PDA

View Full Version : Angle of view confusion



donkittle
4-Feb-2016, 14:18
Hey all,

I'm fairly new to large format and have a question around the angle of view of lenses. In the full frame 35mm world that I've been a part of for a long time, the angle of view for a lens is more or less correlated to the focal length with a 16mm lens being around 100 degrees or so (diagonally).

I just picked up a Nikon Nikkor SW 90mm F/4.5. I've not shot alot with it yet but I'm starting to prep for a big landscape photography trip in May.

I thought the 90mm would be similar to using a 30mm on Sony A7* cameras.

I was researching the new-to-me 90mm more and came across a site that indicated the lens has a 105mm diagonal angle of view. Does that mean I should see a scene that looks similar to my Sony with a 16mm lens on it?

Seems I'm not really getting something here... If anyone knows what's really going on here, I'd love some insights.
Thanks, Don

vinny
4-Feb-2016, 14:22
http://lensn2shutter.com/angleofviewchart.html

Sirius Glass
4-Feb-2016, 14:27
Welcome to Large Format Photography Forum

Alan Gales
4-Feb-2016, 14:47
It's hard to compare a lens on the A7 to a lens on a 4x5 because of the format difference. The A7 is more of a rectangle where 4x5 although also a rectangle is more square. To me a 90mm lens on a 4x5 would compare in look to a 25mm lens on your A7. Of course others disagree. I had a 25mm lens on my old Contax 35mm camera so I purchased a 75mm lens thinking that it would be similar. I found it too wide so I sold it and bought a 90mm which looked right to me.

You really have to try it out for yourself and see what you think. Welcome to the forum.

Tin Can
4-Feb-2016, 14:51
Draw it on graph paper and it makes better sense to visual thinkers.

This is a text forum.

Jac@stafford.net
4-Feb-2016, 15:02
4x5 and 8x10 feel wider to me because of the aspect ratio compared to my favorite 6x12cm and 6x9cm. You might find the same.

Dan Fromm
4-Feb-2016, 16:14
http://lensn2shutter.com/angleofviewchart.html

Vinny, shame on you for posting a link to another site.

Coupla days ago I sent the mods a polite complaint about one of themselves and ended up having an amicable discussion with Ralph Barker, who thought my complaint had to do with links to other sites, not a mod's invocation of a non-existent rule. In the course of the e-mail exchange Ralph told me that the mods were discussing whether to ban links to other sites -- like you, I post links to other sites -- and warned me that I probably wouldn't like their decision.

vinny
4-Feb-2016, 16:21
Vinny, shame on you for posting a link to another site.

Coupla days ago I sent the mods a polite complaint about one of themselves and ended up having an amicable discussion with Ralph Barker, who thought my complaint had to do with links to other sites, not a mod's invocation of a non-existent rule. In the course of the e-mail exchange Ralph told me that the mods were discussing whether to ban links to other sites -- like you, I post links to other sites -- and warned me that I probably wouldn't like their decision.
HAHAHAHAHAHAHHAHAHHAHAHHAHAHHA!
Large Format Moderators Forum
Yeah, I think more rules and more moderators are just what is needed to whip this place into shape.

donkittle
4-Feb-2016, 16:32
Thanks vinny!

Tin Can
4-Feb-2016, 16:41
Great...

Stop all links.

Let's go back to Morse code and Pony Express which are compatible with LF style.

I do see Oren's point though, all links die, just like all the image links die. Not allowing links to eBay and perhaps all sales sites can stop the self-serving seller, but also the soon junk dead link. I get it.

It is very frustrating doing research on this site with all the dead links.

Are we building a Data Base or a Tower of Babel?

Very curt sarcastic replies are also tough to interpret after their purpose has gone...

My latest pet peave is very wordy and inscrutable descriptions. We all could be better serving history with drawings, and images that are permanently attached here in the 750 Pixel LFPF manner.

Perhaps, I will try to take my own advice. :)

scheinfluger_77
4-Feb-2016, 16:43
Vinny, shame on you for posting a link to another site.

Coupla days ago I sent the mods a polite complaint about one of themselves and ended up having an amicable discussion with Ralph Barker, who thought my complaint had to do with links to other sites, not a mod's invocation of a non-existent rule. In the course of the e-mail exchange Ralph told me that the mods were discussing whether to ban links to other sites -- like you, I post links to other sites -- and warned me that I probably wouldn't like their decision.

How about we post the text of the URL without actually making the link live?

Tin Can
4-Feb-2016, 16:47
How about we post the text of the URL without actually making the link live?

The trouble with that is, some are very very long. Try it.

The polite way is to make a one word hot link.

Dan Fromm
4-Feb-2016, 16:58
[QUOTE=Randy Moe;1307125I do see Oren's point though, all links die, just like all the image links die. Not allowing links to eBay and perhaps all sales sites can stop the self-serving seller, but also the soon junk dead link. I get it.[/QUOTE]

I don't completely get Oren's point. It may be true that all links die but when we post a link we have the option of putting it away on archive.org, the closest thing the 'net has to a permanent repository. I sometimes do this. Turns out that many of my good ones are there already.

I don't completely get Oren's point. Not a happy thought, but this site will dry up and blow away before all of the links posted on it die.

I don't completely get Oren's point. Most of the links posted here are, like the one Vinny posted above, to sources of information. There's no easy way to post the information on this site. QT is, rightly or wrongly, worried about copyright issues. I learned this when I suggested that he mirror some of the documents I've written that are on the French LF site.

vinny
4-Feb-2016, 17:09
Now that we're thoroughly off topic: I belong to more forums than I can count such as machinists, boating, woodworking, fishing, hunting, photography, and others. None of them prohibit links and no one cries about it on a daily basis.

Corran
4-Feb-2016, 17:09
This thread isn't the place, but, when/if changes are made (or are in discussion) a topic in the Feedback forum would be prudent. I made the one regarding eBay but it seems like most people don't care. I get responses as well as mail/messages often when I make suggestions that I should just accept how things are because it's a "free website" but I think the website, and users, are best served by having an active dialogue and giving feedback as necessary.

Banning off-site links is ridiculous. If they include banning hotlinks to images, as many/most of us do, I will simply cease posting images. The forums tiny upload size and limitations are complete garbage.

Tin Can
4-Feb-2016, 17:10
Dan, I appreciate your efforts at data longevity.

I have chased and followed all the links I can find of yours. I read your lens info many times, it's extensive and important to me.

The live links are very informative, too bad I can't remember all the data I once could.

Then I forget how to find your initial links.

Doesn't matter much now for me, I'm just happy to wake up now and then.

Now what was I doing?

Tin Can
4-Feb-2016, 17:11
View of confusion----Angle

This topic fits.

Drew Wiley
4-Feb-2016, 17:18
View camera lenses are generally designed with spare area in the "image circle" to accommodate movements. In the case of this 90mm lens, a typical application
would be to allow a certain amount of front rise in architectural shots. The "angle of view" accounts for how much area is taken in by the lens at the published
specifications, which in this case might have been infinity at f/16. At smaller stops it would be even bigger. But this is a different concept from angle of perspective, which would be determined by the film size itself. With 4x5 film, you gain a somewhat wide-angle perspective. With 6x7 roll film it would be more
a "normal" 45 degree perspective similar to a 50mm lens on a 35mm camera because of the much smaller film size.

Drew Wiley
4-Feb-2016, 17:27
... Got interrupted... but I own one of these Nikon 90/4.5's and it's excellent, but distinctly wide-angle on 4x5. Since 35mm film and 4x5 have different proportions, it's impossible to make an exact correlation, but it might be analogous in perspective to a 35mm lens on 35mm film. Once you've started working
with the wonderful option of movements which view camera allow, you'll intuitively begin to appreciate the concept of usable image circle.

Alan Gales
4-Feb-2016, 18:29
... Got interrupted... but I own one of these Nikon 90/4.5's and it's excellent, but distinctly wide-angle on 4x5. Since 35mm film and 4x5 have different proportions, it's impossible to make an exact correlation, but it might be analogous in perspective to a 35mm lens on 35mm film.

Drew, this is just what I was talking about. I think my 121mm Schneider on 4x5 feels like a 35mm lens on a 35mm camera. It's funny how we all see differently about focal lengths. When I started large format I learned that I had to try lenses for myself to see what focal lengths I liked. I also learned that I like closer to normal focal lengths better than I did on 35mm. I'm not sure if it's the format or that I just changed.

Dan Fromm
4-Feb-2016, 18:50
Alan, I think there's something about formats. My most used focal length on 35 mm still is 105 mm, ~ 2.4 x normal. My most used focal length on 2x3 is around 100 mm, normal. And when I was shooting S8 my most used focal length was 6 mm and if I'd had shorter I'd have used it too.

ic-racer
4-Feb-2016, 19:13
I post links to threads on this forum from other forums all the time.

Alan Gales
4-Feb-2016, 21:35
Alan, I think there's something about formats. My most used focal length on 35 mm still is 105 mm, ~ 2.4 x normal. My most used focal length on 2x3 is around 100 mm, normal. And when I was shooting S8 my most used focal length was 6 mm and if I'd had shorter I'd have used it too.

Yeah Dan, I think you are right. I liked my 25mm and 100mm the best on my 35mm camera. When I bought a Bronica EC 6x6 I shot 40mm, 75mm and 150mm pretty equally. For 4x5 I like my 180mm and for 8x10 I like my 14" the best.

Doremus Scudder
5-Feb-2016, 05:26
Hey all, ... Seems I'm not really getting something here... If anyone knows what's really going on here, I'd love some insights.
Thanks, Don

Don;

I'll try to steer back on topic and see if I can answer the question succinctly yet thoroughly. :)

First, it is important to distinguish the angle of view from the angle of coverage. The former is the angle the lens sees, i.e., in front of the lens, the latter describes the angle between lens and film, i.e., how large an image circle is formed by the lens.

The angle of coverage then, has no relationship to whether a lens is "wide," "normal," or "long" for a particular film format. It is the angle of view that does this.

Normal focal length lenses are those in which the focal length is approximately equal to the diagonal of the film format. Therefore, 50mm for 35mm format, 80mm for 6x6cm and 150mm for 4x5 format are all considered "normal" because the angle they see about the same angle as our eyes; ~62. Wider than that looks progressively wider, narrower progressively longer. This is dependent on angle of view, but completely independent of angle of coverage.

With view-camera lenses, the amount of coverage is important; more coverage is needed than just what it takes to cover the format since camera movements need a lot of extra image circle. Therefore, it is the angle of coverage, often called "covering power" by Nikkor and others, that is the most important and the info that is given in the lens brochures. Schneider confuses things even more by calling the angle of coverage "angle of view" in their on-line info. Often the true angle of view isn't given at all in the data sheets. In any case, the 105 that you refer to for your lens is the "covering power," or the angle of coverage.

There are lenses of the same focal length for 4x5 format that have very different angles of coverage. For example, a 90mm Schneider Angulon has an angle of coverage of 81 and barely covers 4x5 (Schneider calls it "angle of view"...) while your Nikkor 90mm with 105 coverage covers with lots of room to spare allowing you to use rise, shift and front tilts and swings, which would not be possible with the Angulon without causing vignetting.

A common plasmat design 150mm lens on 4x5 throws an angle of coverage of about 70 and an image circle of 210mm; large enough to cover 5x7 and offer a lot of room for movements on 4x5. However, the same lens design with a 70 angle of coverage in 105mm only throws an image circle of 155mm; barely enough to cover 4x5 without movements. If you plan to use camera movements, this isn't the lens for you; you need something in a similar focal length but with a larger angle of coverage/image circle. Fortunately, there are other lens designs that do just that. They are called "wide-angle" in common parlance, which, for LF photographers, means that they have a wider angle of coverage (again, this has nothing to do with the wide-normal-long angle of view of the lens; it relates to coverage). This is confusing to those coming from smaller formats with fixed-lens cameras since "wide-angle" there refers to both coverage and view. We need to keep these two things separate in the LF world, however.

Anyway, we can get a 100mm lens (or in your case a 90mm) with a wider angle of coverage and be able to use movements. The angle of view, however, remains the same and identical photos taken with two lenses of the same focal length will be the same, regardless of the angle of coverage of the lens; the extra coverage just doesn't get used.

You should also know that most lenses come in design families with many focal lengths available in each family. In Nikkor parlance (since you have one) the "W"-series (for wide) indicates a lens-design family (plasmats) with about 70 of coverage (which is wider than simpler Tessar-type lenses, hence the "W"). Schneider calls theirs Symmars, Rodenstock calls theirs Sironar, Fuji is like Nikkor.

There is also a common family of "wide-angle" (of coverage) lenses. Nikkor and Fuji call theirs SW (Super Wide), Schneider Super Angulon, Rodenstock, Grandagon. There are many other design families with varying angles of coverage, but this gives you the general idea. Note that the families overlap. You can get a Nikkor W 135mm lens (slightly wider view than normal) with a 73 angle of coverage and an image circle of 200mm; enough for modest movements on 4x5. However, you can get a (larger, heavier and more expensive) Nikkor SW 120mm lens (close in focal length) with 105 of coverage and a whopping 312mm image circle; enough to cover 8x10 film.

How a lens focal length "feels" on a particular format is part science, part emotion. Angle of view relates directly to the "wide-normal-long" feel of the lens to a great extent. However, as formats get larger, negatives and prints usually get bigger and that feeling changes a bit (especially if the aspect ratio is different); normal angles of view seem a bit "wider" on a larger format for some reason. Still we can get a pretty good comparison by simply dividing focal length by film diagonal. A result of around 1 is "normal" (50mm/50mm=1 for 35mm; 150mm/160mm=0.94 for 4x5). Greater than 1 is "longer" (100mm/50mm=2 for 35mm, 300mm/160mm= 1.85 for 4x5); less than 1 is wider (28mm/50mm=0.56 for 35mm; 75mm/160=0.46 for 4x5). You can extrapolate further easily on your own.

Hope this has helped,

Doremus

Bruce Watson
5-Feb-2016, 08:41
I'm fairly new to large format and have a question around the angle of view of lenses. In the full frame 35mm world that I've been a part of for a long time, the angle of view for a lens is more or less correlated to the focal length...

Not more-or-less, but based directly on focal length. Angle of View (https://en.wikipedia.org/wiki/Angle_of_view) = alpha = 2 arctan(d/2f), where d is typically the length of the film diagonal and f is the focal length of the lens.

Don't confuse angle of view with angle of coverage. Angle of coverage is a lens design parameter. This distinction matters in a world where the film plane and the lens plane are independent as they are in most view cameras (this is what camera movements manipulate). In 35mm where the plane of the film and the plane of the lens are rigidly parallel, these terms tend to get used interchangeably, which confuses the heck out of newbies. At least, it confused the heck out of me.

cowanw
5-Feb-2016, 11:15
I started to write that lenses would be independent of what is behind them but everybody has a different view of angles, so I stopped.