Luminous Landscape Forum
Equipment & Techniques => Medium Format / Film / Digital Backs – and Large Sensor Photography => Topic started by: Streetwise on February 12, 2010, 10:19:28 am
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I have an Aptus 65 (33x44 sensor) and have been trying to figure out what my Digitar 55 and 90 lenses are equivalent to in 4x5 terms. (I'm using the back on a Sinar P2). If 4x5 film has an equivalent "sensor" of 102mm x 127mm, would that mean that the Aptus has a crop factor of about 2.89x ?
The other thing I'm trying to figure out is the equivalent length on a Cambo Wide camera. I had heard that there's a .79x factor between the 24XL and that of a standard 35mm lens (24XL is similar to 19mm lens on 35mm FF). Does anyone know that to be true?
Thanks much.
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I have an Aptus 65 (33x44 sensor) and have been trying to figure out what my Digitar 55 and 90 lenses are equivalent to in 4x5 terms. (I'm using the back on a Sinar P2). If 4x5 film has an equivalent "sensor" of 102mm x 127mm, would that mean that the Aptus has a crop factor of about 2.89x ?
The other thing I'm trying to figure out is the equivalent length on a Cambo Wide camera. I had heard that there's a .79x factor between the 24XL and that of a standard 35mm lens (24XL is similar to 19mm lens on 35mm FF). Does anyone know that to be true?
Thanks much.
Focal Length Equivalent Calculator (http://www.captureintegration.com/2009/02/03/focal-length-equivalent-calculator/)
Thew Aptus 65 and P30+ are, for all intents and purposes, the same physical size, so just use the column for the P30+.
Reminds me to upload the version I have where we've added the S2, P40+ and Leaf lineup.
Doug Peterson ()
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Hi. Alpa has a great Photographical Calculations document which has most known formats and lens' listed. I refer back to it often. It can be found on the Alpa downloads page. http://www.alpa.ch/en/press/downloads.html (http://www.alpa.ch/en/press/downloads.html)
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I have an Aptus 65 (33x44 sensor) and have been trying to figure out what my Digitar 55 and 90 lenses are equivalent to in 4x5 terms. (I'm using the back on a Sinar P2). If 4x5 film has an equivalent "sensor" of 102mm x 127mm, would that mean that the Aptus has a crop factor of about 2.89x ?
The other thing I'm trying to figure out is the equivalent length on a Cambo Wide camera. I had heard that there's a .79x factor between the 24XL and that of a standard 35mm lens (24XL is similar to 19mm lens on 35mm FF). Does anyone know that to be true?
Thanks much.
Hi,
Actual - exact - conversion is actually simpler;
4x5 measures 118mm x 98mm
Aptus 65 sensor 44mm x 33mm
Thus,
Image circle of 4x5 = sqrt (118x118 + 98x98) = 153.4mm
Image circle of Aptus 65 = sqrt (44x44 + 33x33) = 55mm
A 4x5 150mm lens on Aptus 65 thus equals = 150mm x 55/153.4 = 53.7mm
BUT, above is based on image circle only.
More correct is to consider that the 4x5 format has proportions 5:4 or 1.25, while Aptus 65 has proportions 44/33 or 1.33.
How?
Simply look at what is the focal length in horizontal and vertical directions! For same example as above we have for a 150mm lens on 4x5...
Horizontal on Aptus 65 : 150 x 44/118 = 56mm
Vertical on Aptus 65 : 150 x 33/98 = 51mm
While if we compare the 150mm from 4x5 to the equivalent on 135;
135 format is 36x24mm, thus image circle is sqrt(36x36 + 24x24) = 43.3mm
per Image circle = 150 x 43.3 x 153.4 = 42.3mm
per Horizontal = 150 x 36/118 = 45.7mm
per vertical = 150 x 24/98 = 36.7mm
Regards
Anders