Sigma 8mm Vs Sigma 4.5mm

[BETO74 0]

I was comparing the specs in these 2 lenses and I dont understand how both claim 180 degrees angle of view one being 8mm the other 4.5mm. The only explanation I can reach is one is wide horizontally and the 4.5 is all round tru wide angle lens. If anyone here can elaborate better it will be great.

I did saw a couple examples of the images taking from a full frame camera. the 8mm gives distortion expected from a wide angle and not vignette. The 4.5 alomost the same wide angle view witha 360 vignette around the image.



I copy and paste the following:

Sigma 88mm-F3.5EX

Filter size: drop in gel
F/Stop Range: 2.8-22
Minimum Focus Distance: 5.3"
Magnification: 1:6
Angle of View: 180
Groups: 9/13

Sigma 8mm-F3.5ex

Filter size: Rear Gel
F/Stop Range: 3.5-22
Minimum Focus Distance: 5.3"
Magnification: 1:6
Angle of View: 180
Groups: 6/11

http://web.mac.com/ac057a/iWeb/AC057A/H0M3.html

[shogo 0]

The sigma 8mm is for the full frame giving a circular image on a full frame sensor, and the sigma 4.5mm is for the cropped sensor giving a circular image on a cropped sensor. I think 8mm can be used on a cropped sensor, but 4 corners still gives black edges so you need to crop the image to get diagonal fisheye (as opposed to circular fisheye image.)

Edit. Samyang BMFIN is referring to is a diagonal fisheye for a cropped sensor equivalent to the sigma 10mm fisheye.

[BMFin 0]

The way I understand it is that Focal lenght is only one factor determining the field of view. Image projection is another one.

If every lens would produce a rectilinear image, then focal lenght would determine FOV of each lens. However different lenses produce different image projections and therefore FOV will differ at same focal lenghts for example.

Also the 8mm can see 180 degrees already. It is not a suprise that the 4,5mm cannot do more than this. You need a VERY complex optics, if you want the lens to be able to see behind it self.. (such lenses exist though, like the Nikon 6mm)

If you look at some of the 8mm fisheyes for example, they dont all produce the same kind of image. For example the new Samyang 8mm has a stereographic projection that differes from the Simga 8mm. The 4,5mm image projection is called circular fisheye.

Explained here:
http://www.versacorp.com/vlink/jcreview/sy8rv9jc.pdf

Also it is not vignetting you see with the 4,5mm. It is just the edges of the image circle. Pretty much every lens will vignette. Some lenses more, and some others less.
Vignetting explained here:
http://en.wikipedia.org/wiki/Vignetting

Quote

I did saw a couple examples of the images taking from a full frame camera. the 8mm gives distortion expected from a wide angle and not vignette. The 4.5 alomost the same wide angle view witha 360 vignette around the image.

I doubt you saw 8mm on a fullframe based on your description. Fullframe + 8mm looks like this: http://www.flickr.com/photos/poppy-photography/4265904738/

Im not sure if I actually answered your question since I admit Im a bit lost with this subject my self also..

[BETO74 0]

Thank you for simplying it for me!

here is another question:

whats the difference between the two lenses assuming you're using a full frame camera? both will give you 180 view and a circular fish eye look. is the F/Stop ray that much of a difference between the two one being 3.5-22 and the other 2.8-22

Another question

When using a cropped frame camera. will it be safe to say that a 4.5mm lens will be the equivalent of a 10mm (more or less) lens in a full frame camera?

http://web.mac.com/ac057a/iWeb/AC057A/H0M3.html

[BETO74 0]

http://photo.net/canon-eos-digital-camera-forum/00VqEu?unified_p=1

just answered my own question. thanks for the help guys.

http://web.mac.com/ac057a/iWeb/AC057A/H0M3.html

[champu 1]

Quote

I was comparing the specs in these 2 lenses and I dont understand how both claim 180 degrees angle of view one being 8mm the other 4.5mm. The only explanation I can reach is one is wide horizontally and the 4.5 is all round tru wide angle lens. If anyone here can elaborate better it will be great.

8 mm Sigma on an aps-c looks like the attached.

The lens is capturing a 180 deg field of view, it's just falling off the edges of the sensor. This will happen with almost all lenses you use on an aps-c camera (the 4.5 mm being the only exception I'm aware of.)

[sdctlc 0]

This thread got me looking and what about this?

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=350291013594&ssPageName=STRK:MEWAX:IT

YouTube had a vid that says was shot with a Nikon 5000 and this lens. Did not look too bad and even if it is not perfect the price is not bad and seams to be a really nice value for the money...

http://www.youtube.com/watch?v=ZvgHbhxOYY8

So for under $300 USD delivered on e-bay with mounts for Canon, Nikon and Pentax has anybody seen/tried it?

Scott C.

"He who Hesitates Shall Inherit the Earth!"

[BMFin 0]

yes. this is the lens I mentioned with the stereographic projection image.

Have seen rewieves, and most likely ordering one pretty soon. It doesnt have AF, which is not a catastrofy at this focal lenght though.

[TomD 0]

One of my friends jumped the Samyang 8mm for a short while, awesome lens, brilliant pictures.......

However, after maybe 30 seconds in freefall he'd sometimes get a steamed up circle right at the centre of the picture, nothing he tried would stop it. This was in Spain in the summer so nice and warm, not very humid, maybe the odd bit of cloud kicking around here and there, no idea why! He's now swapped it for the tokina 10-17mm which seems to do the trick perfectly and is slightly more versatile for using on the ground too.

[PhreeZone 15]

I had a Canon 14mm ASP that I jumped for a bit that had the same issue. I think part of it is that on a lot of lenses like this the glass is just so thick that it does not have the ability to adjust in temperature at the rate the air temp changes in free fall so the glass remains cooler and then fogs up until it warms up. I tried one jump where I kept the lens in my jumpsuit and put it on right before exit and it seemed to do better but in the end it was not worth the issues and complications for me so I sold it. Lazlo has the lens now and I hear he got some great photos out of it so I'm impressed he managed that.

Yesterday is history
And tomorrow is a mystery

Parachutemanuals.com

[BMFin 0]

Quote

I had a Canon 14mm ASP that I jumped for a bit

Canon 14mm f/2.8 ?

Wow, that is one expensive lens you had there. Did you have it on an APS-C body ?

[TomD 0]

Quote

the glass is just so thick that it does not have the ability to adjust in temperature at the rate the air temp changes in free fall so the glass remains cooler and then fogs up until it warms up

That sounds plausible! Shame because it was a really nice bit of kit AND good value!

[PhreeZone 15]

It was the Sigma 14 Asp, not the Canon L , it was in very used condition when I got it. I was jumping it on my XTi. I wish I had the $ for the 14L...

Yesterday is history
And tomorrow is a mystery

Parachutemanuals.com

[wildcard451 0]

Quote

It was the Sigma 14 Asp, not the Canon L , it was in very used condition when I got it. I was jumping it on my XTi. I wish I had the $ for the 14L...

I've got the Sigma 14mm asp, and so far on the ground I love it, but mine in in 9+/10 condition. Gonna take it up for a spin once I mount my d90 here next week.

[kai3fly 0]

Just my thoughts and understanding from photography forums.

the Sigma is the poorest glass quality from the list below.
Canon being the best.

Canon 10-22mm (wide angle)
Tokina 11-16mm (hard to find) (wide angle)
Tokina 10-17mm ( a popular choice now for tandems) (fisheye)
Sigma 15mm (old skool popular choice for tandems)

http://www.kenrockwell.com/tech/digital-wide-zooms/chart.htm

[dragon2 0]

1) don't listen too much to Ken Rockwell
2) this particular sigma the 15mm f/2.8 is a pretty good lens, and in darker surroundings (sunset jumps, in the plane) the f/2.8 comes in very very handy. It's no comparison to the tokina 12-24 really it's better , also I've no idea why a decent fixed f/2.8 lens would be "old skool" I think you mean the sigma 10-20 here, that would be it's place in the "quality" lineup yes. But a fixed lens? Whole 'nuther animal, as is the f/2.8 it gives you. You should compare this lens to the canon 15mm f/2.8 and the nikon 16mm f/2.8 fisheyes really, where of course it ends up third

ciel bleu,
Saskia

[wildcard451 0]

Quote

Just my thoughts and understanding from photography forums.

the Sigma is the poorest glass quality from the list below.
Canon being the best.

Canon 10-22mm (wide angle)
Tokina 11-16mm (hard to find) (wide angle)
Tokina 10-17mm ( a popular choice now for tandems) (fisheye)
Sigma 15mm (old skool popular choice for tandems)

http://www.kenrockwell.com/tech/digital-wide-zooms/chart.htm

Kai, it's not the Sigma 10-20 listed in that chart. It's the older 14mm/2.8 prime aspherical. It can soften up a little in the corners, but overall have found it to be wonderful on the ground so far.
I don't even know if it is being made anymore, as I had to find mine used on eBay. We'll see how it holds up in the air this summer.