a. Determine the standard focal length of the camera. ie the focal length at which the scene through the viewfinder collates in size with that of the eye and take a photograph at that point.
b. From the same point take two photographs to demonstrate the different scenes obtained by adjusting the focal length of the lens to each extreme.
I used my 18-55mm lens for the exercise but was nonplussed immediately to find that I was unable to achieve part a. because even at a focal length of 55mm the objects in the viewfinder were still slightly smaller than my actual vision.
The photos for part b. are below. I stupidly forgot to note the camera settings so that's another lesson learned. The most I can say is that it was in manual mode.
This is the view with a focal length of 18mm
This is the view with a focal length of 55mm
The final part of the exercise consisted of printing all three photographs onto A4 paper, returning to the scene and ascertaining the required distance from the eye at which to hold the print so that it most closely resembled the actual size of the scene.
Reflection on Exercise 1. Focal length and angle of view.
Physically carrying out this exercise was simple and the visual differences resulting from the different focal lengths were self explanatory. But to say I have struggled with understanding the related theory is an understatement. With regard to lenses, sensors and finding the standard focal length of my own camera the workbook assumes a certain level of knowledge, stating that digital cameras are commonly of the ‘Four Thirds system (4/3), with proportions of 4:3 instead of the full-frame 3:2, and a smaller size, so that a standard focal length is a little less than 25mm.’ and ‘…when 35mm was the norm …with 50mm being accepted as ‘standard’. All well and good but what on earth are they talking about? Four Thirds of what? 4:3 and 3:2 as a ratio of what? All that I understood at this point was that in traditional 35mm full frame cameras the standard focal length was accepted as 50mm.
My peers raced ahead, blithely referring to crop factors and sensor percentages which are terms that I’d never even heard of. I referred to a variety of literature including my camera handbook, my ‘For Dummies’ reference book (see reading tab) and a huge array of on-line articles only to get increasingly confused. At this point I should have posted the question on the forum but I was concerned and embarrassed that I really didn’t understand the basics of the first preliminary exercise.
No doubt I could get by with just knowing that different focal lengths affect the camera’s angle of view, the apparent size and distance of objects in the scene and the depth of field but I like to understand the ‘whys’. It reminds me of school days when an irate maths teacher shouted at me for asking ‘why does a+b=c?’ The answer was ‘because it does’ but that wasn’t good enough for me then and it’s not now. Finally I found http://digital-photography-school.com/crop-factor-explained and things became clearer.
It seems that if you put a standard lens on most digital cameras the frame area is less than it would be on a traditional full-frame 35mm film camera. The reduction varies depending on the size of the sensor but the outcome is the same as if you took a picture on a 35mm camera and cropped it. Basically a smaller area is framed and there are implications on the depth of field which is explained in faIrly simple terms here ; http://www.the-digital-picture.com/Canon-Lenses/Field-of-view-crop-factor.aspx
My camera handbook tells me that my camera has a crop factor of 1.6. Therefore in order to ascertain an equivalent measure to a full-frame camera I must multiply the lens size by a factor of 1.6. This is illustrated in the table below taken fromhttp://digital-photography-school.com/crop-factor-explained .
This explains why, when carrying out exercise 1 with an 18-55mm lens, even at the maximum focal length of 55mm the scene through the lens was actually smaller than that which I could see by eye from the same distance. If, as stated in the workbook, 50mm is the standard focal length of a 35mm full frame camera, this would equate to an 80mm lens on my camera with its crop factor of 1.6. i.e. In order to frame the subject the same as for a 35mm camera (set at a focal length of 50mm) I would need to have a lens set at 80mm. There was no mention of such a focal length in the workbook so I was sure I’d got it wrong.
I followed the guide in the workbook and calculated the diagonal measurement of the sensor which came out as 35.3mm. When corrected by multiplying this figure by the crop factor (35.5 x 1.6) I found that the adjusted figure of 56.48mm was indeed in the realms of ‘standard focal length’ but remained confused as to why there was such a disparity. In desperation I resorted to posting the question on the forum.
Tutors and fellow students were extremely helpful in clarifying the issue and it seems that I wasn’t too far off the mark. They were also very reassuring that my question was valid. It transpires that the exercise will work on a 35mm full-frame camera but not on digital cameras with a crop factor where the standard focal lengths and sensor sizes are so variable. Now it all makes sense!
Consequently having felt well out of my depth, I now I feel that I have learned a great deal from this exercise, although I’ve realised that if I spend so long on each exercise I’ll need several years to complete the first module never mind the degree! I’ve also learned to ask for help a bit sooner. So overall not a bad outcome for the first preliminary exercise although this photography lark is rather taxing. Time for a G&T while I gird my loins for Exercise 2.
b. From the same point take two photographs to demonstrate the different scenes obtained by adjusting the focal length of the lens to each extreme.
I used my 18-55mm lens for the exercise but was nonplussed immediately to find that I was unable to achieve part a. because even at a focal length of 55mm the objects in the viewfinder were still slightly smaller than my actual vision.
The photos for part b. are below. I stupidly forgot to note the camera settings so that's another lesson learned. The most I can say is that it was in manual mode.
This is the view with a focal length of 18mm
This is the view with a focal length of 55mm
The final part of the exercise consisted of printing all three photographs onto A4 paper, returning to the scene and ascertaining the required distance from the eye at which to hold the print so that it most closely resembled the actual size of the scene.
Reflection on Exercise 1. Focal length and angle of view.
Physically carrying out this exercise was simple and the visual differences resulting from the different focal lengths were self explanatory. But to say I have struggled with understanding the related theory is an understatement. With regard to lenses, sensors and finding the standard focal length of my own camera the workbook assumes a certain level of knowledge, stating that digital cameras are commonly of the ‘Four Thirds system (4/3), with proportions of 4:3 instead of the full-frame 3:2, and a smaller size, so that a standard focal length is a little less than 25mm.’ and ‘…when 35mm was the norm …with 50mm being accepted as ‘standard’. All well and good but what on earth are they talking about? Four Thirds of what? 4:3 and 3:2 as a ratio of what? All that I understood at this point was that in traditional 35mm full frame cameras the standard focal length was accepted as 50mm.
My peers raced ahead, blithely referring to crop factors and sensor percentages which are terms that I’d never even heard of. I referred to a variety of literature including my camera handbook, my ‘For Dummies’ reference book (see reading tab) and a huge array of on-line articles only to get increasingly confused. At this point I should have posted the question on the forum but I was concerned and embarrassed that I really didn’t understand the basics of the first preliminary exercise.
No doubt I could get by with just knowing that different focal lengths affect the camera’s angle of view, the apparent size and distance of objects in the scene and the depth of field but I like to understand the ‘whys’. It reminds me of school days when an irate maths teacher shouted at me for asking ‘why does a+b=c?’ The answer was ‘because it does’ but that wasn’t good enough for me then and it’s not now. Finally I found http://digital-photography-school.com/crop-factor-explained and things became clearer.
It seems that if you put a standard lens on most digital cameras the frame area is less than it would be on a traditional full-frame 35mm film camera. The reduction varies depending on the size of the sensor but the outcome is the same as if you took a picture on a 35mm camera and cropped it. Basically a smaller area is framed and there are implications on the depth of field which is explained in faIrly simple terms here ; http://www.the-digital-picture.com/Canon-Lenses/Field-of-view-crop-factor.aspx
My camera handbook tells me that my camera has a crop factor of 1.6. Therefore in order to ascertain an equivalent measure to a full-frame camera I must multiply the lens size by a factor of 1.6. This is illustrated in the table below taken fromhttp://digital-photography-school.com/crop-factor-explained .
Equivalent lens size for different crop factors
|
||||
Full frame
|
Crop factor 1.3x
|
Crop factor 1.5x
|
Crop factor 1.6x
|
Crop factor 2.0x
|
10mm
|
13mm
|
15mm
|
16mm
|
20mm
|
17mm
|
22.1mm
|
25.5mm
|
27.2mm
|
34mm
|
28mm
|
36.4mm
|
42mm
|
44.8mm
|
56mm
|
35mm
|
45.5mm
|
52.5mm
|
56mm
|
70mm
|
50mm
|
65mm
|
75mm
|
80mm
|
100mm
|
105mm
|
136.5mm
|
157.5mm
|
168mm
|
210mm
|
135mm
|
175.5mm
|
202.5mm
|
216mm
|
270mm
|
200mm
|
260mm
|
300mm
|
320mm
|
400mm
|
400mm
|
520mm
|
600mm
|
640mm
|
800mm
|
600mm
|
780mm
|
900mm
|
960mm
|
1200mm
|
This explains why, when carrying out exercise 1 with an 18-55mm lens, even at the maximum focal length of 55mm the scene through the lens was actually smaller than that which I could see by eye from the same distance. If, as stated in the workbook, 50mm is the standard focal length of a 35mm full frame camera, this would equate to an 80mm lens on my camera with its crop factor of 1.6. i.e. In order to frame the subject the same as for a 35mm camera (set at a focal length of 50mm) I would need to have a lens set at 80mm. There was no mention of such a focal length in the workbook so I was sure I’d got it wrong.
I followed the guide in the workbook and calculated the diagonal measurement of the sensor which came out as 35.3mm. When corrected by multiplying this figure by the crop factor (35.5 x 1.6) I found that the adjusted figure of 56.48mm was indeed in the realms of ‘standard focal length’ but remained confused as to why there was such a disparity. In desperation I resorted to posting the question on the forum.
Tutors and fellow students were extremely helpful in clarifying the issue and it seems that I wasn’t too far off the mark. They were also very reassuring that my question was valid. It transpires that the exercise will work on a 35mm full-frame camera but not on digital cameras with a crop factor where the standard focal lengths and sensor sizes are so variable. Now it all makes sense!
Consequently having felt well out of my depth, I now I feel that I have learned a great deal from this exercise, although I’ve realised that if I spend so long on each exercise I’ll need several years to complete the first module never mind the degree! I’ve also learned to ask for help a bit sooner. So overall not a bad outcome for the first preliminary exercise although this photography lark is rather taxing. Time for a G&T while I gird my loins for Exercise 2.
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