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A superfast normal on the G1

Cine lenses and their coverage depend on the format they were intended for 8mm, super 8, 16, super 16, 35, super 35, and even larger.
A rough indication could be given by the film/sensor size in mm (data from Wikipedia):

4/3 : 13x17.3
M8 : 18x27
16 : 7.49x10.26
Super 16 : 7.41x12.52
35 : 18x24

The only lenses covering the whole μFT sensor according to these values would be cine lenses intended for 35mm. Other lenses, such as some Super 16, may have a larger coverage than theoretically needed.

The 9.8mm Kinoptik Tegea, a 35mm cine lens, is for instance quoted to have a 25mm Ø coverage. This is not enough to cover the full M8 sensor but should cover the 4/3 sensor. I can confirm this for the M8 and am looking forward to receiving the G1 (should arrive later today) to test it on that body.
 
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guidomo

Guest
Monza and Vivek,

The apparent FOV doesn't depend on the image circle
On the focal length and FOV, what Monza said. Don't let the crop factor confuse you. It will not change the focal length of a lens.
I admit , I am not getting it. I am still unsure as to the FOV of a cine lens of a given nominal (as printed on the lens) FL on the G1. Let's say you position your G1 with a distance of 1.00m from a wall (sensor-to-wall distance) and you shoot a tape measure fixed to that wall. With your 25mm lens, what horizontal length do you capture?

I presume if you guys are clear on the FOV you do not need to do the experiment but can actually calculate it.

Thanks for enlightening feedback.
 

Jack

Sr. Administrator
Staff member
Most still photographers are not concerned with precise FoV calcs, since what they see in the finder is pretty much what they'll get; we know that our normal lens delivers this look, and our short telephoto delivers that look... OTOH, video folks seem to rely more heavily on precise calcs -- and I am NOT a video guy --- however I'll contribute this:

The formula for ANGLE of view (W) is as follows, where y is the image vertical, horizontal or diagonal dimension (your choice depending on which angle you want to know) and f is the lens focal length:

W = (2 x Tan^-1 x y)/2f

FIELD of view is determined using a simpler law of similar triangles, though you can derive it using the some more trig on the above formula. Anyway, similar triangles approach is:

Object dimension/object distance = image dimension/focal length.

Note that these are only as precise as the focal length estimation, since lenses are only their stated length at infinity, and get longer as you focus closer... So if you want more precision in your calc, the basic lens formula for focal length is:

1/object distance + 1/image distance = 1/focal length.

Hope that helps ;)
 

monza

Active member
That brings back memories of my waves & optics class at the University of Texas way back in 1982. My professor is still teaching...

In any case, a given lens's focal length remains the same, whether the lens is attached to a 35mm camera, a 16mm movie camera, a G1, or a 6x7. That lens may or may not have a large enough image circle to cover these frames.

Using 35mm full-frame as the reference and the generally accepted crop factors, a 25mm lens when used on:

- 35mm full frame is 1x25mm = 25mm
- M8 is 1.33x25mm = 33mm
- Nikon DX is 1.5x25mm = 37mm
- 4/3 sensor = 2x25mm = 50mm
 
V

Vivek

Guest
Jack nailed it with a great explanation covering all the angles. :)
 

Jack

Sr. Administrator
Staff member
does stopping down help the vignetting?
Typically yes, especially with a conventional symmetrical, double-gauss or plasmat lens design. However, most retro-focus or tele designs are limited by free aperture and stopping down won't help much if at all.
 
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Vivek

Guest
Most likely this is a double gauss variant.

Here is the lens characteristic (blank wall is the target at ~0.8m) focus was at the center:

 
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psurfer

Guest
Hey Vivek, yeah, DOF control -in Spades- at 0.95
You could just about tell where that guy missed shaving...

re the b/w coverage illus shot sequence, I don't know if you shot that? but judging by your posted real-world® shots, it's coverage on m4/3 sure looks better/larger (unless in the turnarounds of resizing/posting/etc some of your full image area was lost).

Here's what I vaguely recall being told once about the Angenieux 0.95 versions: The first chrome barrel one was developed for c-mt, for all the 16mm cameras that were starting to sell in numbers in the US at the time (B&H, Kodak). Small size mattered for those fairly small 3-lens turrets. This thing is small but Solid, btw. Feels like a solid slug of nickel that could have been loaded into a howitzer in a pinch...

Later they improved adapted/remade it in Arri mt, w/part chrome and part black barrel, for the beefier Arri's (16S, 16M, probably the 16BL was intro'd by then, which was used more often on tripod), so increasing size (also) had the advantage of giving a camera operator or focus puller a larger ring to grab and read. -The orig version is set up more as a trad rf lens/ordnance.

Then, the all-black 3rd and Penultimate version (... just trying to keep up w/that evocative "Sybaritic" rendering description earlier ...) which you now sleep w/under the pillow, no doubt. Improved further coatings, and whatever other Parisian flavor they managed to charm it with.
I'm not sure about it being intended for S16 though, as that wasn't really catching on until some years later, just beginning at the end of the 70's.

Most all of the big-gun cine lensmakers' primes were consistently good to exc by the 60's-70's, esp for 35mm -remember what the end use of the glass was typically for (not 8x10 prints). Ang, Cooke, Schneider, Zeiss, oh my.

Anyway, yes, your nice shots got me revved up for what I've had sitting in a shoebox, but I did expect my Oldie O.95 would be something of a dog wide-open for stills; but still hoping for some "character" nevertheless. --Not to mention being able to "see something" half-way "clearly" in low light on this G1! -f/3.5 and up just don't cut it in that finder for me in what I call available light...
(So when is that Raynox c-adptr selling already? And when are the really cheapo versions going to make this a less risky experiment? C-mt should be about the easiest adptr to make.)

And for those thinking it's a cheap way in, I doubt that most 16 lenses -let alone in c-mt, will cover as generously as Vivek's magic 0.95, although some were known to cover more than 16.
 
V

Vivek

Guest
Peter, Thanks a bunch! I greatly appreciate the information you have provided.

I don't think it is a matter of size. The Som-Berthiot lens I mentioned could be housed in a very small sized lens casing. It does cover the whole of the 4/3rds sensor (albeit with similar -ve distortion). I am sure you will put your 0.95 lens to good use.

Again, your detailed information is much appreciated!:)
 
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psurfer

Guest
You're right, strike my comments about the bigger size- I was thinking more in terms of concerns for 35 cine lenses. As a matter of fact, looking at your lens' focus barrel I see it has about the same throw distance as the old one, ~quarter turn from inf to 5ft. (35 lenses benefit from long barrel turns for ease in controlling focus moves by assistants.)

If mine turns out to have half the crisp clarity of yours wide open, I sure could put it to good use.
 
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Vivek

Guest
Let me add these to address the bokeh question:

At ~1.5m (all wide open) and ISO200, 1/100s.



At ~0.5 (closest focus) and ISO100, 1/20s.



and at somewhere in between, ISO100, 1/3s (hand-held!).

 
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psurfer

Guest
That looks like it strikes a nice balance to me. Mine will probably bloom and soften wide open in comparison. Probably wait for a decently priced C-mt adptr to find out; I'll predict that to be w/in 3-4 weeks...
 
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Vivek

Guest
There are very very few lenses that will not make a sensor bloom when pointed to bright lights.

Yes, affordable adapters should be coming soon.
 
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dng88

Guest
There are very very few lenses that will not make a sensor bloom when pointed to bright lights.

Yes, affordable adapters should be coming soon.
From camera world not video/16mm world, I am confused.

Can I say I just get a c-mount adapter and a Angenieux 0.95/25 and it would be good to try? Or the c-mount lens actually has many different spec. and in fact Angenieux 0.95/25 is not c-mount even (M1/M2/... types), hence just get a c-mount adapter is not that useful?

Very confused but I quite the picture you took. Also, the 0.95 is very important. It would be much less those "video" feel in handling I guess, wouldn't it?
 
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Vivek

Guest
The type M1 Angenieux 25/0.95 was only in c-mount, I think. That would fit with a c-mount adapter.

I have only seen one type M2 sample (mine). That is in Arriflex mount.

If you find any of the type M2 in c-mount, it is quite likely that it is already fitted with a Arri to c-mount adapter. This adapter business or changing of the camera mount is quite common in the movie gear world, I understand.
 

phobus

Member
Speaking of cheap experiments, I got a C mount adapter from Taiwan, and the Carl Zeiss Jena Tevidon 25mm 1.4 from eBay and its working out quite well for about $100 total for both. :) I'd love to be able to get a 0.95 one day though!

all at f1.4







 
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