[ptx] Getting EXIF data from coolpix 950 jpgs using hugin

[Glenn Barry]

Hi Habi,

I've got a few different figures here for you to ponder.

Carl Zeiss Vario Tessar "folded" (internal) 3X Optical, 6.7 – 21mm 
(38-114mm equivalent)

Is listed on the site you linked

 From the lens figures:

Now if you simply divide the equivalent focal lengths by the actual 
focal lengths I get 5.4285714285714285714285714285714 at the long end 
and 5.6716417910447761194029850746269 at the short end. So lets say 5.55 
which sits about the middle.

 From the CCD figures:
Now not knowing if the CCD size quoted is the longest dimension or the 
diagonal, 3.4 is correct if it's the longest dimension of the CCD size 
as quoted. BUUUUUUTTT, if they're quoting the diagonal then the diagonal 
of 35mm film is 43.266. So your crop factor becomes 4.081.

Hmmm...seems to be difficult getting the same numbers from the different 
approaches. My theory on it is that the quoted lens equivalents are 
probably the best.

The reason that I say this is because the actual CCD may be 10.6mm 
(longest or diagional dimension, doesn't matter which), but the 
perimeter of the CCD probably isn't used, it isn't on most cameras I 
know of.
So the "actual" size of the CCD that contains active pixels goes down 
and the number for the "effective" crop factor goes up. To get an 
equivalent CCD size that yeilds a crop factor the same as that 
calculated by the lens equivalents, the active part of the CCD needs to 
be 7.866mm.
So there's approx 1.5mm on the periphery of the CCD un-used. This seems 
to me to be a reasonable result.
This ain't scientific though I "assumed" (made an ASS-out-of-U-and-ME) a 
lot.

You will probably be shooting all of your shots at wide setting, so just 
using the 21mm equivalent as quoted from Steves-Digicams is probably a 
safe bet. If you're going to use the exif data then a crop factor is 
required.

Regards

Glenn



David Haberthür wrote:
> hey glenn,
> thanks for posting this to the [ptx]-list.
> as i'm rather new with hugin, and never bothered to get the correct  
> crop factor (and did get rather good panoramas...) i'd like to ask if  
> my calculation below is correct:
> 
> my camera has a 1/2.4" sensor (according to http://www.steves- 
> digicams.com/2004_reviews/t3.html ). in metrical units this results  in 
> a size of 10.6 mm.
> hence my crop factor would be something like 3.4, is that correct?
> 
> thanks for the help.
> 
> habi
> 
> 
> On 02.12.2005, at 04:49, Glenn Barry wrote:
> 
>> Crop factor is the size of the CCD x A number to give 24mm x 36mm.  
>> Everything is still calculated relative to 35mm camera lens focal  
>> lengths in relation to 35mm film dimensions which are 24mm x 36mm.
>>
>> Grab the CCD sensor size from your manual, determine what it needs  to 
>> be multiplied by to give 24mm x 36mm and you've got your crop  factor. 
>> You may not need this IF the exif tags are already giving  effective 
>> focal length equivalents relative to 35mm film  dimensions. I don't 
>> know much about exif tags so this last part may  be totally wrong, but 
>> you should at least be able to understand the  principles to know if I 
>> am.
>>
>> Glenn
>>
>> Kevin Hanser wrote:
>>
>>> Quoting Pablo d'Angelo <pablo.dangelo at web.de>:
>>>
>>>> Kevin Hanser schrieb:
>>>>
>>>>> Hello,
>>>>>
>>>>> I have just recently discovered and started using the following  
>>>>> tools to create
>>>>> panoramas:  autopano-sift, hugin, panotools (PTStitcher), and  
>>>>> enblend.
>>>>>
>>>>> I have an old Nikon Coolpix 950 camera, and I have been unable  to 
>>>>> automagically
>>>>> read the lens settings using the "load EXIF" feature of hugin.   
>>>>> When I click on
>>>>> an image in hugin and pick "load EXIF", it then brings up a box  
>>>>> asking me for
>>>>> the focal length.  I've been putting this in manually for now  and 
>>>>> it works
>>>>> good, but I'm curious as to why it isn't able to get the info  from 
>>>>> the EXIF
>>>>> info in the jpgs?
>>>>
>>>>
>>>>
>>>> Hugin also needs information about the pixel size, because  without it,
>>>> the focal length is meaningless.
>>>>
>>>> Some camera do not save both in the EXIF data. Can you email me a
>>>> example image privately?
>>>>
>>>> ciao
>>>>  Pablo
>>>>
>>> I think what I actually meant was the "crop factor".  I'm not  
>>> entirely sure how
>>> to determine this... I've been basing it on the F-stop and that  
>>> seems to work
>>> ok, but I'm not sure if that's correct or not.  I will send you an  
>>> image
>>> shortly...
>>> thx!
>>
>>
> 
>