriginally posted by Parallax Quote
Right, but it would be a different effective focal length. Another example would be to compare a DA 35mm and an FA 35. The DA 35 with a 2x converter will certainly, AFAIK, cover full frame and the image will be the same as you would get with a 70mm lens. If you could simply enlarge the image circle of the DA lens to cover FF, as the OP has confirmed he is inquiring about, it would give you the same image as the FA 35 would without the teleconverter. I think there would be an penalty from from such a device though because, as with a teleconverter, you would be spreading the same of transmitted light over a larger area so it would still require a different exposure.
Of course it would, you're using a teleconverter. The metabones thing also gives a different effective focal length, making the lens wider. It's basically a ~.7x teleconverter, right? Turns a 50 f/2 into an effective 35 f/1.4 and so on?

12-10-2013, 10:28 AM   #9
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QuoteOriginally posted by narual Quote
It's basically a ~.7x teleconverter, right? Turns a 50 f/2 into an effective 35 f/1.4 and so on?
Yes, but he doesn't want it to be an "effective" anything. He wants a 50 to be a 50 and a 35 to be a 35, but cover a FF sensor, but as I said, even if it can be done to retain original FL, there will be an exposure penalty.
12-10-2013, 10:45 AM   #10
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He also was referencing metabones, which does change it.

Anyway -- a teleconverter works by spreading the image circle out to cover more area, right? It's not actually the same as making the lens zoom twice what it previously was, that's why it's darker. Right?

A 2x teleconverter doubles the size of the image circle, so a crop lens on a crop body would be effectively doubled.

A full frame lens on a crop body would be doubled, too, of course, but only the part that touches the sensor matters.

A crop lens on a full frame body, though… that would typically cover, what, 2/3 of the sensor/film? So if you used a 1.5x teleconverter, that would spread it approximately enough to cover the film plane without losing much, which would make a crop sensor 50mm give the same 75mm field of view on the full frame that it would have given without the teleconverter on a crop camera, right?

and why am I thinking about this stuff when I'm supposed to be coding? Work ethic fail.
12-10-2013, 11:15 AM   #11
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QuoteOriginally posted by narual Quote
and why am I thinking about this stuff when I'm supposed to be coding? Work ethic fail.
Because you have a subconscious need to lose your job and move to the West Coast with all the other coders.


Steve
12-10-2013, 11:38 AM   #12
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QuoteOriginally posted by stevebrot Quote
Because you have a subconscious need to lose your job and move to the West Coast with all the other coders.
Oh, you heard me complaining this morning, too? Ugh. I think it was 4 or 5 degrees (Fahrenheit, even -- much worse than Celsius) with a windchill of 17 below or some nonsense when I went out to breakfast this morning.

My current contract is based in a suburb of San Diego. I wouldn't mind working out of their office instead of from home right now. But then I probably couldn't afford all this fun camera stuff.
12-10-2013, 11:55 AM   #13
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QuoteOriginally posted by narual Quote
A crop lens on a full frame body, though… that would typically cover, what, 2/3 of the sensor/film? So if you used a 1.5x teleconverter, that would spread it approximately enough to cover the film plane without losing much, which would make a crop sensor 50mm give the same 75mm field of view on the full frame that it would have given without the teleconverter on a crop camera, right?

and why am I thinking about this stuff when I'm supposed to be coding? Work ethic fail.
That's right. Cropping with optics do the same thing as using a smaller sensor or cropping in PP.

So to get a lens with APS-C image circle to cover a FF image circle you will get the same FOV on both.
But most APS-C lenses has a larger than APS-C image circle, so it might be enough with something like 1.2x TC to get them to cover a FF image circle. (and quite a few APS-C lenses cover full FF image circle).
12-10-2013, 12:11 PM   #14
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QuoteOriginally posted by narual Quote
I think it was 4 or 5 degrees
Pretty cold, though to be fair, nightly lows here in the "Silicon Forest" have been in the low teens (F) this last week.
12-10-2013, 06:33 PM   #15
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QuoteOriginally posted by i83N Quote
Is it possible to create an adapter for apc lenses that will "boost" their coverage area to an ff lens level? If metabones booster can boost aperture why not boost an coverage?
They will never make that because there are full frame cameras that have an APS-C mode (36mp FF, 16mp APS-C) already and many APS-C zooms like the 10-24mm Tamron show a full frame with no vignetting from 13mm to 24mm.
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