D750 & Tokina AT-X 100mm f/2.8 PRO

[marcello dasilva]

<p>So this is my 1st DSRL FX after I sold my F100 about 10 years ago.I need to get used to this new gadget,but I got a Tokina Macro 100mm 2.8 and works fine as a portrait lens very fast but when I tried to use as macro,insects.flowers etc...This lens hunt for focus forever.Don't know if is user error or the lens,also sometimes doesn't go to 2.8 only 3.0.</p>

<p>Thank you</p>

[rodeo_joe1]

<p>Maybe the hunting is because the lens is out of its focus range. Even macro lenses won't focus beyond a certain close limit, and for a 100mm macro lens that's going to be around 150 to 170mm from the front of the lens. Macro lenses often have a focus limit switch as well, which prevents them from using their full AF range. Check that focus limit isn't engaged.</p>

<p>It's common for macro lenses to show a smaller aperture at close focus. The reason being that the effective aperture decreases as a lens is extended to focus closer. That's perfectly normal, and at 1:1 a macro lens will typically lose 2 stops of aperture; i.e. an f/2.8 lens will become an f/5.6 lens at "lifesize" magnification.</p>

[chip_chipowski]

<p>Like Rodeo Joe said, some (all?) macro lenses show you the effective aperture. My Tamron 60mm only shows f/2 around infinity. If my focus distance is relatively closer - like 10-15 feet, the effective aperture generally reads 2.2 or so, even when wide open. </p>

[jose_angel]

<p>I`m not an expert on lens design and optics, but this is my take. The AF system needs some kind of contrast or anything to catch focus. At very close distances, the amount of blur is enormous (DoF is so shallow) so it is very difficult to have something to catch hence it is normal to show some hunting. Camera shake also contributes to provide more blur to the AF system (try to hold the camera steady).<br /> I have read many people think this is a lens failure, but up to a certain reasonable amount, it is perfectly normal.</p>

[eric_arnold]

<p>i have the tokina 100. both things you're describing are normal behaviors for a typical macro lens. sometimes manual focusing is more effective at close ranges, and the tokina has a focus clutch which makes MFing relatively easy. </p>

[mike_halliwell]

<p>Are you using Live View to focus or the traditional View Finder?</p>

<p>Some of my early* Sigmas work perfectly in VF AF, but hunt and fail using LV AF. They had to be re-chipped by Sigma to work with my D5300.</p>

<p>Some of the 'improvements' Nikon made to recent DSLR bodies mean comms to older non-Nikon lenses are unstable/incomplete/compromised.</p>

<p>*including my Sigma 50mm 1.4 HSM (non ART), 10-20mm HSM, 100-300mm f4 HSM, 30mm 1.4 (non ART) HSM and 50-150mm 2.8 (non OS) HSM.</p>

[Wouter Willemse]

<p>Anything but infinity, my Tokina 100m macro drops to f/3 immediately, instead of f/2.8; at closest focus distance it's f/5.6 indeed. As explained above - completely normal.<br>

The Tokina has a focus limiter, which is really useful, but still the focus throw on the macro-end of things is long, so it is sluggish and indeed tends to hunt quite easily. The results are worth it, though - excellent lens.</p>

[andylynn]

I have the same camera and lens combination. It does hunt if trying to AF at very close distances. But it's really not

different from other SLR and macro lens combinations I've used. For macro, manual focus is better.

 

You don't have the limiter turned on with the lens focused at far distances, do you? That would prevent macro use

entirely.

[allan_jamieson2]

For macro photography learn to love Live View and turn off autofocus completely, you need the full control you get from choosing where

your lens is focused and not letting it try to focus by itself, where it will often go in and out of focus as it can't quite work out what to

actually focus on, only you know that bit, that's where your vision and creativity count!

[mike_halliwell]

<p>Marcello, are you out there?</p>

<p> </p>

[marcello dasilva]

<p>Yes I'm here,and yes I was focusing to close to the subject.Now I know.</p>

<p>Thank you</p>