APO or Non-APO, is it worth it?

xtolsniffer · May 15, 2008

I'm looking to extend the range of lenses in my Mamiya RB system, the longest I currently have is the 140mm Macro which is great but not quite long enough to isolate flowers against an uncluttered background. In 35mm I would usually use a 200mm macro for this, so am looking at the 250mm (about 120 mm equivalent focal length/angle of view) or the 350mm (equivalent to 170mm on 35mm). At the moment I'm erring towards the 250mm. The new KL version of the 250mm comes in two flavours, APO and non-APO, one being twice the price of the other. Is it worth it, does the APO really make that much difference? Of course there are quite a few Sekor C 250mm's floating around as well, I don't know how these perform compared to the KL versions. Any advice would be most welcome!

Chris Breitenstein · May 15, 2008

If the lens is not APO then each color within your flowers are going to focus on a different plane. Are you using an APO lens now? If i were you I would try and keep all my equipment as homogenous as possible. Although it is important to understand the effects that different features will have on the final product/print, and to find equipment that fits your vision completely and thoroughly; keeping you equipment consistent allows you to more accurately predict how everything will respond in any given scenario. this is important because it means you shoot less film in order to produce a given number of photographs, and allows you to keep track of your variables more easily.

If you are working with an APO lens now and you are happy with it, then buy an APO macro. Better yet, borrow one from a friend. You get to check out a new lens, and see how well it works for you before buying one.

I hope I was of some help.

yours;

keithwms · May 15, 2008

Apo is worth it if you plan to drum scan right to the edge of enlargeability or if you might put a ZD or similar back on it eventually. Bear in mind that even the costliest rb lenses are a fantastic bargain right now. I just don't see the point in buying a pre-KL lens right now, unless finances are a major issue. But any of the newer RB lenses offer tremendous bang for the buck.

The 210 KL is, in particular, one of the very best MF lenses on the market. Take into account that you can shoot 6x8 with it on the rb and it arguably is the best.

I might be interested in your 140 macro if you are putting it up for sale, by the way

skahde · May 15, 2008

So much about the theory behind it. In reality a lens carrying the Apo-designation is a claim by the manufacturer refering to a higher level of quality. If you have a look at e.g. the specs for the Rodenstock Apo-Radagon 2,8/50mm it has very high resolution and very good contrast but its most prominent abberration is longitudinal colour i.e. it is not focussing all visible colours in the same plane of focus.

Some lenses actually do fit the above definition but your'e better of checking the actual type of lens (or even sample) if the Apo-feature is important to you.

best

Stefan

Nicholas Lindan · May 15, 2008

xtolsniffer said:
APO and non-APO, one being twice the price of the other. Is it worth it

In general an APO lens is better corrected.

The upside is that the better correction allows the lens to be used at wider aperatures. This in turn allows the lens to have higher resolution because it is no longer as diffraction limited.
The downside is the depth of field is reduced.

The result is that less of the image is sharper.

For enlarging and copy work with process cameras - where depth of field isn't an issue - this trade-off makes sense. For 3-color copy work the apo color correction is needed to keep colors in registration. To take advantage of the increased resolution it is usually necessary to use glass or vacuum carriers and maintain precise alignment.

Apochromatic correction in a camera lens may be worthwhile where depth of field isn't that much of an issue and you can use a wider f-stop to take advantage of the increased resolution. Many apo camera lenses (Rodenstock being the prime example) aren't, strictly speaking, apochromatic, though they are extremely well corrected for color aberrations; in these cases 'apo' is an indication of a higher grade of lens.

To see any improvement you will need a tripod and precise focusing with a 6x magnifier. With an SLR the collimation-mirror alignment needs to be perfect because depth of field will be zilch and mirror lock up is probably mandatory.

panastasia · May 15, 2008

Interesting info on APO and non-APO, thanks Nicholas.

I have the 140macro, 180, 250 and 360; all non-apo KL, and like them all, equally, as a set. I know that's not saying anything for a comparison but I like keeping with the less exotic, and more familiar. I have no desire for the APO types because I'm sure I wouldn't notice, or appreciate, the difference in performance of one type over the other. If the depth-of-field is reduced with the apo types, I would probably notice that.

Q.G. · May 15, 2008

Nicholas Lindan said:
In general an APO lens is better corrected.

The upside is that the better correction allows the lens to be used at wider aperatures. This in turn allows the lens to have higher resolution because it is no longer as diffraction limited.

The downside is the depth of field is reduced.

Just so this is not misunderstood: this, of course, is the downside of using a lens at wider apertures.
Not of being better corrected.

edz · May 15, 2008

Nicholas Lindan said:
In general an APO lens is better corrected.

The upside is that the better correction allows the lens to be used at wider aperatures. This in turn allows the lens to have higher resolution because it is no longer as diffraction limited.

The downside is the depth of field is reduced.

No. APO does NOT means better correction to be used at wider apertures. APO does not mean faster. The fastest and highest resolving lenses I know are NOT APO. Apochromats (and most so-called APOs are not) have higher levels of color correction. True apochromats are designed to bring three wavelengths into focus in the same plane. They don't need to provide higher resolution nor better correction to any aberration other than chromatic to be a true APO. Many APOs I'm familiar with are, in fact, designed to be used at rather small apertures and provide low levels of spherical and chromatic aberration but less than stunning resolution.

xtolsniffer · May 16, 2008

Wow, thanks for that folks, a very useful discussion. I get the feeling that the APO tag may not be worth spending twice as much on a lens - especially since about half of what I shoot is black and white anyway, where chromatic aberration is not exactly the main consideration. All I have to do now is decide between 250mm and 350mm. I've never really liked a 135mm focal length on 35mm, so the 250mm on 6x7 is looking less likely. Of course I could just save my pennies, use the 140mm and just get closer to the subject!

Dan Fromm · May 16, 2008

Um, er, ah, chromatic aberration can be as bad a problem with black/white as with color. It makes it impossible for the plane of best focus to be in perfect focus. Before color film was available there were soft focus lenses, e.g., the Boyer Opale, that used chromatic aberration to get the soft focus effect. According to a friend who has several, Opales produce horrible effects on color film ...

But the OP's question wasn't a vague general question. It was whether the difference in performance between two 250 mm lenses, one engraved "APO", the other not, in the Mamiya RB system justified the APO's higher price. None of the answers so far addressed the question directly, but one, from panastasia, pointed out that panastasia's non-apo RB 250 is a good lens.

xtolsniffer, since it seems that no one here has shot the two lenses you're considering against each other and since none of us is exactly as exacting as you are, you'd do best to rent both, if possible, and run the test yourself.

2F/2F · May 16, 2008

I would say that for 90% of common photographic uses, and for someone with an average income and budget, the APO designation is not worth twice as much. Even lenses that are older than dirt are FINE. The best photos ever were taken on lenses that don't come close to the on-paper quality of today's lenses.

Have you simply tried extension tubes? Not the same effect as a longer lens, but they will help quite a bit. Oh yeah. They're cheap in comparison as well.

Lee L · May 16, 2008

The "three wavelength correction" information that edz supplies is a correct description of traditional APO design. It doesn't guarantee, however, that the term APO is used consistently by manufacturers to mean exactly that, and the degree of difference between APO and achromatic designs varies as well.

My only experience with a direct comparison of APO vs non-APO within a brand was with 180mm focal length lenses for Leica R, comparing their 180mm f:3.4 APO aerial reconnaissance lens (designed for military, but made available to the general public) to a regular 180mm lens. I don't recall if the regular lens tested was their f:4 or f:2.8, it was 30 years ago. The comparison shot was of the back of a car across a parking lot shot on Kodachrome 25 and the camera on a tripod in full sun, with specular chrome highlights off the bumper. There was a sticker on the bumper with fine print, a parking permit with multiple colors and black text. That sticker was much better defined in the APO shot, with no color fringing and text that was much easier to read. The non-APO shot wasn't bad, but at high magnification, the APO clearly outperformed it.

That particular 180 APO was designed for performance at greater distances (being an aerial recon lens) and Leica provided their 180 f:4 with a helical that focused closer because it performed better at short distances.

An APO should perform better than a non-APO from the same maker in both B&W and in color, but not all APOs are designs that truly fit the classic definition, being more ad hype than achieved design goals. APOs often contain extra corrective elements, special refractive index glass, or aspherical elements to achieve APO performance. That drives the prices higher. There are also other aberrations besides chromatic that contribute to a lens' performance, and those have to remain well corrected.

The term APO has been stretched (if not abused) in many products, but many others do meet the classic definition, and are clearly better than their achromatic counterparts. The proof is in the negative/transparency. Sorry I can't help you with direct experience or second hand reports on the Mamiya gear.

Lee

xtolsniffer · May 16, 2008

Thanks chaps, I'm assuming that the APO designation means that there is some element in the optical formula which reduces chromatic aberration in this longer focal length lens. I was just wondering if this improvement would actually be visible in a real photo rather than just on an optical test bench. I'm slightly suspicious as the Mamiya lenses are already very very good, and I wonder if I'm likely to notice the differece. For example, the floating element in the 65mm Sekor C is supposed to ensure edge to edge sharpness, so I ran some tests, taking shots of a piece of printed text at 1 m distance, and setting the floating element to 'infinity', then to '1m', exposures were flash, tripod mounted, mirror lock-up on FP4. I enlarged the neg to a 16"x20" print and I'm damned if I can see the difference where the floating ring was set. I can see the tiny smudges of ink on a piece of font size 16 printed text at a meter, but no real difference between the two. So I figure they are already very good lenses and any improvement would be beyond my powers of observation!

panastasia · May 16, 2008

Lee L said:
The "three wavelength correction" information that edz supplies is a correct description of traditional APO design. It doesn't guarantee, however, that the term APO is used consistently by manufacturers to mean exactly that, and the degree of difference between APO and achromatic designs varies as well.

My only experience with a direct comparison of APO vs non-APO within a brand was with 180mm focal length lenses for Leica R, comparing their 180mm f:3.4 APO aerial reconnaissance lens (designed for military, but made available to the general public) to a regular 180mm lens....
....That sticker was much better defined in the APO shot, with no color fringing and text that was much easier to read. The non-APO shot wasn't bad, but at high magnification, the APO clearly outperformed it.....

An APO should perform better than a non-APO from the same maker in both B&W and in color....

Lee

At high magnification the difference should be apparent. The comparison of two 180mm lenses in 35mm format would be similar to a comparison of the 360KL and the the APO 350 Mamyia lenses. I would expect to see, at high magnification, a better performance by the APO 350 over the non-APO 360 but not such a difference between the those in the shorter focal lengths, such as 210 - 250, APO vs non-APO.

The need for APO designs - to correct for chromatic abberation - increases as focal lengths increase from 200mm in MF. This is the reason why there are no APO lenses offered in focal lengths less than 200mm (Mamyia RB). The correction isn't needed.

Paul

Chazzy · May 16, 2008

panastasia said:
The need for APO designs - to correct for chromatic abberation - increases as focal lengths increase from 200mm in MF. This is the reason why there are no APO lenses offered in focal lengths less than 200mm (Mamyia RB). The correction isn't needed.

So it's focal length that matters, not magnification? Would you mind saying more about this? I'm fascinated.

panastasia · May 16, 2008

Chazzy said:
So it's focal length that matters, not magnification? Would you mind saying more about this? I'm fascinated.

Chromatic abberation (color fringes) are more difficult to correct for when designing telephoto lenses. It's a light refraction characteristic of these types of lenses - inherent in the design - and you might say that magnification does matter since it's synonymous with the longer focal lengths; telephoto lenses, telescopes, microscope objective lenses, etc.

Dan Fromm · May 16, 2008

Um, Panastasia, how about long focus lenses of normal construction, as for example most process lenses? I ask because I shoot a variety of process lenses, focal lengths 135 mm (too short to be included, here for completeness) to 480 mm with no color fringing or softness issues. Some have "Apo" in their name, others don't, all are very well corrected. And of course my tiny little 700/8 Questar of nothing at all doesn't have color fringing problems. Motion control is hard with it, though.

panastasia · May 16, 2008

Dan Fromm said:
Um, Panastasia, how about long focus lenses of normal construction, as for example most process lenses? I ask because I shoot a variety of process lenses, focal lengths 135 mm (too short to be included, here for completeness) to 480 mm with no color fringing or softness issues. Some have "Apo" in their name, others don't, all are very well corrected. And of course my tiny little 700/8 Questar of nothing at all doesn't have color fringing problems. Motion control is hard with it, though.

Dan,
I cannot answer your questions, I'm not an expert in optics, I was generalizing. Apo designs generally apply to the longer focal lengths in a lens series, designated 'telephoto'. I don't own any apo lenses and don't have any color fringing or softness issues with the lenses I own. I can say that they're all very well corrected, but to what degree? Good enough for me.

I consider Apo lens design to be at the cutting edge of the technology but the improved performance of these doesn't attract me. Double the price for slightly improved image quality doesn't fit my needs (or budget). I guess this is my answer to the original question the OP asked. "Is it worth it?"

Lee L · May 16, 2008

Dan Fromm said:
And of course my tiny little 700/8 Questar of nothing at all doesn't have color fringing problems.

Reflector/mirror optics with a corrector plate, right? There's no inherent chromatic aberration with reflector/mirror optics because there's no differential refraction of varying wavelengths when the light doesn't pass through varying materials with different refractive indices, air/glass/air. You can make a rainbow with a prism, but not with a front surface mirror.

Lee

cotdt · May 16, 2008

The Mamiya APO lenses are called APO because they use low-dispersion elements, same thing as Nikon ED glass, every lens manufacterer has a name for it. The APO designation does not neccesarily mean that the lens has no chromatic abberation, so it is still not a true apochromat. But I've found that the low-dispersion elements does help make a difference.

keithwms · May 16, 2008

Cotdt there are non-apo RB (KL) lenses that use some ED glass, and then there are apo lenses that are more rigorously corrected across the spectrum as described above. They are two different sets of lenses in the lineup, that's where the original question came from.

Regarding process lenses, a small caution: my understanding is that "apo" in this case means quite specifically that these lenses have no refocus in the near UV where the film would be predominantly exposed. So there's no guarantee that an apo process lens is really all that apo through the reds! (Nevertheless, I have found my apo process lenses to be useful right from near UV to near IR, with little or no refocus. Go figure.)

What people look for in "apo" has changed somewhat - nowawdays, because of quite noticeable fringing issues with reduced-frame Bayer sensors that require interpolation, apo takes on a quite different value. This issue if far less extreme with film... or foveon-type sensors.

Q.G. · May 16, 2008

Lee L said:
Reflector/mirror optics with a corrector plate, right? There's no inherent chromatic aberration with reflector/mirror optics because [...] You can make a rainbow with a prism, but not with a front surface mirror.

True. But alas, the "corrector plate" is a refractive device.

Most, if not all photographic mirror lenses do have indeed lenses (more than just the one, the corrector plate) as well as mirrors.
So no reprieve: chromatic aberrations are still there.

DJGainer · May 16, 2008

Is this discussion focusing too much on the abstract? I mean, unless you are shooting extreme macro, won't the depth of field usually include all the wavelengths of the general subject area?

Q.G. · May 16, 2008

DJGainer said:
Is this discussion focusing too much on the abstract? I mean, unless you are shooting extreme macro, won't the depth of field usually include all the wavelengths of the general subject area?

Yes, and no. Depth of field would be different for different colours of the spectrum...

Lee L · May 16, 2008

Q.G. said:
True. But alas, the "corrector plate" is a refractive device.

Most, if not all photographic mirror lenses do have indeed lenses (more than just the one, the corrector plate) as well as mirrors.
So no reprieve: chromatic aberrations are still there.

You are correct. The refractive glass element is used to correct other aberrations commonly found in "folded" or fast mirror systems. However, corrector plates tend to have a much lower differential between front and rear surface curves than achromatic refractor lenses and camera objectives, so they tend to introduce less chromatic aberration than compound refractor optics.

I'm more connected to the astronomical world than the photographic world when it comes to reflectors, so I tend to think of the classical Cassegrain and Newtonian reflectors. I'm not a big fan of and don't normally use Maksutovs, Schmidt-Cass, Schmidt-Newt, or other corrector-plate + mirror arrangements. However, I'll readily admit that they are extremely popular because of their form factors and economical production. (Questar isn't run of the mill on that front.) I'd much rather use a well made straight refractor or Newtonian, depending on the object. The corrector-plate + mirror designs almost always feel like a compromise to me.

Lee

APO or Non-APO, is it worth it?

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