Do Pro Nikon Zoom lenses behave this way?

[raymond_ocampo]

When I used to work with film (cinematography) lenses with Zeiss and the like I can be able to get focus by

zooming in and focusing on the subject matter I want in critical focus then zoom out with the proper

framing in mind.

 

Can I do this same method with Nikon zoom lenses (or any other high quality lens) for that matter? With

the focus point shift as I zoom in and out of the frame?

 

Thanks for the input.

[ronald_moravec1]

Sure, but it is not necessary as the subject stays in focus properly all the time.

 

The lens you refer to that loose focus as you zoom are called parafocal, not zooms. They

have not been made for 35mm still for decades. The original Zoomar was made this way.

[lex_jenkins]

Some Nikkor zooms may not be technically varifocals but they will go off focus a bit when zooming. The 35-70/2.8D AF behaves this way. The focus goes just slightly off when zooming. I suspect this is more a factor of the older AF screwdriver focusing mechanism than optical design.

 

AF-S Nikkors appear to retain focus when zoomed. But I haven't tried 'em all.

 

Most of the zooms I've owned over the years - including Canon FD, Minolta Rokkors and several third party zooms - were not varifocals.

 

I had a couple of Vivitar Series 1 28-90/2.8-3.5 that were varifocals, not true zooms. This was touted as a "feature" and "benefit" rather than a flaw. Fans of the lens said it enabled keeping the same framing on a moving subject by changing the focal length, and the lens would change focus to compensate. I liked the lens but never quite saw the benefit to that "feature." I prefer the reasoning offered by a former Vivitar employee who said it was simply more cost effective to build varifocals because there were fewer optical compromises involved. This makes sense because the philosophy Vivitar had regarding their Series 1 lineup was to design them without regard to cost, then build them as cost effectively (i.e., down to a given price point) as possible while retaining as much optical quality as originally intended.

 

I'm not sure about the 70-210/2.8-4 Series 1 zoom. Mine is packed away at the moment and I don't remember whether it's a varifocal or true zoom. Given the fact that it's a push-pull type using the same ring for focus and changing focal length, it's moot because it's very difficult to change focal length without also affecting focus.

 

BTW, that's not the reason why the 35-70/2.8D AF Nikkor *might* change focus slightly when zoomed. The large push-pull zoom ring doesn't serve double duty as a focus ring.

[vivek iyer]

See:http://www.photo.net/bboard/q-and-a-fetch-msg?msg_id=00BZ4d

 

I think Brian Caldwell's post there is particularly useful.

[kohanmike]

My old Vivitar Series 1 70-210mm (c1973, pre AI) focussed that way; zoom in, focus, stay

focussed at any zoom length. I didn't realize it was f2.8-4, I thought it was 2.8 all the way.

[lex_jenkins]

Michael, your 70-210 was probably a different version. Several variations were made in the approximate focal range of 70-210mm with different maximum apertures, some fixed, some variable, and there were several manufacturers involved.

 

Mine is a later AI (AI-S?) version and was actually manufactured by Komine if I'm recalling correctly.

[raymond_ocampo]

Thank you guys for all the replies. So based on the varied replies I guess there is no clear

indication whether one manufacturer alone does produce parafocal zoom lens exactly the

way they produce lenses for cinematography.

 

I would have assumed at least the "pro" version lenses of Nikon, Canon and the likes would

at least be produced in this way - that the area in critical focus will stay the same despite

the varied focal length of the zoom lens.

[lex_jenkins]

Raymond, all of the recent Nikkor zooms I've tried did retain focus when zoomed. This includes the 12-24/4 DX, 18-70 DX, 24-120 VR, 70-200/2.8 VR, 80-400 VR and a couple others that I can't recall at the moment.

 

However, frankly, I don't trust automation. So while I'll occasionally prefocus by zooming in, then going to a wider focal length, when I have the time I'll always recheck focus. Almost invariably I can see a tiny adjustment in focus.

 

It may not have anything to do with the lens. I'm just not convinced that any camera's autofocus is 100% reliable. For example, when using manual focus lenses on my D2H I focus by eye because the electronic focus confirmation aid is usually slightly off - not enough for casual photography, but enough to throw off macrophotography or fast lenses with shallow DOF.

[raymond_ocampo]

Lex, thank you for additonal info on Nikon lenses. I don't use auto focus because I don't

trust it. It focuses and decides on it's own which it wants to be in focus.

 

My problem is that when I think I've got the focus nailed on a person using 24mm, then

when I go zoom in at 70mm the person is actually off. So I have to zoom in, obtain focus

of the person then zoom out.

 

That darn viewfinder is just so small to get good focus. While I've thought about using a

magnifier, it essentially knocks out the frame coverage while only giving 15%

magnification.

 

In cinematography I measure the subject to the focal plane, but the distance marking on

the lenses are not too usable than the lenses used for cinematography.

 

But thanks for letting me know that Nikon lenses are at least reliable for helping me

obtain focus as I zoom in then out.

[Ed_Ingold]

Zoom lenses for cinematography are more nearly parfocal. In addition, the back focus can be easily adjusted (and must be adjusted) for a particular focus range. Video lenses with auto-focus are not so tightly specified, since the auto focus takes up any slack. This way you get better optical performance or a simpler lens than if parfocal were a priority.

 

It is always risky to zoom in to focus then zoom out, unless the lens costs about as much as an SUV. It is kind of a tradition amongst the uninformed with inexpensive cameras, and a poor practice in general.

[Ed_Ingold]

By the way, I have three Nikon f/2.8 zooms - the 17-35, 28-70 and 70-200. None are parfocal to except to a first approximation - just close enough to avoid a great change in the field of view (a characteristic of internal focusing).

[frank_skomial]

While preserving focus when zooming is very important for high end movie camcorders, it is less important for still type photography.

 

Good auto focusing system, e.g. top end Canon cameras, should refocus within a fraction of second and assure perfect focus picture, depending on auto focusing mode used during the final picture taking instance. Perhaps D3 and D300 will have improved auto focusing capabilities. Consumer grade cameras are much slower re-focusing after zooming, depending on mode and lighting/contrast/lens.

[russ_butner___portland__or]

Lex

 

Yours is the Komine model (#3).

 

Regarding Vivitar Series-1 glass. There are numerous (8) Series 1, 70-210 lenses. However, for the sake of discussion, we will deal with the first three. The following editions are nothing to seriously consider, so we will concentrate on the first three editions, which are the good one's. The 4th & 5th editions are also 2.8-4 variable aperture model's, but lacking in construction quality (Cosina built). Due to the fact that the third one is a variable aperture lens, (2.8-4) it will be somewhat sharper than a fixed aperture lenses. It is much easier to design and build a quality variable aperture lens. The first edition was designed by Vivitar (Ellis Betensky had a hand in it) and built by Kiron. (67mm filter) It is a professional caliber lens, with a 1:2 macro feature built into it. It was the first zoom, designed with the aid of computers, that truly rivaled the OEM lenses of the time. That was in "76."

 

The second edition (my personal favorite) was built by Tokina, per, Vivitars specs. It too, is a fixed 3.5 aperture, but smaller, lighter and sharper. (62mm filter size). I really like it because of the fixed 3.5 aperture which is nice for focusing in dim light and long range flash work. However, not a true macro, 1:4 life size.

 

The third edition was made by Komine, and like the first two, is very well built. It is a 2.8-4 variable aperture lens, and the sharpest of the bunch. It has 1:2.5 life size macro from 100-210mm's, with a working distance of about two feet. Which can be quite useful. Can you see a discernible difference in slides taken with either one of them? No! Don't get caught up in bench tests. Any of the first three editions will give you professional-publishable images. I really like this lens, and in time may become my favorite.

 

Personally, I recommend the second or third edition of the line. I have and use all three of the first editions, and can highly recommend any one of them. Superb optics and construction.

 

The Kiron 70-210 f/4 with zoomlock, is also a very good lens.

 

Russ

[Matthew Currie]

I thought originally that the designation "zoom" implied that the lens is parfocal, and note that my Kiron 28-105, which is not, is designated as "varifocal" rather than zoom. But I was quite surprised to find that my Nikkor 35-105 AIS, along with its other quirks, is not even close to parfocal, so it's clear that Nikon has not always considered it either necessary, or a qualification for the "zoom" label.

[lex_jenkins]

Raymond, if you don't need autofocus you might prefer an AI, AI-S or even an AF Nikkor. In my opinion the manual focus feel of AF-S Nikkors is pretty poor - these lenses really aren't designed for manual focusing and feels more like twisting the lid off a medicine bottle than like a well damped manual focus lens.

 

AF Nikkors still aren't quite as nice for manual focusing as a good AI or AI-S, but there's none of that weird ratcheted feel of an AF-S Nikkor focus ring.

 

Unfortunately the selection of top notch manual focus Nikkors is somewhat limited. As Nikon transitioned to autofocus lenses they also improved the optical design. So to enjoy the optical performance of something like the 70-200/2.8 VR AF-S or 28-70/2.8 AF-S you'll also have to learn to live with the less than optimal feel of manual focus.

[raymond_ocampo]

Lex, that's exactly what I was thinking. I wanted the old Nikkor lenses with the manual feel

of an exact engineered piece. Not some slippery never-ending ring. However, as you

pointed out I'm also after the optical improvement of the new lenses. What a dilemma.

[Ed_Ingold]

What is this nonsense about a "ratched feel" to the focusing ring in AFS lenses. The only thing even close to this description occurs when the focusing mechanism reaches its mechanical stop while the focusing ring continues to turn with increased friction.

 

To the contrary, I find the manual focusing action of my AFS lenses to be smooth and with a much longer throw than on conventional AF lenses (such as the 28-105 or 35-70/2.8). When you turn the ring, the AF automatically disengages even before lock is achieved. Unlike most conventional AF lenses, the focusing ring does not turn during AF operations.

 

Manual focus lenses are fine for copy work, landscapes, closups and other leisurely activities. For anything else, AF trumps MF. Things were never so good as some seem to remember.

[vivek iyer]

"I find the manual focusing action of my AFS lenses to be smooth and with a much longer throw than on conventional AF lenses (such as the 28-105 or 35-70/2.8)."

 

Good for you! That doesn't entitle you to call someone else's preference as 'non-sense'.

 

"Manual focus lenses are fine for copy work, landscapes, closups and other leisurely activities."

 

Interesting thoughts. What would be 'non-leisurely' activity in your view?

[oskar_ojala]

<i>In cinematography I measure the subject to the focal plane, but the distance marking on the lenses are not too usable than the lenses used for cinematography.</i>

 

<p>This is true for quite many AF lenses, but quality MF lenses tend to be spot on with their markings.

 

<p>Whether you need and AF zoom for the latest technology depends a bit on your are of interest. In general though, it's true that the latest AF-S zooms are better than their MF predecessors. If you want to go MF, you should consider primes.

[inventory-photo]

The only lens I am sure shifts focus when zoomed is the Sigma 170-500mm, although other lenses that profess to hold focus may still shift a little when zoomed in my experience.

[raymond_ocampo]

I appreciate all the constructive comments. Thank you, guys.

 

Oskar, yes I do love working with primes as lens distortion is close to nil (if present at all).

However, cost is too much and I'm waiting for Nikon to revamp their line with the Nano

coating.

[raymond_ocampo]

I have a 24-70 lens on order and I'm excited to see how this behaves compared to the 28-70

lens I use. Crossing my fingers the focus holds much better.

[lex_jenkins]

I've rechecked my AF-S Nikkors and noticed distinct differences in manual focus feel. The inexpensive 18-70/3.5-4.5 DX doesn't have a particularly objectionable manual focus feel. I wouldn't say it's equal to a well damped manual focus lens, but it's not bad.

 

The 24-120 VR is one of the more objectionable lenses in terms of manual focus feel. It muted ratcheted feel of tiny plastic nubs rubbing over each other. Not a big deal since I never manually focus this lens.

 

But folks who may prefer to occasionally manually focus an AF-S Nikkor should test the feel carefully to determine whether it suits their preferences.

[oskar_ojala]

Raymond, you can always buy second hand MF primes. The cost is quite reasonable if you don't need anything exotic. The Zeiss ZF series of lenses is very nice if you want new lenses, but they cost the amounts that quality lenses cost.