Railroad Forums 

  • Why do I keep getting tricked by my telephoto lenses?

  • Discussion of photography and videography techniques, equipment and technology, and links to personal railroad-related photo galleries.
Discussion of photography and videography techniques, equipment and technology, and links to personal railroad-related photo galleries.

Moderators: nomis, keeper1616

 #186164  by Otto Vondrak
 
I am an amateur photographer. I've snuck my way into Railpace a few times and a couple of books, but that's about it.

I have been shooting slides for about five years with my trusty Pentax K-1000. I have three lenses- a fixed 50mm, a fixed 28mm, and a fixed 135mm. Let's say it's a bright sunny day--blue dome, Kodachrome sky, whatever you want to call it--and I'm trackside in the Northeast. I slap on the 50mm lens and head trackside. My camera's meter says f8 at a 250th. Oh, but I want to capture the S-curve down the line a bit, so I slap on the 135mm. Now my meter says I'm a full stop too dark at f8/250. I decide the wide shot is better- I slap on the 28mm, and now my camera says almost a stop and a half too much light at f8/250.

Needless to say, I've ruined a lot of shots by "compensating."

I rely on the meter in the Pentax to tell me what's what. The only time I deviate is when it's cloudy or overcast or twilight, more or less.

Should I invest in my own hand-held meter, and rely on that? In the meantime, should I only rely on the meter reading from the 50mm lens?

-otto-

 #186238  by MEC407
 
When you're using the wide angle lens, you're capturing more area (and more light). When you're using the telephoto lens, you're capturing less area (and less light). That's why you get different meter readings with different lenses.

 #186248  by railohio
 
MEC407 nailed it right on.

When I'm running with my manual focus cameras I usually do all the metering in my head. "Sunny 16" really does work after all these years. To be honest, after five years of Nikon matrix metering I've lost my edge and would have a hard time doing it center-weighted again. Keeping notes and referring to them is the best way to teach yourself how to compensate and how not to.

 #186285  by EdM
 
MEC407 wrote:When you're using the wide angle lens, you're capturing more area (and more light). When you're using the telephoto lens, you're capturing less area (and less light). That's why you get different meter readings with different lenses.
Yeh, but that should be washed out, that is why lens' have F stops. i.e. are specified by F stop instead of diameter... Note that a long focal length lens has a larger apature and a higher F stop, again, that is what F stops take care of.. I can give you an absolute positive; "damned if I know"... Could be sumpin to do with center weighted metering, poor metering or lack of it...my best guess... This should not be happening... Ed K2LCK..

 #186331  by Ken W2KB
 
EdM wrote:
MEC407 wrote:When you're using the wide angle lens, you're capturing more area (and more light). When you're using the telephoto lens, you're capturing less area (and less light). That's why you get different meter readings with different lenses.
Yeh, but that should be washed out, that is why lens' have F stops. i.e. are specified by F stop instead of diameter... Note that a long focal length lens has a larger apature and a higher F stop, again, that is what F stops take care of.. I can give you an absolute positive; "damned if I know"... Could be sumpin to do with center weighted metering, poor metering or lack of it...my best guess... This should not be happening... Ed K2LCK..
I concur with the "more light," but more specifically, more bright sky with the wide angle, less with the telephoto. I particularly notice this with my Pentax istD digital since I get instant feedback. I have three lenses and note the same as Otto.

For photos of the ground looking more or less down from my airplane, I don't notice any difference since the entire frame is below the horizon. But for a shallow angle, with sky, the exposure changes.

---Ken W2KB

 #186341  by EdM
 
yeh,OK. Ken.... but a spot or center weighted meter should wash this out.. I disagree with his more light premis...

But more sky is different...

Sure with a wide angle lens you are going to see more sky and if you don't compensate, you are going to have dark people... This is not the fault of the lens, it is what the lens sees. Back in the old film days, this was reason for using a really slow speed film (like panatomic X or K25), greater dynamic range.

Geez, a photog hasta realize that the scene is not going to be uniformly lit, and know enuff not blame it on the focal length of the lens or lite meter....I use the spot or center weighted center of my frame to grab the lite meter (exposure) and hold it , then re-compose the frame and take the shot. The same is done with the focus but sometimes that is more difficult.. The main DISadvantage of a lite meter is the inability to read in most lite meters, the light level where the exposure is most critical. One must realize that to photograph a person inside a room from outside, one hasta expose for the person.. And if you are gonna photograph a train, you had better not take a meter reading offa the sky...unless you like black trains... You hafta accept a burned in (over exposed) sky to get the loco. And taking other than a spot (TTL) lite meter is going to give you BOTH an overexposed sky and an underexposed loco.. The worst of both worlds.. Ya gotta be at least semi-smart...

So: use your telephoto lens to get the exposure from the train, THEN set your wide angle lens to that exposure and take the shot...

.. Ed
Last edited by EdM on Mon Nov 21, 2005 6:42 am, edited 1 time in total.

 #186575  by Otto Vondrak
 
Spot or center-weighted meter? What do those terms mean?

So it sounds like if it's an f8/250 day, and my 50mm agrees, I shouldn't fuss with the exposure even if I switch lenses. I've noticed that a "perfectly metered" 28mm shot is still a stop over exposed. Sounds like I need to pay more attention to my lenses, and possibly invest in a meter!

-otto-

 #186625  by railohio
 
A spot meter uses the central most area of the frame, usually less than five percent of the total area. My Nikon N80 has its spotmeter in one percent of the total frame. It's handy for targeting exposure for a specific area in the frame. They are found on most advanced amateur and professional cameras as well as in seperate handheld models.

A center-weighted meter evaluates the whole frame but has an emphasis on the central region, thus the name. My Nikon FE has a 60/40 split and the N80 has a 75/25 split. Every manufacturer has its own way of dividing it up. Every manual focus camera in the last thirty years with a built-in meter has a center-weighted pattern. Again, most SLRs have it as an option in addition to evaluative and sometimes spot metering.

 #186635  by EdM
 
actually, since the 28mm lens sees more sky the rest of the photo will be UNder exposed... (black loco,dark people)....sigh..
There is no such thing as an f8/250 day.
. The range of light in an outdoor scene can be +- 3 to 5 or even more stops, the photog must first know that and second know what to do about it. The simplest way is to just take a meter reading off the GROUND (anywhere) and accept a burned out sky. The sky can be "darkened" with polarizing filters for Color, or a yellow(K2) or red(A) filter for b/w.

I have been shooting pictures since 1949 and own both digital and film cameras, though that doesn't say I know how to use 'em... Canon 30d,d10,d20,630 ,T70, Bron 4x6, Graphic 2 1/4 x 3 1/4 & 4x5 (no silver mine though) ...I had a coupla Nikons in the seventies, but the MTBF sucked (I could not seem to keep 'em working).. the darkroom stuff I am about to donate to the local high school... who BTW is still teaching BW photography (and probably Z80/CPM).... sigh^2! Ed
Last edited by EdM on Mon Nov 21, 2005 6:44 am, edited 2 times in total.

 #186757  by EdM
 
I disagree with his more light premis..

the wide angle lens views a larger scene, but admits the same amount of light, that is what the f stop insures.

If the wider scene contains more sky or sumpin bright (like the sun) well I guess that is more light, but that is not the same thing. If the wide angle lens expands the scene to include the entrance to a coal mine, it will see less light..

It is essential that a photographer understand the difference...(Photography 101) Ed

 #187068  by EdM
 
"

I want good exposure in the shadows and hilites and I want all the help I can get , therefore I use a slow speed color film and preferred K2 and panatomic X when I used to use film.

..

Ed
Last edited by EdM on Mon Nov 21, 2005 6:46 am, edited 1 time in total.

 #187085  by metman499
 
Otto, I had the same problems when I got my K-1000. It was that I was reading too much/little sky with lenses other than 50mm. After a little practice I figured out that if I aimed a little lower and picked up more ballast for my metering it would work just fine.

 #187177  by Otto Vondrak
 
Well, I went back to one of my locations and I took the same shot with the three lenses I own, all at f8/250, and f5.6/500. We'll see what happens!

Now I only pretend to know about cameras... so here goes...

The 135 is marked "1:2.8 f=135mm"

The 28 is marked "1:2.8 28mm"

The 50 is marked "1:2 50mm"

What do all these mean to me?

-otto-

ps- I shot Ektachrome E100S for years with very good results. I also like the E100G. But I stick with Fujichrome Sensia and Astia. But let's save film for another thread.

 #187181  by EdM
 
the f stop is the ratio between the focal length of the lens and its diameter.. it insures that the same f stop admits the same amount of light in an evenly lit scene... focal lenth, the length from the center of the lens to the film... all f:2.8 lens will admit the same amount of light to the film, a lens (telephoto) will have to have a larger diameter to have the same f stop and admit the same amount of light..
Last edited by EdM on Mon Nov 21, 2005 6:48 am, edited 4 times in total.

 #187183  by Alcoman
 
You may also want to bracket your shots using different meter readings and then you will get an idea of what works the best with practice when you get the results back. For action shots, its better to shoot at F8 or higher at 125 or 250 in good light. You will do better in "freezing" the action and less blur. At 250, you will have a little more depth of field-which means more of the subject will be in sharp focus.
This of course while using ASA 64 or 100 film. The faster the film, the smaller the lens opening has to be which gives more range to shoot with in different light conditions.

I also use 2 K-1000's . One has a standard 50mm lens at 1.2 ( widest lens opening for low light). The other lens is a zoom (50-70 mm) which I don't like because the focusing is very difficult to set for the sharpest picture. It does not have a good focusing screen.
A fixed telephoto lens works better.