Olypus pen FT-depth of field and focal length

<p>Dear all,<br>

I was wandering if you can help me with a dilema..<br>

I recently fell in love with the olympus pen ft, a SLR so small with a design that seems way advanced for 1963.<br>

I have seen one for sale at a price that requires a certain amount of efort from my side and i was wondering about depth of field and focal lenght.<br>

I have noticed that the standard lens is a 38 f1.8 which seems extraordinary; but then i started to have some doubts about this figures .<br>

Judging by its size and the fact that is half frame is indeed a f 1.8 equivalent with a full 35 mm frame camera? Maybe i compare with digital but i know form there , the smallest the senzor the depth of field goes bigger. <br>

Also this 38 is equivalent to a 50? Is the focal lenght the same? At 38 mm do i have the same field of view as on a full 35 mm frame camera?</p>

<p>Best Regards<br>

\Cristian</p>

<p> </p>

<p>If fields of view are equal you have to multiply aperture by crop factor to get similar DOF; i.e. the half frame lens would equal a 50mm f2.4.<br>

Precise math isn't my field, but 38mm on half frame should be a smaller step from a 50mm than a 60mm macro.</p>

<p>Half-frame is about the same size as APS-C, so the normal "crop factor" of 1.4 to 1.5 would apply. So, yes the field of view is about the same as a 50mm lens on full-frame.<br>

You also get the "more depth of field" of APS-C.</p>

<p>If it is working and the price is right...buy it! The meters suck, and the viewfinder isn't the best in the world....but...that standard kit lens is terrific. I still have razor sharp 8x10 prints hanging on the wall and in my portfolios from shots I took with mine 50 years ago. The only thing to get used to really is that the image format is portrait instead of landscape.</p>

<p>FWIW, doing the geometry, 38mm in half frame would be equivalent to a 55mm in full frame.</p>

<p>And yes, it is a real 1.8 aperture, and luminosity on the frame would be the same as that of an 1.8 lens in full frame.</p>

<p>The aperture number is just the focal length of the lens divided by the diameter of the lens opening. The maximum lens opening should be about 38/1.8 = 21 mm.</p>

<p>Thank you for the answers! So basically i have a 55 mm with an f 2.8ish (regarding DOF). Since in most ocasion i use DOF creativly and i have a lot of 2.8 film cameras, doesn't sound like something i would like. Also the availability of the lenses is quite poor. I have seen a 1.4 exists, but it is really rare and expensive</p>

<p> </p>

<p>The "power" of a lens (or luminosity) is NOT affected by crop factor/frame size etc. A lens with a max. aperture of f/1.8 has the same light collecting power for all formats. The maximum opening of a lens is set by design and does not change when used for other purposes/formats etc. </p>

<blockquote>"The "power" of a lens (or luminosity) is NOT affected by crop factor/frame size etc. A lens with a max. aperture of f/1.8 has the same light collecting power for all formats.</blockquote><P>

 

So true. The number of photos falling on the film is the same per square mm no matter the format size. Otherwise you would need an adjustment on light meters to correct for format size.

<p>Aside from the math, I find the 38 f1.8 to be a remarkable lens and I like the results better than some of my full frame cameras. Very sharp and with good contrast and somehow I haven't seen the severe grain that I was expecting. Really great camera though the prices have stayed high on these. </p>

<blockquote>

<p>The "power" of a lens (or luminosity) is NOT affected by crop factor/frame size etc. A lens with a max. aperture of f/1.8 has the same light collecting power for all formats.</p>

</blockquote>

<p> <br>

This is true, but you have to figure out what is constant, and what isn't. If you enlarge to the same size, you multiply the effects of grain. For similar results, you should use a finer grain film. If you use a slower film, you will need either a slower shutter speed, or larger aperture. <br>

Someone above noted the effects of aperture change.<br>

<br>

The smaller image is enlarged more, but subject or camera motion is reduced with the shorter focal length lens. Seems to me that those cancel out. You should use the same motion stopping shutter speed as you would with full frame. </p>