Still confused about Lens Categories

Dammit, why is it that I can program a VCR and calculate IR exposures

accurately, but I CANNOT figure out which lenses go with my cameras?

 

<p>I have an *ist DS, a ZX-5n, and an MX. According to <a href="http:

//kmp.bdimitrov.de/">KMP's Pentax Guide</a>, (which has sadly not been

updated for digital), that means that means I can use all the lenses,

and I want to buy lenses marked SMC-FA ? So what's an SMCP-FA? Is that

good for digital? What happens if I stick my old SMCx-XX's onto my

digital?

Amul, it can be real confusing, but it helps if you think in broad categories. The FA and F lenses are both auto-focus and auto-exposure lenses(they have an "A" setting on the aperture ring that lets you control the aperture from the body and then the lens will stop down just as you push the shutter release). The A lenses are also auto-exposure, but they are manual focus. The K lenses and manual focus and manual aperture (you manually set the ring to the desired aperture). The old screwmounts can also work, but they need an adaptor. SMC refers to the wonderful Pentax coating on the glass to cut down flare. Digital body or not has nothing to do with lens compatibility, it's basically whether the body is autofocus and/or autoexposure that matters. So, go ahead and use any of those previous lenses on your *ist DS - they work great, especially the A, F, and FA lenses (the older K lenses work fine, but they require you to push an extra button to meter - but see the many other threads on this issue).

The digital bodies work fully with all lenses from KA (SMC-A, Takumar-A) on. These lenses all have an A position on the Aperture ring, or lack an Aperture Ring (DA and FA-J lenses lack the aperture ring and are permanently set to 'A'). All these lenses must be set to A to work correctly

 

Older lenses (SMC, SMC-M, Takumar-M as well as any lens with an adaptor) will work three ways on a DSLR, provided that you set the Custom Function which allows Shutter Release with lens set to Other than A.

 

With these lenses, you can shoot wide-open in Aperture Priority (Setting the camera to P, TV or any Program modes will default to Av), but the camera will not stop the lens down. If using a lens with an adaptor (M42, 645 or 67 lenses) the lens will stop down as you adjust the aperture ring, so you will get full aperture priority.

 

The next two options only work in M mode. You can adjust the aperture then press the AE-L Button (Green Button on the *istD) and the camera will stop down, meter and then set the appropriate Shutter Speed, or you can use the DoF preview to stop down and you will get a metering readout, which you can then adjust.

Adam,

 

<p>Thanks for that explanation, but I am familiar with how to operate in those modes.

(Although the subtle difference between auto-Av and manual-Av was new to me). My

question, though, is about the specific differences between types of lenses.

 

<p>For instance, this thread has already explained that:

<ul><li>FA, F = auto-focus, auto-aperture with option to switch to manual aperture

adjustment.

</li><li>A = auto-aperture, manual focus (which apparently = KA)

</li><li>K = manual focus, manual aperture

</li><li>DA, FA-J = fully auto, no option for manual

</li><li>screwmounts are completely manual

</li><li>SMC, I already knew, although I am still wondering what SMCP is.

</li></ul>

 

<p>To put it another way, I'm still trying to understand how to look at a webpage on, say,

B&H, and figure out what options the lens offers. To put it yet another way, I am trying to

figure out which lenses will be compatible with all three body types (the fully manual MX,

the full-auto ZX-5N, and the DSLR). Clearly, DA and FA-J lenses should be avoided in this

situation. The designations given by Pentax seem different than the ones used when

talking about them (eg, FA versus KA). But still there are questions: What's the difference

between F, FA, and FA-J? What do these letters STAND for? The Pentax sight does not

seem to offer any insight, or if it does, I cannot find it.

 

<p>I've been told that the DA lenses are "specifically designed" for the smaller DSLR

sensor plate. Is there some image quality issue that will arise from using pre-digital lenses

on DSLRs?

Keep it up Amul, we're all learning!

Amul asked: "But still there are questions: What's the difference between F, FA, and FA-J?

What do these letters STAND for? The Pentax sight does not seem to offer any insight, or if

it does, I cannot find it.

 

"I've been told that the DA lenses are "specifically designed" for the smaller DSLR sensor

plate. Is there some image quality issue that will arise from using pre-digital lenses on

DSLRs?"

 

Here is a short description of the various Pentax K-mount lens families:

 

- The first generation of K-mount manual focus lenses (pre-M type) didn't really have an

official identifying letter but are usually referred to as "K" lenses.

 

 

- "M" lenses are a later more compact manual focus design than "K" lenses; They were

designed to complement the Pentax M series bodies

 

- "A" lenses are a still later manual focus design offering optional aperture control by the

body and the

first with electrical contacts to transmit information from the lens to the body.

 

- "F" lenses are Pentax's first generation of autofocus lenses. They offer optional

aperture control by the body as well.

 

- "FA" lenses are the second generation of autofocus lenses; in addition to providing

autofocus and optional aperture control by the body they transmit additional information

to the camera body such as the maximum aperture of that specific lens for optimum MTF.

 

- "FA-J" lenses are low-cost third generation autofocus consumer zooms without an

aperture ring; the aperture is only controllable by the body, usually in autoexposure mode.

Not all Pentax bodies have the necessary controls to allow the user to control the aperture.

 

- "D-FA" lenses are the fourth generation of full frame autofocus lenses; they are

supposedly optimized to work well with both digital and 35mm film bodies. Unlike the

FA-J lenses the D-FA lenses have an aperture ring like the FA lenses, so the aperture can

be controlled either using the ring or from the body.

 

- "D" lenses are the first generation of Pentax lenses designed to cover the smaller

18x24mm digital

APS image format only. Because of this they can be made smaller and lighter than lenses

designed to cover the larger 35mm format, but they will usually vignette the image (yield

dark corners) if used on a 35mm SLR because the image circle they project is too small to

cover the full frame 24x26mm image. They do not have an aperture ring so aperture can

only be contolled by the body. All Pentax digital bodies offer this control.

 

I hope that this summary answers your questions. If you would like to know more, I

recommend that you go to Bojidar Dimitrov's Pentax K-Mount Page at <http://

kmp.bdimitrov.de/> for a full description of all Pentax K-mount bodies and lenses.

 

Regards, Jim