Go Back   Steve's Digicams Forums > Digital SLR and Interchangeable Lens Cameras > Pentax / Samsung dSLR, K Mount Mirrorless

Reply
 
Thread Tools Search this Thread
Old Jun 28, 2006, 8:21 AM   #11
TDN
Senior Member
 
TDN's Avatar
 
Join Date: Jun 2006
Posts: 1,288
Default

Oh. But doesnt that still mean you get 1.5 times more zoom range?

The only disadvantage of that crop factor I could think of is for pancake or fisheye lenses, where you're trying to get an as wide as possible field of view...or does it affect the quality aswell?
TDN is offline   Reply With Quote
Old Jun 28, 2006, 9:16 AM   #12
Member
 
Join Date: Apr 2006
Posts: 64
Default

The only thing Pentax did with this new lens system is turn me away from using there new lenses. I am still active with my 35mm, and one of the reasons I bought the DL is so that the camera's lenses would work together. I guess this can only be accomplished without using the new Pentax digital lenses. :sad:

But my new tamron is comming today
TravisG5 is offline   Reply With Quote
Old Jun 28, 2006, 9:31 AM   #13
Administrator
 
Join Date: Jun 2003
Location: Savannah, GA (USA)
Posts: 22,378
Default

TDN wrote:
Quote:
Idd.
Quite frankly, I just don't get why they want to make the image circle on lenses smaller.
Because the lenses can be smaller and lighter for the same focal range and brightness.

Quote:
I mean, doesn't using a 35mm lens on a digital mean you will automatically get better results with regards to vignetting, pincushion, etc, because you have a larger image circle?
That's going to depend on the lens.

Quote:
And what about that 1.5 magnification of the focal length, that's a great plus. Why would they want to get rid of that?
You don't "get rid of that". A "made for digital lens" with a smaller image circlebehaves the same way from an angle of view perspective as one designed for 35mm cameras when used on a DSLR with a smaller sensor.

You still need to multiply the focal length of the lens by 1.5x to see how the angle of view compares to a lens on a 35mm camera.

As for it being a "great plus", that depends on what you're shooting. ;-) If you like a wider lens, a smaller sensor can be a drawback.

Lenses are marked by their actual focal length. Focal Length doesn't change based on what type of camera a lens is mounted on.

Angle of view is what changes based on sensor or film size, and a "made for digital" lens will behave the same way (same apparent magnification) as one that was made for 35mm cameras when used on a DSLR with a smaller sensor.

If you use a smaller sensor or film size, the angle of view will be narrower (more apparent magnification) for any given focal length.

If you use a larger sensor or film size, the angle of view will be wider (less apparent magnification) for any given focal length.

The only reason to even have a so called crop factor or focal length multiplier is so that users familiar with using lenses on 35mm cameras have a better understanding of how angle of view compares.

If 35mm cameras were not so popular, there would be no need to use them at all.


JimC is offline   Reply With Quote
Old Jun 28, 2006, 9:31 AM   #14
Senior Member
 
ennacac's Avatar
 
Join Date: Mar 2005
Posts: 4,198
Default

TDN wrote:
Quote:
Oh. But doesnt that still mean you get 1.5 times more zoom range?

The only disadvantage of that crop factor I could think of is for pancake or fisheye lenses, where you're trying to get an as wide as possible field of view...or does it affect the quality aswell?
There is no more zoom range than there would be with 35mm film and you are correct the real problem with the crop factor is on the wide angle side, where your field of view is less than it would be with film or a full size sensor.

Tom
ennacac is offline   Reply With Quote
Old Jun 28, 2006, 1:19 PM   #15
Junior Member
 
Join Date: Jun 2006
Posts: 4
Default

Hi all! I'm new here. "New" means that I've been visiting this forum for quite a while but never spoke a word, coz I'm not even a DSLR user, yet. I just want to get involved now.

My understanding of the question is that "made for digital lens" can be used on film SLR, but since they intend to produce images on sensors that are smaller than the film, if they are used on film SLR, they will produce smaller images, leaving the corners on the film black.

Aperture ring is a problem that I'm not very sure of. Does a lens without aperture ring means the aperture is controled by the camera body instead of the lens itself? If that's the case,lens without aperture ring can only be used with cameras that can control aperture onthe body. Is this a line between digital and film?Does any film SLRcan do that? Correct me if I'm wrong, I heard that Pentax Jseries lens have no aperturering, are they for digital only? If not, then there must be film SLRs that can work with lens without aperture rings.

For thecompatibility philosophy, I think most people consider filmto digital as "upgrade" though it's not necessary getting better (just like MS windows, everytime they introduce a bunch of junk, they call it an upgrade). So Pentax's down-compatiblity means newer cameras (digital) can use older lens (for film) but not vice versa.
NotLeo2nd is offline   Reply With Quote
Old Jun 28, 2006, 3:56 PM   #16
TDN
Senior Member
 
TDN's Avatar
 
Join Date: Jun 2006
Posts: 1,288
Default

NotLeo2nd wrote:
Quote:
Aperture ring is a problem that I'm not very sure of. Does a lens without aperture ring means the aperture is controled by the camera body instead of the lens itself? If that's the case,lens without aperture ring can only be used with cameras that can control aperture onthe body. Is this a line between digital and film?Does any film SLRcan do that? Correct me if I'm wrong, I heard that Pentax Jseries lens have no aperturering, are they for digital only? If not, then there must be film SLRs that can work with lens without aperture rings.
Well, most Pentax lenses (those with the KA mount) have an "A" marked on the aperture ring. This refers to the automatic position. WHat that means is that the body can decide which aperture the lens uses. This way, the body does all the metering, calculates the shutter speed, and matches it with an aperture. I don't know about analog bodies, but on the DSLR's you can control the aperture from inside the body manually too.

So basicly the DA series are lenses with "just" that "A" position.


(Someone more experienced please correct me if I'm wrong )

TDN
TDN is offline   Reply With Quote
Old Jun 28, 2006, 3:59 PM   #17
TDN
Senior Member
 
TDN's Avatar
 
Join Date: Jun 2006
Posts: 1,288
Default

ennacac wrote:
Quote:
There is no more zoom range than there would be with 35mm film and you are correct the real problem with the crop factor is on the wide angle side, where your field of view is less than it would be with film or a full size sensor.
Huh? I'm kinda lost here, so what's all that talk about "an 80-200mm becomes a 120-300mm" then?

TDN

TDN is offline   Reply With Quote
Old Jun 28, 2006, 4:09 PM   #18
Administrator
 
Join Date: Jun 2003
Location: Savannah, GA (USA)
Posts: 22,378
Default

TDN wrote:
Quote:
Huh? I'm kinda lost here, so what's all that talk about "an 80-200mm becomes a 120-300mm" then?
I think the key word was "range" (probably meaning the difference between widest and longest zoom settings). ;-)

If you use an 80-200mm lens on a Pentax DSLR, you will have the approximately same angle of view as you would using a 120-300mm lens a 35mm camera.
JimC is offline   Reply With Quote
Old Jun 28, 2006, 4:11 PM   #19
Senior Member
 
Join Date: Jun 2006
Posts: 400
Default

TDN, yeah, I was confused by this magical lengthening of my lenses too. As I understand it the digital sensors are smaller in area than the rectangle of film that is exposed to the image.



So, if I use my K1000 with a 100mm lens and take a picture of my back yard it will include everything from the rubbish tin at the gate to the dog kennel, if I used my 150mm lens it would only include as far as the kids bike lying in the driveway.

Likewise, if I put that same 100mm lens on my digital I would still miss out on the dog kennel.

The lens is not longer, the picture is smaller.



Isnt marketing grand?




John Hill is offline   Reply With Quote
Old Jun 28, 2006, 5:00 PM   #20
Senior Member
 
ennacac's Avatar
 
Join Date: Mar 2005
Posts: 4,198
Default

My kit lens does not work on my MZ-S, so I expect it will not work on any Pentax film camera.

Tom
ennacac is offline   Reply With Quote
 
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



All times are GMT -5. The time now is 4:10 AM.