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The 22 mm gap....

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janneman02

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K8.4/2.8
----- 5.6
14mm (1)
----- 1
15mm (3)
----- 1
16mm (1)
----- 1
17mm (1)
----- 1
18mm (1)
----- 2
20mm (4)
----- 4
24mm (4)
----- 4
28mm (12)
----- 2
30mm (1)
----- 1
31mm (1)
----- 4
35mm (8)
----- 5
40mm (2)
----- 3
43mm (1)
----- 7
50mm (21)
----- 5
55mm (2)
----- 22
77mm (1)
----- 7
85mm (7)
----- 13
100mm (13)
----- 5
105mm (1)
----- 15
120mm (2)
----- 15
135 (7)
----- 15
150 (2)
----- 50
200 (8)
----- 100
300 (7)
----- 100
400 (5)
----- 100
500 (1)
----- 100
600 (3)
----- 400
1000 (2)
----- 200
1200 (1)
----- 800)
2000 (2)

Okay, so what is this????
Above a short list of all prime focal lengths used by Pentax
In brackets the number of models ever made.

After the "-----"another number, the more intelligent of you will have noticed that that is the differendce between the two focal lengths.

As you see, as the focal lengths get longer, the difference increases too in general.

But what has intrigued me for a while is the relative huge gap between the discontinued 55 and the 77/1.8....
Why does that gap exist????

I got wondering as during a recent shoot, I sometimes thought that 50 was too wide (don't have the 55) and 77 too tele....
(Looking at the exif data f the 28-70 I used the 60-65mm area quite a lot.)

--
janneman
http://www.pbase.com/jl2

 
Buy a good zoom. Sounds like the upcoming DA50-135/2.8 will be your baby. ;-)

I know of very few camera manufacturers that make a 65mm lens for 35mm film and DSLR format cameras. Even 70-77mm is relatively uncommon. More common are primes in the sequence

20, 24, 28, 35, 50, 85, 90, 100, 135, 200. Looking at the differentials: 4, 4, 7, 15, 35, 5, 10, 35, 65.

Perhaps you should re-cast your list with the notion of diagonal field of view differences, for both 35mm film and DSLR field of view. That might tell you something different about why various focal lengths seem common, and why you find yourself running a 60-65mm focal length.

90-100mm presents a very common field of view choice for 35mm cameras in portraiture. 1.5 x 60mm equals ...

Godfrey
 
Godfrey said:
Buy a good zoom. Sounds like the upcoming DA50-135/2.8 will be your
baby. ;-)
Click to expand...
I already have the FA*28-70/2.8, With tha lens in my posession I think the 16-50/2.8 will be higher on the wish list...
Godfrey said:
Perhaps you should re-cast your list with the notion of diagonal
field of view differences, for both 35mm film and DSLR field of
view. That might tell you something different about why various
focal lengths seem common, and why you find yourself running a
60-65mm focal length.
Click to expand...
Hmm could it be that simple??? How silly a question was that then :-)
Godfrey said:
90-100mm presents a very common field of view choice for 35mm
cameras in portraiture. 1.5 x 60mm equals ...

Godfrey
Click to expand...
--
janneman
http://www.pbase.com/jl2

 
Here is a guess: the gap is at the start of the telephoto range, and is not unique to Pentax. Many 35mm format lens systems have a far bigger gap, from about 50mm "normal" to 85mm "short portrait".

My guess is that since 50mm lenses can be very good even at low prices so that intermediate field of view in the range 55-77 (or 50-85) are got succesfully with cropping from 50mm, whereas once you go into the wide angle realm below 50mm, using a focal length that is significantly shorter (wider) than necessary and then cropping is less desirable, because every few millimeters shorter makes the lens design more difficult and more expensive. So prime users tend to match their wide angle focal lengths more closely to actual FOV needs, and avoid cropping.
 
janneman02 said:
(Looking at the exif data f the 28-70 I used the 60-65mm area quite a lot.)
Click to expand...
Ah, that is with a DSLR, whereas the gap is in lenses designed for 35mm format, so it translates to about 36-55mm for a Pentax DSLR. Does your EXIF reveal a lot in that focal length range?

(Actually, I used to take a lot at around 70mm in 35mm format, so I was often in the gap!)

P. S. There is a DA 70/2.4 coming soon, which will sort of split the current gap between 50 and 77.
 
You have too much time on your hands :D

I think you should look at the ratios, and disregard some of the "odd-one-out" lenses, (e.g. 17/30/105/120mms etc). BTW you dont know if those are the real focal lengths, zoom lenses are normally rounded to the nearest 5% or so (aparently)...

The ratios for lenses that were contempery is about 1.25 to 1.5, though you are right, there is a large relative gap between 50 and 77. Other manufacturers only have a 85, which makes for a whopping 1.7 ratio!

On the other hand I guess a ratio of ca. 1.5 in terms of focal length is about optimal
E.g.: 14, 21, 31, 50, 77, 135, 200, 300...
janneman02 said:
K8.4/2.8
----- 5.6
14mm (1)
----- 1
15mm (3)
----- 1
16mm (1)
----- 1
17mm (1)
----- 1
18mm (1)
----- 2
20mm (4)
----- 4
24mm (4)
----- 4
28mm (12)
----- 2
30mm (1)
----- 1
31mm (1)
----- 4
35mm (8)
----- 5
40mm (2)
----- 3
43mm (1)
----- 7
50mm (21)
----- 5
55mm (2)
----- 22
77mm (1)
----- 7
85mm (7)
----- 13
100mm (13)
----- 5
105mm (1)
----- 15
120mm (2)
----- 15
135 (7)
----- 15
150 (2)
----- 50
200 (8)
----- 100
300 (7)
----- 100
400 (5)
----- 100
500 (1)
----- 100
600 (3)
----- 400
1000 (2)
----- 200
1200 (1)
----- 800)
2000 (2)

Okay, so what is this????
Above a short list of all prime focal lengths used by Pentax
In brackets the number of models ever made.
After the "-----"another number, the more intelligent of you will
have noticed that that is the differendce between the two focal
lengths.
As you see, as the focal lengths get longer, the difference
increases too in general.
But what has intrigued me for a while is the relative huge gap
between the discontinued 55 and the 77/1.8....
Why does that gap exist????
I got wondering as during a recent shoot, I sometimes thought that
50 was too wide (don't have the 55) and 77 too tele....
(Looking at the exif data f the 28-70 I used the 60-65mm area quite
a lot.)

--
janneman
http://www.pbase.com/jl2

Click to expand...
 
Laurens said:
I think you should look at the ratios, and disregard some of the
Click to expand...
Laurens said:
The ratios for lenses that were contempery is about 1.25 to 1.5,
though you are right, there is a large relative gap between 50 and
77. Other manufacturers only have a 85, which makes for a
whopping 1.7 ratio!

On the other hand I guess a ratio of ca. 1.5 in terms of focal
length is about optimal
E.g.: 14, 21, 31, 50, 77, 135, 200, 300...
Click to expand...
Well put.

Here the 135 is the big jump at 1.75x.
1.59x from 85 though.

--
cheers!

Gunn

-- Get a big lens and get closer™.

http://www.dpreview.pentaxistDS.photoshare.co.nz

http://www.y3m.net/penwik/pmwiki.php/Main/PentaxLensWiki
 
You piqued my interest ...

With the DSLR, I tend to use 14, 28, 35, 50, 77, and 135 mm focal lengths.
With 35mm SLRs, I tended to use 21, 35-40, 50, 75 and 200mm focal lengths.

Here's how they map out when comparing diagonal field of view (in degrees):



The left column show bright yellow squares around the FLs I use now, and orange lettering on the FLs I used with 35mm SLRs. In the DSLR and 35m column, I've shaded the squares around my most used FoVs.

Interesting to compare it this way. The range is similar overall, the specific FoVs are set by available lens options.

Godfrey
 
Hmm

Little bit misleading to measure everything in mm and say that the difference between 20 and 30mm is the same as 60 - 70mm. Perhaps some one with lotsof time can re calibrate the list into field of view (degrees).

I guess what Im trying to say is that thinking from my own perspective, i'd never pay extra over my favrouite 50mm for another 5mm, whereas the difference between 20 and 25mm is substantial and therefore more justifiable in terms of cost.

I do love having the 50mm f/1.4 become a 75mm but can see that if you favoured around 90mm on 35mm size then you are a bit stuffed.
 
Godfrey said:
Buy a good zoom. Sounds like the upcoming DA50-135/2.8 will be your
baby. ;-)
Godfrey
Click to expand...
Thanks alot! All this talk and this comment got me thinking about what I keep running up against with my current set-up. Now I have another lens I must buy. I know that everyday I come home with new camera gear even if it is just a ring for my filters that I risk hearing about. I figure my wife is biting her tongue and keeping score. I can see it now when I slink in the door with another lens - whamo. Guess I better start saving for some diamonds.

--
What if the Hoky-Poky really was what it's all about?
 
Laurens said:
The ratios for lenses that were contempery is about 1.25 to 1.5,
though you are right, there is a large relative gap between 50 and
77. Other manufacturers only have a 85, which makes for a whopping
1.7 ratio!

On the other hand I guess a ratio of ca. 1.5 in terms of focal
length is about optimal
E.g.: 14, 21, 31, 50, 77, 135, 200, 300...
Click to expand...
I read some advice somewhere that said a good progression of primes is approx the f-stop sequence - which is a ratio of about 1.4.

Ed
 
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