XH A1 Zoom Number vs 35mm Equivalent Focal Length

Michael Wisniewski · January 28th, 2008, 03:58 AM

FWIW worth, I spent the evening with a digital SLR mounted above the XH A1, comparing different focal lengths. Everything between 35mm and 135mm matched very closely with the EXIF data - including the FOV. So I'm inclined to use the numbers from the EXIF data to calculate the 35mm equivalent.

Chris Hurd · January 28th, 2008, 09:19 AM

Well I'm still at a loss as to why there's so much disparity between the EXIF data and the F.O.V. test... but...

*If* we accept the EXIF data as valid, then here's a *rough* 35mm equivalency scale for commonly used focal lengths (except I know I'm missing a few of the more common 35mm focal lengths -- what are they?):

Code:

Z00	 32.5mm
Z02	 34mm
Z06	 36mm
Z10	 38mm
Z12	 40mm
Z19	 45mm
Z25	 50mm
Z29	 55mm
Z34	 60mm	
Z40	 70mm
Z46	 80mm
Z50	 90mm
Z54	100mm
Z60	120mm
Z64	135mm
Z65	140mm
Z70	165mm
Z75	200mm
Z80	240mm
Z85	300mm	
Z90	380mm
Z91     400mm
Z95	500mm
Z99	650mm

Cal Bickford · February 1st, 2008, 03:28 PM

I've used Chris's method and a multiplication factor of 7.2222222 to determine some of the more common focal lengths as they relate to Z#s. Hope this is helpful to you all...

To get as uniform a reading as possible, I set the zoom speed to 1 and gently tapped the zoom button until the Z# changed thus taking the reading from the very start of the zoom value as opposed to midway through (that is, you can actually zoom through Z5 a little bit before it changes to Z6 etc.)

all the values are usually accurate within a couple of tenths of a milimeter though at the upper end of the range (180mm and 300mm) they are within 2mm.

32.5mm=z0
35mm=z5
40mm=z12
50mm=z24
65mm=z37
75mm=z43
85mm=z48
100mm=z54
135mm=z64
150mm=z67
180mm=z72
300mm=z85

Cal Bickford · February 1st, 2008, 06:39 PM

whoops! just noticed that my post is pretty much a repeat of your last one chris. Didn't mean to steal your thunder lol but I guess I over looked that last post. Anyways, seems like our numbers are pretty similar.

Chris Hurd · February 1st, 2008, 10:06 PM

It's all good Cal. Reassures me that we're coming up with the same numbers.

Nic MacDonald · August 27th, 2009, 08:12 AM

Chris, Cal, this is brilliant, thanks for working this out. I think in 35mm focal lengths and tend to be quite organised (read: pedantic) about what lens length is used for what shots so it's always irritated me not really knowing what focal length I was shooting at, even roughly. I'm printing a list of 35mm equivalents and sticking it to the back of my camcorder.

Nic

January 28th, 2008, 03:58 AM	#16
Michael Wisniewski Wrangler Join Date: Jul 2002 Location: Makati, Metro Manila Posts: 2,706 Images: 32	FWIW worth, I spent the evening with a digital SLR mounted above the XH A1, comparing different focal lengths. Everything between 35mm and 135mm matched very closely with the EXIF data - including the FOV. So I'm inclined to use the numbers from the EXIF data to calculate the 35mm equivalent. __________________ "Ultimately, the most extraordinary thing, in a frame, is a human being." - Martin Scorsese

January 28th, 2008, 09:19 AM	#17
Chris Hurd Obstreperous Rex Join Date: Jan 2001 Location: San Marcos, TX Posts: 27,368 Images: 513	Well I'm still at a loss as to why there's so much disparity between the EXIF data and the F.O.V. test... but... If we accept the EXIF data as valid, then here's a rough 35mm equivalency scale for commonly used focal lengths (except I know I'm missing a few of the more common 35mm focal lengths -- what are they?): Code: Z00 32.5mm Z02 34mm Z06 36mm Z10 38mm Z12 40mm Z19 45mm Z25 50mm Z29 55mm Z34 60mm Z40 70mm Z46 80mm Z50 90mm Z54 100mm Z60 120mm Z64 135mm Z65 140mm Z70 165mm Z75 200mm Z80 240mm Z85 300mm Z90 380mm Z91 400mm Z95 500mm Z99 650mm __________________ CH Search DV Info Net \| 20 years of DVi \| ...Tuesday is Soylent Green Day!

February 1st, 2008, 03:28 PM	#18
Cal Bickford Regular Crew Join Date: Jan 2007 Location: Austin, TX Posts: 157	common 35mm focal lengths I've used Chris's method and a multiplication factor of 7.2222222 to determine some of the more common focal lengths as they relate to Z#s. Hope this is helpful to you all... To get as uniform a reading as possible, I set the zoom speed to 1 and gently tapped the zoom button until the Z# changed thus taking the reading from the very start of the zoom value as opposed to midway through (that is, you can actually zoom through Z5 a little bit before it changes to Z6 etc.) all the values are usually accurate within a couple of tenths of a milimeter though at the upper end of the range (180mm and 300mm) they are within 2mm. 32.5mm=z0 35mm=z5 40mm=z12 50mm=z24 65mm=z37 75mm=z43 85mm=z48 100mm=z54 135mm=z64 150mm=z67 180mm=z72 300mm=z85

February 1st, 2008, 10:06 PM	#20
Chris Hurd Obstreperous Rex Join Date: Jan 2001 Location: San Marcos, TX Posts: 27,368 Images: 513	It's all good Cal. Reassures me that we're coming up with the same numbers. __________________ CH Search DV Info Net \| 20 years of DVi \| ...Tuesday is Soylent Green Day!

February 1st, 2008, 06:39 PM	#19
Cal Bickford Regular Crew Join Date: Jan 2007 Location: Austin, TX Posts: 157	whoops! just noticed that my post is pretty much a repeat of your last one chris. Didn't mean to steal your thunder lol but I guess I over looked that last post. Anyways, seems like our numbers are pretty similar.

August 27th, 2009, 08:12 AM	#21
Nic MacDonald New Boot Join Date: Dec 2006 Location: Essex, England Posts: 22	Chris, Cal, this is brilliant, thanks for working this out. I think in 35mm focal lengths and tend to be quite organised (read: pedantic) about what lens length is used for what shots so it's always irritated me not really knowing what focal length I was shooting at, even roughly. I'm printing a list of 35mm equivalents and sticking it to the back of my camcorder. Nic