Yep, you're talkin' real crazy!
Think about it: if f/8 (or any other f-stop) was different from lens to lens, then you'd not get the same exposure for the same f-stop when you changed lenses.
The whole idea of f-stops is that is proportional to aperture size so the amount of light transmission is always the same for a given number.
Example: f/8 on a 90mm lens = 90 ÷ 8 = 11.25mm. f/8 on a 150mm lens = 150 ÷ 8 = 18.75mm. The longer lens has a larger aperture at f/8 than the shorter, which lets in more light, which compensates for the smaller field of view.
For a given aperture size for both lenses, your reasoning is correct. It's just that the f-numbers would then be different.
Example: A 9mm aperture on a 90mm lens = f/10 (90 ÷ 9 = 10). That same 9mm aperture on a 150mm lens = f/16.6 (150 ÷ 9 = 16.666...). The division works both ways.
Some things can affect transmission, like haze on lenses, reflections from lots of elements, etc., but that's a separate issue from the f-stop.
Best,
Doremus
I plan on shooting chromes down the road in addition to BW. Would that change anyone's opinions on which 90mm lens? (Note that I have all filters in 77mm. So I don't want to go above that filter size)
Flickr Home Page: https://www.flickr.com/photos/alanklein2000/albums
...color chromes and color negatives...
Flickr Home Page: https://www.flickr.com/photos/alanklein2000/albums
I'm currently only doing black and white ( 4x5 TMax 100 and 5x7 Delta 100) on LF and then scanning for digital post-processing and printing.
That hybrid process allows me a fair degree of digital correction in post-processing and I have a wide-format Epson 7900 printer that can do excellent BW prints if carefully calibrated. That affects my own approach.
Some of the best aspects of LF photography are that a wide range of options and approaches are open to everyone, that nearly any age, make and model lens can be adapted to a LF camera, and that DYI is feasible for virtually anyone with a modicum of experience. That makes LF quite flexible and allows everyone to find their own approach.
Chromes are certainly more susceptible to vignetting and more difficult to correct. I cannot comment about shooting LF chromes as I lack personal experience there.
That said, while some may take a different and possibly idiosyncratic view, IMHO sharpness and contrast are very important optical criteria, although certainly not the only ones, because higher sharpness and crisp contrast usually record the image more faithfully and thus provide more "information" and more accurate information, than lenses that are not as sharp nor exhibiting crisp contrast.
You'll of course find differing opinions - think 1930s Pictorialists vs. the f/64 revolution by Edward Weston, Ansel Adams, et al. It all depends upon what you want to do and whether you want to achieve a particular result and do so in-camera via a particular lens.
If you want a softer image, that's possible after the fact IF you start out with enough information in the original image capture, but you can't go the other way and try to extract more information from an image where the underlying information was never captured when the shutter was clicked.
Older lenses would likely be less suitable for chromes than more modern lenses from Nikon, Schneider, Rodenstock, and Fujinon, all of whose more recent products have excellent reputations.
Hi, Dan: Thanks for the information about the 1.5 stop vignetting - I forgot the formula. As I shoot only BW at this time on LF and then scan, post-process, and digitally print, I haven't been bothered by the vignetting due to my own style but I can certainly see how it would be a concern when shooting chromes as per the OP.
Hello, Bernice:
FWIW, although I have mentioned that modern Fujinon lenses have proven to be reliably good for me and relatively more affordable used, I am not a Fujinon evangelist as I also use multiple modern lenses from Schneider, Nikkor, and Rodenstock. That said, the Fujinons and Rodenstocks have, for me, been the most consistently good optically.
I certainly understand your thoughts about the look of a certain lens as I also shoot regularly with eight classic lenses, four Zeiss Protar VIIa, a Voightlander 115mm Ultragon, and three Dagor lenses, and keep an appropriate one in every one of my large format kits from 4x5 through the 11x14 outfit. Some of these are as good as the better modern lenses and some less so.
Wait now I'm further confused lol.
f/8 for any two different focal lengths is the same light input total. Isn't it kinda like slow, wide river or fast, narrow river?
A 3000000mm f/8 is picking up light from like .0005 degrees, so to get a balanced exposure it needs to pick up a HECK ton of light/degree.
A 30mm f/8 is picking up light from like a jillion degrees, so it's a much lower level of light/degree.
If you have a totally dark room with one lightbulb in it, metering a 'correct' exposure at f/8 will yield two different shutter speeds for two different focal lengths. Right?
The wider lens needs a longer shutter speed because it's viewing more darkness, so the lightbulb takes up a lower percentage of the exposure.
The tighter lens can have a faster shutter speed because it's just looking at a lightbulb.
This is all based on a metering system looking for an average of zone V.
I feel even crazier now but there's something in my mind that doesn't click.
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