Zeiss 85/1.4 - Is it hard to focus?

[davidfung]

Just wondering, I have been using my 50 1.4 and for close focusing (less than 3m) the plane of focus is awfully narrow. And when using a split image with matte screen, the image can look rather sharp in the matte section , only to be not correctly focused in the split screen. In principle, a 85mm with the same focal ratio should be even harder to focus, due to the even narrower focal plane. Is that the case. And if so, what are some of the problems and experiences people have had?

 

[dfm]

I have recently purchased an 85 1.4 and have really not had much time with it - but my initial experience, and compared directly with the 50 1.4 and 135 2.8 is that it is indeed very difficult to focus, at least in low light. I expect this will improve with experience with the lens but that's my two cents worth at this point.

David

 

[edmond]

I have 1.4/85, 1.4/50 and using ARIA and recently got an AX. Yes, the plane of focus is very narrow for these two lenses and I found it very difficult to get in focus picture for 1.4/85 up to f2.0 at mid to close range. You can¡¦t trust the split image nor the microprism from mid to close range focusing as it will give you a false result. At long range, I found the split image and the microprism will give the correct reading.

I used to have Canon FD1.2L/50mm and FD1.2L/85mm (both have floating systems) for more than 10 years and have no problem in using microprism for mid to close focusing. I guess the lack of floating system in Zeiss 1.4/85 and 1.4/50 will induce minor shift of focus for image formed by the outer f1.4 to f2.0 lens region in close range focusing which in turn induce a wrong focusing indication when using microprism or split image.

Matte section would give the correct focusing indication but as you would see these two lenses are indeed not such sharp at wide open and especially for close range due to lack of floating system, it is very difficult to judge the in focus position from matte section. ARIA would be better as it has a larger screen magnification ratio. I used the F-2N magnifier to judge the sharpest focusing position from the matte section in close range at about 1.2m. The test photos confirmed that the selected objects are all in focus.

I also found that the focusing screen for AX and RX are at a different orientation. The fresnel lens of the focusing screen for AX is orientated in a different way as compared to ARIA and the traditional way by other brands¡¦ camera like EOS.

For most cameras, the fresnel lens of the focusing screen is designed on the side between the mirror and the focusing surface (i.e. image will pass through the fresnel lens before reaching onto the screen focusing surface). But for AX and RX (FW type screen), the fresnel lens is designed behind the focusing surface. I am not sure whether the cause of the shift of focusing for the 1.4/50mm is due to the design orientation of ARIA screen as I haven¡¦t carried out any further verification with my AX but it might be possible that the fresnel lens could induce further focus error for split image part in close range.

I used to rely on microprism for precise close range portrait face focusing, as split image cannot tell precisely which part of the face is in focus. But I found that for ARIA, there is no central microprism disk. For AX and RX, the design of FW-2 central microprism disk is not as good as Canon where it will be more difficult to judge the in focus position for low contrast object.

Hope it is useful for you.

 

[nicolas]

Hi Edmond,

Did I understand you correctly that images which appear in-focus on your split image focusing screen, do not produce in-focus images on the film?

From what I understand of camera design, the distance to the fresnal (and split image prism) are the same as that to the film plane. If one is in focus and the other is not, either your film pressure plate, film flatness or the focusing screen are not in their proper place. All reputable camera companies build SLR (manual focus bodies) to work in this way.

The orientation of the screen is not relevant, because the screens are designed specifically for these SLR bodies and will have the correct distance to fresnal same as the distance to film plane. That is why there are specific screens for specific bodies and we cannot modify (eg. cut the corners, etc) of one screen and use it on another body. The thickness of the screen and which side the fresnal is on (top or bottom) have their design reasons.

An outside possibility is that your built-in diopter is not adjusted properly for your eyesight.

Floating systems (I assume you mean floating elements) do not vary the focusing accuracy of the body. Floating elements improve the color & contrast produced when a lens is focused near - but that's another discussion.

A bit on the AX and RX since I have owned both of them:

I have seen a few AX bodies where the AF focus does not tally with the split screen exactly. This is due to the alignment of the sensor and/or the focus screen being unequal, but its not a big deal and hardly noticeable in most photos. One of the reasons most consumer AF SLR's don't have split screens - confusing, unnecessary (among the many reasons....).

The RX & AX have 20% dimmer viewfinders than the Aria, 159mm, etc because the mirrors used in the AX & RX allow only 80% of the light to be reflected to the prism, the other 20% is directed to the AF & DFI sensors. So the issue is not the focusing screen, but the bodies. The same screen FW2 is used on the ST and RX2 (which has no DFI), I think you'll find it works at least as well on those bodies as your Can*n experience

Also, Can*n uses a totally different type of focusing screen, which is brighter, but gives less contrast - good for AF and low light subject framing.

On the 85/1.4, its a joy to use and not difficult to focus at all at 1.4. I've used it on a Yashica FX 103 also and had stunning results. If anything, the problems for accurate, in focus shots is the photographer's body movement. If the subject is still and you're using a tripod, the accuracy of focus of this lens is not an issue.

David's question about being in focus in the matt area but not the split image - i would trust the split image because that is what the designers want the user to use. The matt area best used only to frame the subject. There are specific screens like the FW5, used for close-up work and may be what you need.

Hope this helps and happy shooting.

 

[mike_nunan]

Hi David,

Regarding depth of field, there is a common belief that longer lenses provide less DoF at a particular aperture. While this is not wrong per se, it's not necessarily the most useful way to think about it. DoF is very directly related to magnification factor, regardless of focal length. So, if you shoot a head-and-shoulders portrait where the lens takes in an area of about 1m width at the plane of the subject, this gives a magnification of about 1/27th (a 1000mm subject width reduced to 36mm width at the film plane). The DoF at, say, f/4, will be almost exactly the same whether you uses a lens of 50mm, 85mm or even 300mm focal length, PROVIDED the same framing is used. Obviously longer lenses allow tighter framings at the same distance, so if you're already using your 50/1.4 lens at its closest focus then you can venture into even shallower DoF waters with the 85. However, if you get a feel for the available depth of field at various apertures and framings with your 50, you can transfer that knowledge to other focal lengths as necessary. I only recently came to understand this (with thanks to Norman Koren's excellent site) and it was something of a revelation, as it has taken much of the guesswork out of aperture choice and makes it much easier to be comfortable with the lenses I use less frequently.

HTH

-= mike =-

 

[davidfung]

Mike, I am aware of the relationship of DOF and focal length. I think though, for focusing purposes, the apparent plane of focus is much less than a 50. As they are both 1.4, the circle of confusion will be very similar. However, because the 85 has a smaller FOV, as you mentioned, hence, a higher magnification. Therefore, the COC, or airy disk, would be larger. Therefore, the of close focus would be greater. However, it is all fine in theory, but is it more difficult to focus with the 85?

For ex&le, is it hard to get a critically good focus on a subject's eyes say 3m away?

 

[mike_nunan]

Hi David,

> is it hard to get a critically good focus on a subject's eyes say 3m away

At 3m it's not going to be too bad. At that sort of range we're talking about an upper-body portrait (I'm going to couch all this in terms of portraiture, simply it's what I do most of) and you have about 10cm DoF at full aperture, according to the standard calculation based on a 1/100" disc on a 10x8 print. Obviously that is over-optimistic if you want critical sharpness, but bear in mind that the 85 is pretty soft at full aperture anyway, so this may be a moot point.

Go in for a tighter shot though, and things change dramatically. At 1.5m the DoF is cut to 2.5cm and at 1.2m you're down to just 1.6cm, and it becomes difficult to get both the subject's eye's sharp unless they are looking at you dead-on. Accurate focus in handheld shots with moving subjects becomes very difficult at this sort of magnification. Also note that AF cameras don't offer much help, since they lock onto the end of the subject's nose. [Aside: why doesn't any AF system provide some kind of "focus offset" feature to help out with this?]

Just for comparison, the 85 at 3m gives you the same FOV as the 50 at 1.76m, and if you plough that into a DoF calculator you will see that you get the same 10cm figure for the depth. Similarly the equivalent to the 85mm @ 1.2m with the 50 is 0.71m, and again the 1.6cm DoF figure arises. So basically you are in a position to establish yourself how the 85 will behave at any given distance. Just try it with your existing lens at whatever distance multiplied by 0.59 (i.e., 50/85) and you will have the same framing and DoF, although obviously the perspective will be different.

BTW, for all these calculations I have been using Bob Atkins' calculator at the following URL:

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HTH

-= mike =-

 

[simonli]

"what are some of the problems and experiences people have had?"

problems - difficulty in getting focus WHERE I WANT eventually.

solutions - lots of practice; anticipate movement; shoot aplenty; step down to 2.0 or 2.8 for pics that don't 'require' 1.4 using DOF preview; shoot from further distance to 'increase' DOF; shoot 2 images - one sharp @ 5.6; one 'blur' @ 1.4; selectively merge with Photoshop;

Last but not least, attempt BLURRED pictures.

 

[simonli]

Couldnt upload in previous post.
Here's a great ex&le, courtesy of Marc Williams,

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[rico]

Agree with simonli, Mike, and nicolas. The P100 wide-open is a bear to focus at 1m. DOF is a fraction of an inch, and photog body sway is a serious issue. Some solutions: use a tripod, strap your subject down, bracket your focus, stop down, pray.

Even the P50 @ f/2 is critical at 1m:

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[afranklin]

> "what are some of the problems and experiences people have had?"

I use the 85/1.4 routinely, and have no problem getting critical focus wide open...if I'm paying close attention to my technique. I move my body forward and backwards to get critical focus, and try to brace not only the camera, but my body, in such a way that I am stable as to not effect focus as best I can. In some shots, I don't get what I wanted, but in most I do. I also have the 100/2, and don't find it any more difficult to focus, but I prefer the 85/1.4.

There are basically two Contax lenses I use the most, the 85/1.4 and the 35/1.4. If I had to pick only two to have, those two would be them, unquestionably.

Regards,

Austin

 

[tom]

Please compare the 100 f2 with the 85 1.4. Thanks

 

[wojo]

The 85 and poor light is a tough combination, it's not the sharpest lens wide open even if you hit the focus perfectly. I've pretty much given up using the split image, microprism "focus aids". The matte area just off center works better for me, your milage may vary.....
The softness can really work to your advantage though, it evens out skin tones, makes for a more pleasant picture. The 85 has the nicest bokeh, soft focus whatever you want to call it of any lens I've used. Critical areas such as the eyes, lips, and hair can be selectively sharpened in any competent editing program. Facial pores really need little sharpening ; )

Joe W

 

[rico]

Joe,

I also find the ground-glass matte to be ideal for softer subjects like portraits. In fact, I'm thinking about switching the screen on my Aria: when you don't want the split-image rangefinder, it really gets in the way.

 

[mike_nunan]

Yeah, I'll second those comments about the ground glass. When I replaced my sadly-demised RTS body with an RTS II, the new camera came with a matte grid screen. I was planning to change it to a diagonal split, which is what I had on the old camera, but after a few shooting sessions I decided not to bother. The matte area is great for focusing the fast lenses and the grid is a surprisingly big help during composition.

 

[afranklin]

Hi Joe,

> The 85 and poor light is a tough combination, it's not the sharpest > lens wide open even if you hit the focus perfectly.

That is pretty much opposite of my experience. I find because this is an SLR, and the max aperture of the lense is what dictates how dim the viewfinder is, the 85/1.4 is far easier to focus in low light situations than most any other lense for this camera, but I have no experience with the 1.2. I also find it quite sharp at 1.4...and the MTF charts for this lense seem to confirm my experience, and show it's actually better than the 50/1.4 is wide open. BTW, the 85/1.4 is one of the highest rated lenses by photodo...with a "grade" of 4.6.

> I've pretty much > given up using the split image, microprism "focus aids".

As you said, your mileage may vary...and I find the split image with a microprism collar works great for me!

Regards,

Austin

 

[mike_nunan]

Austin is right that the lens does have one of the best overall scores on Photodo, and it holds its own at f/1.4 compared to other fast lenses, but you still have to be reaslistic about the level of sharpness you expect wide open.

I recently posted some ex&le images to Photo.net that illustrate the level of softness this lens can produce at full whack. Have a look at the following page (search for the words "glowing reports" and you'll get straight to the images):

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The crops are reduced to 25% from the original scan and still the softness is very evident. The aggregate Photodo score for the 85 at f/1.4 is 0.63, which is to say roughly 60% contrast remains on average at that aperture. Compare that with the approx 85% contrast available between f/2.8 and f/8, and you can see that this lens is far from its best wide open. However, the wide aperture does make it a doddle to focus accurately when you're stopping down a bit, as Austin says.

If I'm plan to shoot at full aperture and I want sharpness, I actually prefer to use my Canon EF 85mm f/1.8. Although it's not quite as fast as the Contax, it's considerably more punchy. Alternatively I'd use the Canon 135 f/2 which is _really_ punchy at f/2. I've heard great things about the equivalent Contax lens, so that might be a good alternative for those who don't use Canon gear, although I don't know anything about its wide-open performance specifically.

HTH

-= mike =-

PS. The first message in that Photo.net thread contains another ex&le image from the 85, showing how shallow the DOF is at full aperture at head-and-shoulders portrait range.

 

[afranklin]

Hi Mike,

> If I'm plan to shoot at full aperture and I want sharpness, I actually > prefer to use my Canon EF 85mm f/1.8. Although it's not quite as fast > as the Contax, it's considerably more punchy.

How does it compare to the Contax 85/1.4 at 1.8?

> Alternatively I'd use > the Canon 135 f/2 which is _really_ punchy at f/2. I've heard great > things about the equivalent Contax lens, so that might be a good > alternative for those who don't use Canon gear, although I don't know > anything about its wide-open performance specifically.

I have both the Canon 135/2 and the Contax 135/2. Though the Canon is a fantastic lense, the Contax 135/2 is the best of the best. It is a superb lense at 2, and equally as superb anwhere else. There is a reason it is one of the most expensive Zeiss Contax lenses out there...

Regards,

Austin

 

[rmiraniaolcom]

>>Alternatively I'd use the Canon 135 f/2 which is _really_ punchy at f/2. I've heard great things about the equivalent Contax lens, so that might be a good alternative for those who don't use Canon gear, although I don't know anything about its wide-open performance specifically. <<

Though I respect Austin's opinion and love the 135 myself, I'm not crazy about it at f2...it really does much better at f4 and shines exceptionally beyond f5.6.

I don't know that I've encountered any Zeiss lenses that I find worth shooting wide open --though I'm speaking mainly of handheld shooting and lenses longer than 50mm, which are what I mainly shoot with. In general, the type of shooting I do with 35mm makes it too much bother to open up beyond f2.8 or so...the paper thin depth of field is a big issue without a tripod and with my subjects moving...for concerts and evening portraits/candids, blowing the focus is much more likely for me than the lack of sharpness wide open.

The "punchiest" lenses I've had a chance to use at f2 or wider are the Contax 85mm 1.2 (very sharp at f2, decent at f1.4) and a Nikon 105mm f2 DC...but again, acknowledging it may be my technique or bad eyesight, I find it a bit of a tightrope act trying to nail focus with my subjects at such wide apertures.

I do prize these lenses when shooting events outdoors as daylight turns into evening, as their speed does allow for reasonable shutter speeds to be maintained, and they provide better color and contrast relative to other lenses I have, even if the sharpness or focus is slightly off as the light grows rapidly dimmer.

Besides sharpness, there are very nice selective focus and blurred background effects that can be gained shooting at wider apertures, of course. But when I want that type of look (and I have some control over how much my subjects move!) I'm much more likely to use medium or large format.

 

[davidfung]

Hi, thanks for all the input! To clarify a little bit more. I intend to do three things with the 85/1,4. Shoot candid portraits, indoor low-light concerts, meetings, etc, and astrophotography. The 1.4 is only critical for smaller DOF for portraits, higher shutter speeds for indoor, and a larger useable aperture for astro stuff (like 2.8). My question is, is the 85/2.8 better served for these purposes, or is the 1.4 really worth the stretch?

For ex&le, is a 1.4 DOF really much, much more than 2.8 at 3-5m subjects?

Does the softness at 1.4 detract from images? Or is camera shake more of an issue? (Say 1/60 @ 1.4, and 1/15 @ 2.8.

Is the image of the 1.4 at 2.8 really better then 2.8 in terms of sharpness, coma, chromatic aberrations and the other seidel aberrations?

Thanks so much!