'Digital' lenses

[4walls]

Ok, I am looking at the Sigma 18-125/3.5-5.6 DC Aspherical IF Zoom Lens for
Canon. One review I read stated:
The Sigma is designed for Digital SLR. So its image circle falls neatly inside
my Canon DRebel's APS sized sensor. Therefore an 18mm is really an 18mm.

Is this true? Does a 'digital' lens take into account the magnification factor of
digital SLRs? If so, how do they know which camera I am going to use the lens
on? If I use a 1D MkII, then the mag factor isn't the same as on a 300D.

Comments?

[PacAce]

Yes, it's true that an 18mm lens is an 18mm lens but it's also true that my 70-200 IS L is also a 70-200 lens. in other words, although the lens is an 18mm lens, you'lll still get the ***** <<censored :lol: >> effect that all lens exhibit with a 1.6x sensor. :)

[4walls]

Ya, I thought so. I was surprised to read this "18 is really an 18" comment.

[Kenski]

Ok, I am looking at the Sigma 18-125/3.5-5.6 DC Aspherical IF Zoom Lens for
Canon. One review I read stated:


Is this true? Does a 'digital' lens take into account the magnification factor of
digital SLRs? If so, how do they know which camera I am going to use the lens
on? If I use a 1D MkII, then the mag factor isn't the same as on a 300D.

Comments?


You have to be careful who is calling it DIGITAL... Tamron calls it DIGITAL but there 28-75 doesn't really mean 28mm-75mm on the 20D.... There digital lens scheme has something to do with that it is better for DSLR's.... Now, with the Sigmas I read an intresting article that if you would use this lens on a film camera you would get HORRIBLE vignetting... The lens was designed around the size of a CCD, now is focal length set up that way too??? I hope so!!!

[pcasciola]

The lens was designed around the size of a CCD, now is focal length set up that way too??? I hope so!!! We still have to do the math to get the "effective" focal length. I'm ok with this because it's confusing enough without having to worry about which lenses have accounted for x-factor and which have not.

The term digital is virtually meaningless now, though. The letters we need to be concerned with for smaller sensored cameras like the 20D/10D/drebel are:

EF-S (Canon), DC (Sigma), Di-II for Tamron

At this time these are the only lenses that are designed for the smaller sensor. It it also my understanding that the DC and Di-II lenses will fit a standard EF mount and are not EF-S mount, but will produce severe vignetting on full frame cameras.

[edsarkiss]

as far as computing an "effective" focal length -- this is a misnomer.

i think a better term would be "35mm equivalent" focal length.

as stated earlier, an 18mm lens is an 18mm lens. there is no two ways about this.

what really matters is angle of view on the desired capture media. a 24mm lens on a full-frame 35mm camera will capture roughly 90 degrees diagonally. on a DRebel, the same lens will capture about 60 degrees, due to the smaller sensor area.

[Kenski]

as far as computing an "effective" focal length -- this is a misnomer.

i think a better term would be "35mm equivalent" focal length.

as stated earlier, an 18mm lens is an 18mm lens. there is no two ways about this.

what really matters is angle of view on the desired capture media. a 24mm lens on a full-frame 35mm camera will capture roughly 90 degrees diagonally. on a DRebel, the same lens will capture about 60 degrees, due to the smaller sensor area.


Its not angle of view, it is actual CROP. If I take a 70-200 and slap it on a flim camera and snap a picture at 200mm and then slap it on my DSLR, the picture will looked CROPPED aka ZOOMED in... yes, the field of view will look like it has changed because it has because it has zoomed in slightly.

[edsarkiss]

it's either one -- if you crop an image, you limit the feld of view. it is either one. it doesn't matter if a lens projects a 1 foot diameter image at the focal plane -- the size [a.k.a "crop"] of the sensor/film/whatever determines the field of view represented in that image.

[Kenski]

***ouch.... double post edit***

[pcasciola]

as far as computing an "effective" focal length -- this is a misnomer.
Who cares? I said effective focal length, not actual. That is the purpose of the word effective, isn't it?

ef·fec·tive·ly http://cache.lexico.com/dictionary/graphics/AHD4/JPG/pron.jpg (https://secure.reference.com/premium/login.html?rd=2&u=http%3A%2F%2Fdictionary.reference.com%2Fsearch%3 Fq%3Deffectively) ( P ) Pronunciation Key (http://dictionary.reference.com/help/ahd4/pronkey.html) (http://cache.lexico.com/dictionary/graphics/AHD4/GIF/ibreve.gif-fhttp://cache.lexico.com/dictionary/graphics/AHD4/GIF/ebreve.gifkhttp://cache.lexico.com/dictionary/graphics/AHD4/GIF/prime.gifthttp://cache.lexico.com/dictionary/graphics/AHD4/GIF/ibreve.gifv-lhttp://cache.lexico.com/dictionary/graphics/AHD4/GIF/emacr.gif)
adv.

In an effective way.
For all practical purposes; in effect
I don't care that an 18mm is just an 18mm. All I care about is when I take a picture with an 18mm lens with my 20D, I will get "effectively" what an 8MP full frame camera would get with a 28mm lens, period. This way, when the 1D Mk II photographer tells me 400mm is just perfect for football, I know with my 20D a 300mm will give me about the same "effective" Focal Length/FOV/Angle of View/Crop Factor/Magnfication Factor/X-Factor/Put-your-term-here-factor as his 400mm.

Damn, my New Years resolution was no more x-factor posts, and here it is January 6th and I've already crumbled.

[flyfishnj]

Damn, my New Years resolution was no more x-factor posts, and here it is January 6th and I've already crumbled.
I thought you new years resolution was to buy more white lenses

[pcasciola]

I thought you new years resolution was to buy more white lensesWell, yeah, that's a given. :D

Oh, and, ummm, they're not really white. In fact, I think we should always argue this fact as well, because calling them white is just plain wrong. ;)

[HJMinard]

Oh, and, ummm, they're not really white. In fact, I think we should always argue this fact as well, because calling them white is just plain wrong. ;)

How 'bout caucasian? :lol:

[flyfishnj]

Well, yeah, that's a given. :D

Oh, and, ummm, they're not really white. In fact, I think we should always argue this fact as well, because calling them white is just plain wrong. ;)
Taupe, Off white, beige, x color ... Whatever -

[flyfishnj]

How 'bout caucasian? :lol:

Missed that one

[CyberDyneSystems]

S till calm falls over the cool ocean waters.. a fog horn in the dsitance.. then the subtle yet nervy bass chords start...

Bah dum,........ bah dum,... da dum...

the pace increases,. as does the volume.. BAH DUM DA DUH DA DUH DA DUH...

"Swim Eddy Swim!!!!!!"

It's the -JAWS- of the CDP Forum.. the ~X-Factor~!

:lol:

[Kenski]

hahaha, my dad and I got into a huge argument over 4x5 and 8x10 cameras talking about lenses and comparing them to the DSLRS... he can the the focal conversions in his head for 35mm - 4x5 - 8x10 all day, but when it comes to the DSLRS, he goes nuts... :)

[r2d2]

WOW. We are one sad bunch.... :)

[Kenski]

wait till be bust out the D&D dice or the magic cards....

[Hellashot]

The only reason it's a 18-125mm is that 18mm turns into 28mm effective on a Drebel.

You might consider the Sigma 24-135 f2.8-4.5 I am very seriously considering it too. The 24 turns into 38 but you end up with slightly larger appetures for $40 more. I am hesitant to buy any "digital" 35mm lenses in case I want to buy a film camera because it'd be useless on it or if I got a digital camera with larger sensor or a full frame sensor.

I hope Canon is not going to camp on the sensor size of these 3 cameras they have going.