sigma 105/2.8 on a MX?

[max_steinhardt]

I was wondering if anybody has used the Sigma 105 2.8 Macro on a Pentax MX (or other non-af camera). I was

looking at macro lenses in this range and this one seemed both well reviewed and affordable. The thing that bugs

me is that I can't really wrap my head around the whole auto/manual focusing scheme that sigma has going on.

When the switch on the side of the barrel is set to manual, does it matter what the focusing ring is set to? If

so, how hard is it to accidentally set the focusing ring?

 

answers to these questions, as well as any other advice you'd like to give (like don't eat the yellow snow, etc)

would be greatly appreciated.

[andrewg_ny]

<p>I think it should be fine, assuming that particular Sigma has an aperture ring (on some of the latest lenses, these have been tending to disappear). Without being particularly familiar with the Sigma you're referring to:</p>

<p>I'm not sure what you're getting at with accidentally setting focusing rings, etc. I would expect an AF/MF switch on the barrel to be used to disengage the manual focus ring from the autofocus drive shaft (which would be linked to a motor in an autofocus body). If you're using it on an MX, you'd probably just leave it on MF all the time. Even in 'AF' mode, it would probably work the same since the AF drive shaft isn't connected to anything.</p>

<p>Most pentax-mount AF lenses don't really *need* an on-lens switch for MF/AF because the bodies have that switch. Some third-party lenses have this switch in part because they need it for other mounts (like Canon EOS) that don't have these switches on the body. Another possible reason for a switch is to make it easier to switch from AF to MF but this is often done (again, on some lenses) not with a small toggle but by declutching the whole focus ring forward or backward. The other switch that sometimes appears on telephoto or macro lenses is a focus limiter that can be used to limit focusing range for improved autofocus performance. Such a limit would have no real use on manual focus. Anyway, again because Sigma designs for several mounts, sometimes vestigial features are marketed as advantages when in truth they mostly confuse.</p>

[max_steinhardt]

*grumbles* yeah, forgot about the whole aperture ring thing. Guess that's the end of that story.

[john_h.1]

<p><em>When the switch on the side of the barrel is set to manual, does it matter what the focusing ring is set to?</em></p>

<p>No.</p>

<p><em>If so, how hard is it to accidentally set the focusing ring?</em><br>

<em></em><br>

Even if the answer is yes and assuming "set" means 'move', no more than any other lens. You would just leave it on manual. The focusing ring moves when you move it just like any other.</p>

<p>I have that lens and it works great.</p>

<p> </p>

[shots worth sharing]

<p>It is a nice lens and <em>does</em> have the aperture ring.</p>

[max_steinhardt]

Thanks everybody for the help. Dave, after a bit more searching, i see that you are correct, it does have a aperture ring =).<br><br> John, My concern is not with the normal clockwise/counter-clockwise movements of the focusing ring, but rather with what sigma calls their Dual Focusing system. I saw complaints stating that switching this lens to manual is a two step process; you have to set the barrel switch to manual and "declutch" (thanks Andrew) the ring forward or backwards (in other words, it has both a barrel switch and a clutch that need to be in manual).<br><br> I have never used a lens with the clutch system, and if it truly is a two step process, I worry about the interaction of accidentally changing the clutch position to 'Auto' would somehow being an annoyance/impediment to manual focusing on an all manual camera. More specifically, I worry that setting the clutch on auto would cause the focusing ring to spin freely so as to not hurt the autofocus systems, regardless of what the switch on the barrel is set to.<br><br> I hope this is a little more clear, but i kinda doubt it is.

[david_barts2]

<p>I have a 6-year-old Sigma autofocus 50mm macro lens that I use on my MX all the time. It works just fine.</p>

<p>The one thing to be aware of is that the focus ring feels different on an AF lens, sort of looser. That's not a terribly big deal in my book. What <em>is</em> sometimes an issue is how there's less than 5mm of movement from the 5-foot mark on the focus ring to the infinity mark on my lens; it makes focusing at non-macro distances quite tricky. Don't know of the 100mm lens you're eyeing has the same feature, but it's worth mentioning.</p>

<p>Based on my experience with a classic, manual focus 100mm Pentax macro lens, MF macro lenses don't have the same extreme focus compression issues AF ones do.</p>

[andrewg_ny]

<p>Max, that "Dual Focusing System" is what I was referring to before. It's sort of slapping a marketing label on to a combination of features that are really only all there because the lens was designed for multiple mounts. I wouldn't be too discouraged, it probably works fine when not in use. David makes a good point though that if you're only using the lens for manual focus & film, you're paying a premium over a solid used manual-focus macro lens. For example, I imagine you can find an M100/4 Macro (1:2) in great shape for < $200 (I did).</p>

[michael_kuhne]

<p>The clutch system will not cause complications. If there is no AF motor to engage, it will not be working against anything, and the focus ring is freed up when in AF, so nothing is engaged. The markings and position for MF/AF are clear. It is something to be more mindful of when using a lens that does not free up its focus ring on a body with AF.</p>

[max_steinhardt]

awesome, that clears it up =). thank you very one.<br><br> Yeah, I know that I could get a cheaper manual focus lens, but the last time I looked at the used sections on B&H/Adorama/keh (yesterday), the sigma is the cheapest option from those sites, barring screw mount lenses. I was surprised when the SMC A100/4 Macro went for about $100 more than the sigma on KEH, and figured that the 1:1 and faster speed made the sigma lens a better buy. I was also thinking that since there isn't much for a discount for getting the lens used, it might be nice to actually buy a new lens for once. I actually have the SMC-M 50/4 Macro, and after using it, a farther working distance and higher magnification appeal to me. Also, should i ever decide to get an AF camera, at least I would have 1 AF lens for it, even if the AF on the sigma is supposed to be kinda sub par, as all my other glass is SMC-M.

[andrewg_ny]

<p>For what it's worth, AF on most macro lenses is considered 'sub-par', mostly due to the super-long focus path (optimized for precise manual focusing) which makes any hunting take a <em>loooong </em> time. To my knowledge, the Sigma is par for the course here.</p>

[shots worth sharing]

<p>Although I use my Sigma in MF mode for my macro-ish shooting (I'm not a true macro-ist), the AF option adds an element of versatility. But, yeah, if you're looking for a dedicated macro lens, I'm sure you can get equal IQ in a MF lens for substantially less. In fact, having learned a lot (and added to my kit) since I bought the Sigma, I think that's the route I'd take if I were looking for a macro lens now.</p>

[max_steinhardt]

I dunno if I'd call myself a true macro-ist either, because i take a ton of non-macro shots. The thing is that in my eyes the Macro, not the zoom, is the king of versatility. Just as a a zoom user is willing to make a few picture quality trade offs to get a wide range of focal lengths, I will to make a few quality trade offs for the ability to get a wide range of magnification. My SMC-M 50/4 Macro is the lens that is on my camera the most, for both macro and as the standard 50mm. I like the versatility of being able to take snapshots and super close-ups, even if the snapshots aren't as sharp as my 50/1.4M. However, I run across a lot of occasions that I find the 50/4 is either too slow, the 1:2 magnification just isn't cutting it, or the >1 foot focal distance for 1:2 is just a little too close.<br><br>The second most used lens I own is the 135/3.5M. I love the focal length, but the roughly 5ft min focusing distance bugs me, and I'd kill for an extra 1-3 feet a lot of the time. Adding this to the issues i had with the 50/4, a longer macro lens seems to be a real winner. The sigma speaks to me because it is of a decently long focal length for both macro and non-macro, it's faster than my 50/4 and my 135/3.5, and it has 1:1 at a bit more comfortable working distance, thus solving a bunch of problems at once.<br><br>I also looked into Ring flash and extension tubes. If memory serves extension tubes take away your ability to focus to infinity. Even if they don't, ring flash and extension tubes ad a level of cost and complexity that I'm just not ready to deal with. I also don't have a lot of expendable income at the moment and will have time to reconsider, so if there is a cheaper manual focus that offers the same benefits as the sigma, I'd be all over it.

<br><br>

Long story short, getting the sigma lens will be a total impulse buy =).

[david_barts2]

<p>You won't regret getting a longer macro lens. I put up with the disadvantages of only having a 50mm macro for years. Once I got the 100mm macro lens, it was such a convenience to be able to, for example, shoot a close up of a flowering shrub and not have to be so close that some part of my tripod or camera (or my body!) was physically touching some part of the bush and making the subject move.</p>

<p>I also have a set of extension rings which I use with a 200mm non-macro lens for those times when the 100mm lens doesn't give enough working distance (which isn't a common occurrence, but it's nice to have that option).</p>