Soft and hard pal's

[HIGHER PEAKS]

We use the following pal's in our office and i am wondering if someone could quickly catagorize them according to hard or soft? I understand the concept but dont know which are which. Thank you very much.

Gp wide
gradal top
gt2
brevety
summit ecp
summit cd
picollo
hoya id
zeiss individual

[joptician]

Call your Hoya and Zeiss reps if you have them. Hopefully if the moon, sun and stars are aligned right they can explain to you what you are looking for. My experience is that the lens reps know the marketing material but do not have the technical expertise to answer such a simple question.

Don't forget to also ask them about these designs and if they are a western or eastern style (where the progression begins).;)

[mike.elmes]

My understanding of hard vs soft design relates to the corridor boundaries...
How quickly you go from clear vision in the reading area to the distortion.(astigmatic power) Long corridor designs have more lens area to spread out the distortion. Many if not all of the newer designs such as the list above are a combination of hard and soft designs. Soft along the 180 boundary, where the wearer wants peripheral, and harder in the 90 degree along the reading area.

[TLG]

I get frequent requests for this information from my website visitors. I think there are two main problems with trying to categorize them;
1.) It is somewhat subjective - what I consider 'soft' you may not
2.) I don't think you will ever get any manufacturer to say their lens is a 'hard' design. I mean, it almost sounds like it hurts ;). Yes, they may say that their lens is 'optimized for... blah blah blah' but I doubt you would hear the word 'hard'.

That said, I'm interested in seeing how this thread goes as I'm guessing there are those on this board that may not only disagree, but have some very definite opinions of which lenses fall into each category.

[sharpstick777]

Personally I think the "hard vs. soft" debate is overly simplified, and with the new digitally processed lenses, also out of date.

Traditional progressives manage distortion differently. Some like the Essilor Natural lose reading and mid-range area as the add power increases, to help distance accuity. The Comfort on the other hand will always keep a wide reading area, but the distortion will push up as the add power increases for the expense of the distance peripheral vision. The Natural would be a soft design, the Comfort is considered by some to be a hard (but many would disagree). The Ziess lenses typically use a combination, a little loss of reading, a little increase in distortion, and little decrease in Dist peripheral accuity. A true hard design would keep a wide reading and good distance but the distortion would increase in the soft focus area with the add power. Most actually use a combination of different tecniques.

The new digitally processed lenses try to move the distortion so far off the center of view its actually cut off when the lens is edged, or the distortion exists only on the vitural blank.

I would classify your list as such (but these are debatable):

Gp wide (hard, but like Comfort)
gradal top (combined)
gt2 (combined)
brevety (combined)
summit ecp (soft, but combined in higher powers)
summit cd (combined)
picollo (hard)
hoya id (digital)
zeiss individual (digital)

Sharpstick

[optigrrl]

Personally I think the "hard vs. soft" debate is overly simplified, and with the new digitally processed lenses, also out of date.

Traditional progressives manage distortion differently. Some like the Essilor Natural lose reading and mid-range area as the add power increases, to help distance accuity. The Comfort on the other hand will always keep a wide reading area, but the distortion will push up as the add power increases for the expense of the distance peripheral vision. The Natural would be a soft design, the Comfort is considered by some to be a hard (but many would disagree). The Ziess lenses typically use a combination, a little loss of reading, a little increase in distortion, and little decrease in Dist peripheral accuity. A true hard design would keep a wide reading and good distance but the distortion would increase in the soft focus area with the add power. Most actually use a combination of different tecniques.

The new digitally processed lenses try to move the distortion so far off the center of view its actually cut off when the lens is edged, or the distortion exists only on the vitural blank.

I would classify your list as such (but these are debatable):

Gp wide (hard, but like Comfort)
gradal top (combined)
gt2 (combined)
brevety (combined)
summit ecp (soft, but combined in higher powers)
summit cd (combined)
picollo (hard)
hoya id (digital)
zeiss individual (digital)

Sharpstick

(digital with power management on both lens surfaces)

[Yeap]

yes.. current new lens mostly are combination of hard n soft. soft will be at the intermediate and the hard design will be pushed to the peripheral of ADD area. this is to provide a very comfortable wearing for Distance, inter and near..

[Darryl Meister]

I generally use an "ashtray" analogy to describe the differences between "hard" and "soft" progressive lens design philosophies...

Imagine a clear ashtray. For every diopter of addition power, a scoop of white sand must be dumped into this ashtray. This sand represents unwanted astigmatism and distortion.

Now, the progressive lens designer's problem is to distribute this sand in the most optimum way to provide useful distance, intermediate, and near vision.

The sand can be pushed to either side as much as possible to produce wide fields of clear vision. However, the piles of sand are extremely high in this case, resulting in significant blur and distortion in the periphery. This represents a "hard" design.

Alternatively, the sand can be spread over both sides of the ashtray to produce less blur and distortion in the periphery. However, the sand covers more of the ashtray in this case, resulting in significantly narrower fields of clear view. This represents a "soft" design.

That said, most modern progressive lens designs are neither strictly "hard" nor "soft." Instead, modern progressive lenses often seek to reach the best balance between both lens design philosophies.

You might also find the following articles on progressive lens design helpful: Progress in the Spectacle Correction of Presbyopia and Fundamentals of Progressive Lenses.

[sharpstick777]

I generally use an "ashtray" analogy to describe the differences between "hard" and "soft" progressive lens design philosophies...

Imagine a clear ashtray. For every diopter of addition power, a scoop of white sand must be dumped into this ashtray. This sand represents unwanted astigmatism and distortion.

The sand can be pushed to either side as much as possible to produce wide fields of clear vision. However, the piles of sand are extremely high in this case, resulting in significant blur and distortion in the periphery. This represents a "hard" design.

Alternatively, the sand can be spread over both sides of the ashtray to produce less blur and distortion in the periphery. However, the sand covers more of the ashtray in this case, resulting in significantly narrower fields of clear view. This represents a "soft" design.

Darrel,
Side question... isn't it theoretically possible to move this distortion father away from the field of view toward the outside of the lens (or the virtual lens) too? Instead of just "around"?

Sharpstick

[DragonLensmanWV]

WOW! That's a most eloquent analogy Darryl. I'll have to use it sometime.

One analogy I use when discussing ABBE with a customer is to have them imagine a crystal chandelier, then a glass chandelier. Then ask them which they would rather look through - the clear glass one or the glinty rainbowy crystal one.

[xiaowei]

WOW! That's a most eloquent analogy Darryl. I'll have to use it sometime.

One analogy I use when discussing ABBE with a customer is to have them imagine a crystal chandelier, then a glass chandelier. Then ask them which they would rather look through - the clear glass one or the glinty rainbowy crystal one.

This actually IS a good analogy, especially because most customers believe (and probably some dealers would prefer the customer to keep thinking that way....) that more expensive (higher index lens, crystal vs. glass) automatically meanes a "better" view!!!:D

[HarryChiling]

I generally use an "ashtray" analogy to describe the differences between "hard" and "soft" progressive lens design philosophies...

Imagine a clear ashtray. For every diopter of addition power, a scoop of white sand must be dumped into this ashtray. This sand represents unwanted astigmatism and distortion.

Now, the progressive lens designer's problem is to distribute this sand in the most optimum way to provide useful distance, intermediate, and near vision.

The sand can be pushed to either side as much as possible to produce wide fields of clear vision. However, the piles of sand are extremely high in this case, resulting in significant blur and distortion in the periphery. This represents a "hard" design.

Alternatively, the sand can be spread over both sides of the ashtray to produce less blur and distortion in the periphery. However, the sand covers more of the ashtray in this case, resulting in significantly narrower fields of clear view. This represents a "soft" design.

That said, most modern progressive lens designs are neither strictly "hard" nor "soft." Instead, modern progressive lenses often seek to reach the best balance between both lens design philosophies.

You might also find the following articles on progressive lens design helpful: Progress in the Spectacle Correction of Presbyopia and Fundamentals of Progressive Lenses.

So it was you that I got the sand box analogy from, I had a hunch. I have explained it this way for a little while now and the eureka on opticians faces is priceless, thanks this is th emost usefull explanation ever described of profressives.

[Darryl Meister]

isn't it theoretically possible to move this distortion father away from the field of view toward the outside of the lens (or the virtual lens) too? Instead of just "around"?

In my analogy, this really equates to the same thing. You can push the astigmatism farther out, thereby making the lens design "harder," but doing so will necessitate higher levels of unwanted astigmatism.

So it was you that I got the sand box analogy from, I had a hunch

It's entirely possible, Harry. In any case, it is a very effective analogy for explaining the optical limitations and design philosophies of progressive lenses.

[sharpstick777]

In my analogy, this really equates to the same thing. You can push the astigmatism farther out, thereby making the lens design "harder," but doing so will necessitate higher levels of unwanted astigmatism.

Darryl,
Is the unwanted astigmatism increased at a rate of 1:1 inversely to how far out you move out the distortion? or because net area increases with larger diameter is the rate reduced the farther out we go. (I know the term has caught on with everyone, but to me astigmatism can only happen to eyes not lenses).

The reason I ask is that if I had a virtual blank of 130mm would it be possible in theory to move much of the inherant distortions beyond the range of the view, thus enabling less distorted progressive (as far as the patient can see).

Thanks
Sharpstick

[HarryChiling]

The reason I ask is that if I had a virtual blank of 130mm would it be possible in theory to move much of the inherant distortions beyond the range of the view, thus enabling less distorted progressive (as far as the patient can see).

Thanks
Sharpstick

No.

[drk]

Sandbox: nicer analogy than "ashtray".

Of course, I still prefer my analogy: cat litter box...

[HarryChiling]

Of course, I still prefer my analogy: cat litter box...

That's a crappy analogy. :D

[JanMueller]

The ashtray thing is pretty well formulated. The former director of the "Höhere Fachschule für Augenoptik" (HFAK) in Cologne, Professor Josef Rainer first used this similarity. My grandfather and my father learned at the HFAK (me too...) and one evening when Zeiss brought their first Gradal I to the german opticians (they did at the HFAK) he uses this statement, and since then I hear this every day from my father. It' s one of the best things to explain the distortions to clients, because everyone understands... (And Zeiss related guys loves this, too:cheers:)