new 55mm lens for my C33 makes for a dark image in the WLF

[ryan_wolstencroft]

I finally got a 55mm lens off ebay for my Mamiya C33. I havn't had a

roll developed yet so i can't say anything about the image quality.

Something i have noticed though is that the image in the WLF is much

darker than it was with my 105mm lens on the camera. My guess is that

because the 55mm lens is a f/4.5 lens and the 105mm is an f/3.5 lense,

they have probably set the aperture of the viewing lense on the 55mm

to 4.5 also. Is this right? I suppose I could put my 105mm back on

the camera and stop down the viewing lense to 4.5 (it's adjustable for

DOF preview) and see how it compares, but I'll need to wait until i

finish my current roll before i do that. thanks guys.

[gene m]

Wide angle lenses always seem darker because the light is spread over a larger surface. Therefore each area of your vewfinder receives a smaller percentage of light than it does with a longer length lens. The difference between a 3.5 and a 4.5 lens is minor.

[graham_patterson1]

There's a stop less light to begin with - the viewing and taking lens maximum apertures match. If the screen or mirror are dirty it could exaggerate the effect.

 

Why can't you swap the lenses mid-roll - is the internal baffle damaged?

[tarashnat]

Ryan,

 

A lens with a maximum f/stop of f/4.5 will have a dimmer image on the focusing screen

(of an SLR) than a lens with an f/stop of f/3.5. If you stop the two lenses to f/5.6 they will

have the same image brightness, hence you would use the same exposure length to

expose the image on the film for both lenses at f/5.6. When engaging the DOF preview on

the lenses to the same focal ratio (f/stop) the image brightness should be the about the

same.

 

Taras

[victorm.]

Not only is the 55mm lens one stop slower (that's one half the light coming through!), the depth of field is greater than the 80mm, making the out of focus and in focus areas more difficult to differentiate on the screen.

[jorn ake]

There is a different screen for the 55/65 lenses, and though I think the difference accomodates parallax for those lenses primarily, it might also be brighter. At least, you can still get a Beattie screen for this beast, which will improve your life immeasurably - I say this after jealously looking through a friend's 330 with a Beattie screen just the other day. http://www.intenscreen.com/products_medium-format_mamiya.htm

 

For more information on Mamiya TLRs than I can provide, check here:

 

http://www.btinternet.com/~g.a.patterson/mfaq/m_faq-contents.html

[jeffrey_abelson]

The difference between 3.5 and 4.5 is 2/3rds of a stop - the slower lens is going to be darker.

[braden_barclay]

Ryan, the standard screen on the C33 isn't as bright as the C330, or the C330s for that matter. That in combination with a wide-angle lens that is f4.5 is what makes it more difficult to focus with, especially in the corners. I installed a Maxwell screen in my C33 a couple years ago and the difference was incredible. It made it a lot faster to focus, and compose. It's a little bit more finnicky to use with the waist level finder because the screen is at its brightest when viewed right at the middle, ie. tilting your head off-axis will make the screen look darker. I use the prism with mine which although adds bulk, makes the brightness even across the screen, and of course reveses the image laterally. I have compared the Maxwell screen in my camera to my brother's stock C330s, and the Maxwell screen is noticably brighter. Just some food for thought.