Home

Please support mflenses.com if you need any graphic related work order it from us, click on above banner to order!

SearchSearch MemberlistMemberlist RegisterRegister ProfileProfile Log in to check your private messagesLog in to check your private messages Log inLog in

Do Pen F lenses keep their focal length on m4/3?
View previous topic :: View next topic  


PostPosted: Fri May 11, 2012 7:18 pm    Post subject: Do Pen F lenses keep their focal length on m4/3? Reply with quote

now that i have m4/3 camera i can use Olympus Pen F lenses, so i am interested to know if those lenses keep their native focal length on 2x crop sensor, with Pen F being half frame format system?


PostPosted: Fri May 11, 2012 7:26 pm    Post subject: Reply with quote

Focal length does not change, what changes between formats is the angle of view...

Or to answer your question, a 50mm is always a 50mm, independently from the format it was originally developed for: a medium format 50mm lens will give you the same angle of view on m4/3 as a "normal" 50mm developed for the 35mm format. Which is half the angle of view you get on 35mm full frame.

A practical example: a 100mm lens on 6x9 has an horizontal angle of view of 45 degrees, on full frame 35mm the same 100mm lens gives you an angle of view of 20 degrees (20.41). To get 45 degrees on 35mm full frame, you have to use a 43mm lens.


PostPosted: Fri May 11, 2012 7:37 pm    Post subject: Reply with quote

ludoo wrote:
Focal length does not change, what changes between formats is the angle of view...

Or to answer your question, a 50mm is always a 50mm, independently from the format it was originally developed for: a medium format 50mm lens will give you the same angle of view on m4/3 as a "normal" 50mm developed for the 35mm format. Which is half the angle of view you get on 35mm full frame.

A practical example: a 100mm lens on 6x9 has an horizontal angle of view of 45 degrees, on full frame 35mm the same 100mm lens gives you an angle of view of 20 degrees (20.41). To get 45 degrees on 35mm full frame, you have to use a 43mm lens.


you misunderstood me, i know what you wrote about,after all i'm using manual lenses on 4/3 for 3 years now, but film Pen F system was half the 35mm frame, so the lenses for it must have been made to accomodate that. that being said, i believe, that if i use them on m4/3 angle of view stays the same.


PostPosted: Fri May 11, 2012 7:39 pm    Post subject: Reply with quote

The 'normal' PEN FT lens is 38mm - the fov on a m4/3 2x crop factor would give fov equivalent of 76mm in 35mm... No I didn't say that too clearly. The 2x crop factor applies for all lenses, to get the '35mm equivalent'.

The 'normal' 24mm lens for 110 is more like a m4/3 'normal'


pen FT lenses by Nesster, on Flickr


PostPosted: Fri May 11, 2012 7:43 pm    Post subject: Reply with quote

Nesster wrote:
The 'normal' PEN FT lens is 38mm - the fov on a m4/3 2x crop factor would give fov equivalent of 76mm in 35mm... No I didn't say that too clearly. The 2x crop factor applies for all lenses, to get the '35mm equivalent'.

The 'normal' 24mm lens for 110 is more like a m4/3 'normal'


so it doesn't matter that the lenses for PEN covered only half of the regular 35mm frame? or did they cover full 35mm frame but PEN camera used only half of that coverage?


PostPosted: Fri May 11, 2012 7:49 pm    Post subject: Reply with quote

WolverineX wrote:
Nesster wrote:
The 'normal' PEN FT lens is 38mm - the fov on a m4/3 2x crop factor would give fov equivalent of 76mm in 35mm... No I didn't say that too clearly. The 2x crop factor applies for all lenses, to get the '35mm equivalent'.

The 'normal' 24mm lens for 110 is more like a m4/3 'normal'


so it doesn't matter that the lenses for PEN covered only half of the regular 35mm frame? or did they cover full 35mm frame but PEN camera used only half of that coverage?


No it doesn't matter, as an example take most point and shoot - the focal length is written in 35mm equivalent.


PostPosted: Fri May 11, 2012 9:00 pm    Post subject: Reply with quote

WolverineX wrote:
Nesster wrote:
The 'normal' PEN FT lens is 38mm - the fov on a m4/3 2x crop factor would give fov equivalent of 76mm in 35mm... No I didn't say that too clearly. The 2x crop factor applies for all lenses, to get the '35mm equivalent'.

The 'normal' 24mm lens for 110 is more like a m4/3 'normal'


so it doesn't matter that the lenses for PEN covered only half of the regular 35mm frame? or did they cover full 35mm frame but PEN camera used only half of that coverage?


Half frame meant that the camera used a 18×24 mm vertical (portrait) format, producing twice the pictures on a roll of 135 film as the regular 36×24 mm format.


PostPosted: Sun May 13, 2012 5:58 pm    Post subject: Reply with quote

In fact the physical dimensions of a APS-C sensor is quite close to half frame of 35mm film ( 18x24 / 24x36 )mm, yet the cropping factor is only 1.5x / 1.6x. So the half size does not translate into a cropping factor of 2, the cropping ratio is determined by dividing the diagonal length of film format ( 43.3 for 35mm ) with the diagonal length of digital sensor. Also the ratio of the area swould be the square of the cropping factor...

If the sensor is exactly half the size of a 35mm full frame, the cropping factor should be 1.414, square root of 2, the same as the each step of lens aperture ratio...


PostPosted: Thu May 17, 2012 12:19 am    Post subject: Reply with quote

But 4/3 and Micro-4/3 have a 13 x 17.3 mm sensor. Yes, the Pen F lenses cover APS-C, but I think the only APS-C cameras with a small enough flange-to-sensor distance to be used with them are the Sony NEX's and the Fuji XPro-1. They won't work on any APS-C SLR I can think of.

So the 38mm lens was a "normal" lens on an 18 x 24mm half-frame exposure. On the Micro-4/3 sensor it will be a short telephoto, about the equivalent of a 75mm on a 35mm camera.


PostPosted: Thu May 17, 2012 10:00 pm    Post subject: Reply with quote

m43 sensor is close to "quart frame" Laughing

But as an multi user of m43 cameras, let's stick to the 2x crop factor term Wink


PostPosted: Fri May 18, 2012 10:15 pm    Post subject: Reply with quote

18x24 :
The 38mm is a 55mm 35mm equivalent
The 70mm is a 100mm 35mm equivalent
The 100mm is a 143mm 35mm equivalent
So m4/3 : Can we say that the 38mm is a 112mm 35mm equivalent ?
And Nex : a 83mm 35mm equivalent ?