DoF may not exist...

Started 5 months ago | Discussions
NotASpeckOfCereal Senior Member • Posts: 2,075
Re: DoF may not exist...
1

moimoi wrote:

Short counter answer: DoF does exist so is the moon and the sun 🌞😎

More seriously, best to open a photography book and enjoy the art rather than the charts. Just my 2 cents of course.

Without agreeing or disagreeing, if someone DID want to talk about these things, this is sort of the place for it. Telling those folk that it's best to do something else is just a wee bit weird.

Not that I'm one of the eggheads here, but I would agree that this is the kind of knowledge that leads to engineering of better optics and cameras. Rather, already hasβ€”without it, we'd still be futzing around with gear that's a lot less effectual, as we did a century ago.

But do crack open that book and enjoy the corner-to-corner sharpness made by artists using the best of photographic gear.

Alternative Reply: there is no spoon.

Chris

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Erik Kaffehr
OP Erik Kaffehr Veteran Member • Posts: 6,309
The reason for this thread...

One reason is that DoF (Depth of Field) is a concept of acceptable sharpness. It is a very simple concept that had served photographers well for over hundred years.

At the same time, photographers knew that DoF was a simplification, based on human visions and expected viewing conditions.

Some of the basic assumption were:

  • Closest viewing distance would be around 25 cm or 10", that is based on normal human vision. 
  • Prints were not very large and larger pictures would be viewed at longer distance.

That led to a formulation where the acceptable blur was 1/1500-th of the diagonal of the negative. Using that figure, the acceptable blur circle for 24x36 mm is 43 mm/ 1500 -> 0.029 mm, this has been rounded to 0.030 mm.

Doing the same math 6x7 cm film, assuming a real frame size of 55x69 mm, the figure would be 88/1500 -> 0.06 mm.

0.030 and 0.060 mm were used for calculating DoF scales for 24x35 mm and 6x7 cm lenses.

Now, if we would look at nearest and most distant points of acceptable focus when using the DoF scales on the lens and printing at the same size, those points would be equally sharp.

But, I would assume that most photographers moving from 24x36 mm to 6x7 cm wanted sharper images.

One way of achieving that is to stop down more. So, shooting 67 cm we may use twice the f-numbers as indicated on the lens barrel.

But, stopping down increases blur, so at some point blur from diffraction exceeds the size of the geometric blur. Stopping down more does not gain more sharpness. Germans call it förderliche blende.

Jim Kassons curves are calculated from several hundred images, so it could be said that the curves say more than hundreds of images.

In a way, DoF tables served photographers well.

But, the digital era is a bit different. In the film era we did not print that large so often and at least I usually checked slides using a 15X loupe. That was not very convenient.

With digital, print sizes may have increased and we often view images on screens that are large compared to the 8"x10" prints we often had in the film era.

Also, we can zoom into images to great depth. That essentially means that DoF parameters based on film era print sizes need to be modified.

Best regards

Erik

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Greg7579
Greg7579 Forum Pro • Posts: 14,041
Re: The reason for this thread...

Erik Kaffehr wrote:

One reason is that DoF (Depth of Field) is a concept of acceptable sharpness. It is a very simple concept that had served photographers well for over hundred years.

Not anymore. That's the whole point. Photographers then were not seeing what we see now. Plus they were not shooting GFX and they were not doing post on powerful computers with these new fantastic monitors which are only getting better every year.

Erik, it is time. Fuji, it is time. Forget the math and CoC and do the work by shooting in a lab and in the wild and stating when the pixels start to lose it. Please.

Someone (Fuji) please do DOF tables for all of the GF lenses and please do not even mention CoC in them. Just do the tables and state the distances at all the apertures for each lens at each focal length of the zooms.  That's a lot of stuff, but easy to plug in on an app.

II don't need it because I have shot it so much.  But it would get the base-line right and stop these threads from popping up on this Board every day. 😁

At the same time, photographers knew that DoF was a simplification, based on human visions and expected viewing conditions.

Some of the basic assumption were:

  • Closest viewing distance would be around 25 cm or 10", that is based on normal human vision.
  • Prints were not very large and larger pictures would be viewed at longer distance.

That led to a formulation where the acceptable blur was 1/1500-th of the diagonal of the negative. Using that figure, the acceptable blur circle for 24x36 mm is 43 mm/ 1500 -> 0.029 mm, this has been rounded to 0.030 mm.

Doing the same math 6x7 cm film, assuming a real frame size of 55x69 mm, the figure would be 88/1500 -> 0.06 mm.

0.030 and 0.060 mm were used for calculating DoF scales for 24x35 mm and 6x7 cm lenses.

Now, if we would look at nearest and most distant points of acceptable focus when using the DoF scales on the lens and printing at the same size, those points would be equally sharp.

But, I would assume that most photographers moving from 24x36 mm to 6x7 cm wanted sharper images.

One way of achieving that is to stop down more. So, shooting 67 cm we may use twice the f-numbers as indicated on the lens barrel.

But, stopping down increases blur, so at some point blur from diffraction exceeds the size of the geometric blur. Stopping down more does not gain more sharpness. Germans call it förderliche blende.

Jim Kassons curves are calculated from several hundred images, so it could be said that the curves say more than hundreds of images.

In a way, DoF tables served photographers well.

But, the digital era is a bit different. In the film era we did not print that large so often and at least I usually checked slides using a 15X loupe. That was not very convenient.

With digital, print sizes may have increased and we often view images on screens that are large compared to the 8"x10" prints we often had in the film era.

Also, we can zoom into images to great depth. That essentially means that DoF parameters based on film era print sizes need to be modified.

Best regards

Erik

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JimKasson
MOD JimKasson Forum Pro • Posts: 36,158
Done and dusted
2

Greg7579 wrote:

Erik, it is time. Fuji, it is time. Forget the math and CoC and do the work by shooting in a lab and in the wild and stating when the pixels start to lose it. Please.

I did that a year ago, at your request. You have ignored my recommendations. Here's a data point: with a 45 mm lens on a GFX 100x at f/5.6, focused at 100 meters, the threshold of critical focus at 1:1 is at 50 meters. Critical focus in that case extends -- just barely -- all the way to infinity.

I asked to you check and see if you agree. I gave you a test to perform that will take you half an hour that should be dispositive. You ahve not done it.

Someone (Fuji) please do DOF tables for all of the GF lenses and please do not even mention CoC in them. Just do the tables and state the distances at all the apertures for each lens at each focal length of the zooms.

I can do that once you verify that what you think is the threshold of critical focus is what I think the threshold of critical focus is.

That's a lot of stuff, but easy to plug in on an app.

Once you verify my findings -- which I've tested in the field -- I can tell you how to set up most any DOF calculator to do what you're asking.

You asked -- a long time ago, not just today. I answered. I did a fair amount of work to verify my answer (which, by the way, works for the a7RIV, too). I asked you to see if you agree with my answer. You haven't done that. The ball is in your court.

Jim

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JimKasson
MOD JimKasson Forum Pro • Posts: 36,158
Re: DoF may not exist...

Erik Kaffehr wrote:

Now, we can see that f/2.8 yields acceptable sharpness from 206 to 208 cm, while f/11 yields acceptable sharpness from 2.035 to 2.08 m.But, maximum sharpness is reduced from 3500 cy/PH to around 1800 cy/PH when stopping down. That is due to diffraction. So, we gained depth of field while giving up on maximal sharpness.

With a CoC of 7 um, we get something similar from geometric optics:

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DMillier Forum Pro • Posts: 23,017
Re: The reason for this thread...

If you don't accept DOF tables, just tighten the CoC value until tables calculated from it match your eyeballing of the images.

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JimKasson
MOD JimKasson Forum Pro • Posts: 36,158
Re: The reason for this thread...

DMillier wrote:

If you don't accept DOF tables, just tighten the CoC value until tables calculated from it match your eyeballing of the images.

https://blog.kasson.com/the-last-word/choosing-coc-for-precision-photography-in-practice/

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NotASpeckOfCereal Senior Member • Posts: 2,075
Re: The reason for this thread...
1

JimKasson wrote:

DMillier wrote:

If you don't accept DOF tables, just tighten the CoC value until tables calculated from it match your eyeballing of the images.

https://blog.kasson.com/the-last-word/choosing-coc-for-precision-photography-in-practice/

Heck, I just press the DOF Preview button.

<ducks from show thrown across the room>

Chris

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highdesertmesa
highdesertmesa Contributing Member • Posts: 811
Re: The reason for this thread...

NotASpeckOfCereal wrote:

JimKasson wrote:

DMillier wrote:

If you don't accept DOF tables, just tighten the CoC value until tables calculated from it match your eyeballing of the images.

https://blog.kasson.com/the-last-word/choosing-coc-for-precision-photography-in-practice/

Heck, I just press the DOF Preview button.

<ducks from show thrown across the room>

Chris

Which is one reason the GFX 100S (and upcoming 50S II) not having the EVF from the GFX 100 is unfortunate.

Greg7579
Greg7579 Forum Pro • Posts: 14,041
Re: Done and dusted

JimKasson wrote:

Greg7579 wrote:

Erik, it is time. Fuji, it is time. Forget the math and CoC and do the work by shooting in a lab and in the wild and stating when the pixels start to lose it. Please.

I did that a year ago, at your request.

Not really.  You took a few snapshots at various apertures and posted the pictures.

It was interesting and you do great work, but I take shots like that all the time and view the results so I'm not sure what that was really telling me that I haven't already seen.

You have ignored my recommendations.

I never ignore you.  That would be like ignoring Teresa and it only leads to sadness and despair in my day.

Here's a data point: with a 45 mm lens on a GFX 100x at f/5.6, focused at 100 meters, the threshold of critical focus at 1:1 is at 50 meters. Critical focus in that case extends -- just barely -- all the way to infinity.

I asked to you check and see if you agree. I gave you a test to perform that will take you half an hour that should be dispositive. You ahve not done it.

I'm not interested in conducting tests for you Jim. You know I luv ya Man but it is starting to get irritating.   You do the testing.  You are determined to get me to shoot a 50 meter target with one GF lens and then apply a specific CoC that you have devised and that you know will work for that shot and that is supposed to somehow renew my faith in the Holy DOF tables and the unusable (for most normal people) fudge-factor scientists call  CoC.

Then somehow I will become convinced that the tables are now sound when I already know they are not.  How do I know?  Because I shoot GFX almost every day of my life and I see DOF like Rembrandt saw half-lit faces.  So trust me.  I know  You just gotta have some trust in me Brother.

We're a team Jim.  I shoot in the wild.  You shoot, test and teach.  I'm listening and learning but that does not mean we will agree on every GFX tidbit.  Because that is all this is.  A tidbit.

Someone (Fuji) please do DOF tables for all of the GF lenses and please do not even mention CoC in them. Just do the tables and state the distances at all the apertures for each lens at each focal length of the zooms.

I can do that once you verify that what you think is the threshold of critical focus is what I think the threshold of critical focus is.

That's a lot of stuff, but easy to plug in on an app.

Once you verify my findings -- which I've tested in the field -- I can tell you how to set up most any DOF calculator to do what you're asking.

You asked -- a long time ago, not just today. I answered. I did a fair amount of work to verify my answer (which, by the way, works for the a7RIV, too). I asked you to see if you agree with my answer. You haven't done that. The ball is in your court.

If it works for the alphasevenarefour then I am suspicious because that camera is a smaller format that we used to call Full-Frame that has a lot more DOF than the GFX.  😁

Jim

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JimKasson
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Horse, water, and drinking

Greg7579 wrote:

JimKasson wrote:

Greg7579 wrote:

Erik, it is time. Fuji, it is time. Forget the math and CoC and do the work by shooting in a lab and in the wild and stating when the pixels start to lose it. Please.

I did that a year ago, at your request.

Not really. You took a few snapshots at various apertures and posted the pictures.

It was interesting and you do great work, but I take shots like that all the time and view the results so I'm not sure what that was really telling me that I haven't already seen.

That's not what I'm talking about. You asked then, as you did now, for specific ways to use the DOF calculators that were appropriate for the kind of extreme pixel-peeping that you do. I told you that, with the GFX 100, that a CoC of about the pixel pitch would work. That's a 4 um CoC diameter. I gave you a test to perform to see if my recommendations were right for your eyes.

You said you'd perform the test.

You have not.

Horse led to water. Not drinking.

Jim

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JimKasson
MOD JimKasson Forum Pro • Posts: 36,158
Re: Done and dusted

Greg7579 wrote:

JimKasson wrote:

You asked -- a long time ago, not just today. I answered. I did a fair amount of work to verify my answer (which, by the way, works for the a7RIV, too). I asked you to see if you agree with my answer. You haven't done that. The ball is in your court.

If it works for the alphasevenarefour then I am suspicious because that camera is a smaller format that we used to call Full-Frame that has a lot more DOF than the GFX. 😁

Greg, you are quick to disparage the conclusions about the GFX of those that don't shoot the GFX. Yet, you have the temerity to opine with superlative certainty about the a7RIV, which I believe you have never used. Have you used the a7RIV in secret?

I have both GFX 100x cameras and an a7RIV. When you do the kind of examination of the image at 1:1 that you're talking about, the size of the sensor doesn't matter. In both the case of the a7RIV and thew GFX 100x, the vast majority of the pixels in the image will be off the screen, and won't influence what you're seeing. What will influence what you're seeing as to sharpness vs focal plane distance is the pitch of the sensor -- which is the same for all three cameras, the size of the microlenses -- which is the same for all three cameras, the lens, the aperture, the subject distance, and where the lens is focused.

Take the same lens, set it to an f-stop, focus it at a certain distance, aim it at a subject, take the picture, develop it, and pixel peep at 100% magnification. You'll see the same sharpness vs distance for both the a7RIV and the GFX 100x. So the same CoC diameter is appropriate for prior knowledge of the visual DOF.

Why is this so hard to understand?

Jim

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JimKasson
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Change of mind?

Greg7579 wrote:

I'm not interested in conducting tests for you Jim.

You've changed your mind so quickly from what you said here ?

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Greg7579
Greg7579 Forum Pro • Posts: 14,041
Re: Horse, water, and drinking
1

JimKasson wrote:

Greg7579 wrote:

JimKasson wrote:

Greg7579 wrote:

Erik, it is time. Fuji, it is time. Forget the math and CoC and do the work by shooting in a lab and in the wild and stating when the pixels start to lose it. Please.

I did that a year ago, at your request.

Not really. You took a few snapshots at various apertures and posted the pictures.

It was interesting and you do great work, but I take shots like that all the time and view the results so I'm not sure what that was really telling me that I haven't already seen.

That's not what I'm talking about. You asked then, as you did now, for specific ways to use the DOF calculators that were appropriate for the kind of extreme pixel-peeping that you do. I told you that, with the GFX 100, that a CoC of about the pixel pitch would work. That's a 4 um CoC diameter. I gave you a test to perform to see if my recommendations were right for your eyes.

You said you'd perform the test.

You have not.

Horse led to water. Not drinking.

Jim

OK.  I'll shoot it when I get back.

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JimKasson
MOD JimKasson Forum Pro • Posts: 36,158
Re: Horse, water, and drinking

Greg7579 wrote:

JimKasson wrote:

Greg7579 wrote:

JimKasson wrote:

Greg7579 wrote:

Erik, it is time. Fuji, it is time. Forget the math and CoC and do the work by shooting in a lab and in the wild and stating when the pixels start to lose it. Please.

I did that a year ago, at your request.

Not really. You took a few snapshots at various apertures and posted the pictures.

It was interesting and you do great work, but I take shots like that all the time and view the results so I'm not sure what that was really telling me that I haven't already seen.

That's not what I'm talking about. You asked then, as you did now, for specific ways to use the DOF calculators that were appropriate for the kind of extreme pixel-peeping that you do. I told you that, with the GFX 100, that a CoC of about the pixel pitch would work. That's a 4 um CoC diameter. I gave you a test to perform to see if my recommendations were right for your eyes.

You said you'd perform the test.

You have not.

Horse led to water. Not drinking.

Jim

OK. I'll shoot it when I get back.

Thank you.

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Greg7579
Greg7579 Forum Pro • Posts: 14,041
Re: Done and dusted

JimKasson wrote:

Greg7579 wrote:

JimKasson wrote:

You asked -- a long time ago, not just today. I answered. I did a fair amount of work to verify my answer (which, by the way, works for the a7RIV, too). I asked you to see if you agree with my answer. You haven't done that. The ball is in your court.

If it works for the alphasevenarefour then I am suspicious because that camera is a smaller format that we used to call Full-Frame that has a lot more DOF than the GFX. 😁

Greg, you are quick to disparage the conclusions about the GFX of those that don't shoot the GFX. Yet, you have the temerity to opine with superlative certainty about the a7RIV, which I believe you have never used. Have you used the a7RIV in secret?

I have both GFX 100x cameras and an a7RIV. When you do the kind of examination of the image at 1:1 that you're talking about, the size of the sensor doesn't matter. In both the case of the a7RIV and thew GFX 100x, the vast majority of the pixels in the image will be off the screen, and won't influence what you're seeing. What will influence what you're seeing as to sharpness vs focal plane distance is the pitch of the sensor -- which is the same for all three cameras, the size of the microlenses -- which is the same for all three cameras, the lens, the aperture, the subject distance, and where the lens is focused.

Take the same lens, set it to an f-stop, focus it at a certain distance, aim it at a subject, take the picture, develop it, and pixel peep at 100% magnification. You'll see the same sharpness vs distance for both the a7RIV and the GFX 100x. So the same CoC diameter is appropriate for prior knowledge of the visual DOF.

Why is this so hard to understand?

Jim

You are right about that alphasevenarefour bit. I haven't shot it.  I have shot the Q2 and Canon FF DSLRs for years.  And of coursecI shot Fuji X a bazillion times with every lens they made but the 200.

t it.  --
Greg Johnson, San Antonio, Texas
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JimKasson
MOD JimKasson Forum Pro • Posts: 36,158
Re: Done and dusted

Greg7579 wrote:

JimKasson wrote:

Greg7579 wrote:

JimKasson wrote:

You asked -- a long time ago, not just today. I answered. I did a fair amount of work to verify my answer (which, by the way, works for the a7RIV, too). I asked you to see if you agree with my answer. You haven't done that. The ball is in your court.

If it works for the alphasevenarefour then I am suspicious because that camera is a smaller format that we used to call Full-Frame that has a lot more DOF than the GFX. 😁

Greg, you are quick to disparage the conclusions about the GFX of those that don't shoot the GFX. Yet, you have the temerity to opine with superlative certainty about the a7RIV, which I believe you have never used. Have you used the a7RIV in secret?

I have both GFX 100x cameras and an a7RIV. When you do the kind of examination of the image at 1:1 that you're talking about, the size of the sensor doesn't matter. In both the case of the a7RIV and thew GFX 100x, the vast majority of the pixels in the image will be off the screen, and won't influence what you're seeing. What will influence what you're seeing as to sharpness vs focal plane distance is the pitch of the sensor -- which is the same for all three cameras, the size of the microlenses -- which is the same for all three cameras, the lens, the aperture, the subject distance, and where the lens is focused.

Take the same lens, set it to an f-stop, focus it at a certain distance, aim it at a subject, take the picture, develop it, and pixel peep at 100% magnification. You'll see the same sharpness vs distance for both the a7RIV and the GFX 100x. So the same CoC diameter is appropriate for prior knowledge of the visual DOF.

Why is this so hard to understand?

Jim

You are right about that alphasevenarefour bit. I haven't shot it. I have shot the Q2 and Canon FF DSLRs for years. And of coursecI shot Fuji X a bazillion times with every lens they made but the 200.

None of those cameras have 3.76 um pitch, right?

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Erik Kaffehr
OP Erik Kaffehr Veteran Member • Posts: 6,309
Re: Done and dusted

JimKasson wrote:

Greg7579 wrote:

JimKasson wrote:

Greg7579 wrote:

JimKasson wrote:

You asked -- a long time ago, not just today. I answered. I did a fair amount of work to verify my answer (which, by the way, works for the a7RIV, too). I asked you to see if you agree with my answer. You haven't done that. The ball is in your court.

If it works for the alphasevenarefour then I am suspicious because that camera is a smaller format that we used to call Full-Frame that has a lot more DOF than the GFX. 😁

Greg, you are quick to disparage the conclusions about the GFX of those that don't shoot the GFX. Yet, you have the temerity to opine with superlative certainty about the a7RIV, which I believe you have never used. Have you used the a7RIV in secret?

I have both GFX 100x cameras and an a7RIV. When you do the kind of examination of the image at 1:1 that you're talking about, the size of the sensor doesn't matter. In both the case of the a7RIV and thew GFX 100x, the vast majority of the pixels in the image will be off the screen, and won't influence what you're seeing. What will influence what you're seeing as to sharpness vs focal plane distance is the pitch of the sensor -- which is the same for all three cameras, the size of the microlenses -- which is the same for all three cameras, the lens, the aperture, the subject distance, and where the lens is focused.

Take the same lens, set it to an f-stop, focus it at a certain distance, aim it at a subject, take the picture, develop it, and pixel peep at 100% magnification. You'll see the same sharpness vs distance for both the a7RIV and the GFX 100x. So the same CoC diameter is appropriate for prior knowledge of the visual DOF.

Why is this so hard to understand?

Jim

You are right about that alphasevenarefour bit. I haven't shot it. I have shot the Q2 and Canon FF DSLRs for years. And of coursecI shot Fuji X a bazillion times with every lens they made but the 200.

None of those cameras have 3.76 um pitch, right?

The long delayed annual research paper from SloofLirpa may bring some clarity on the issues involved...

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Erik Kaffehr
OP Erik Kaffehr Veteran Member • Posts: 6,309
The missing experiment

Hi,

I tried to do the experiment Jim was suggesting. My objects were at 130, 100 and 29 m distant. Used Sony A7rIV with Sigma 45/2.8 Contemporary I. Focus is intended to be at 130 m.

Sony A7rIV, 45 mm f/4 - f/22 low sharpening in Lightroom.

Best regards

Erik

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Greg7579
Greg7579 Forum Pro • Posts: 14,041
Re: Change of mind?

JimKasson wrote:

Greg7579 wrote:

I'm not interested in conducting tests for you Jim.

You've changed your mind so quickly from what you said here ?

I read your pleas and I like you and respect you and learn from you so I decide to do it.  Then I get people warning me not to.  They say, "Greg just shoot.  Don't get sucked into their testing world or they will eat you alive."  Let them do the tests.  All good.  You just shoot and tell us what you see and what your experiences are.  We can weigh it all on our own.  Testing and shooting.  All good.

Anyway,  It's no big deal.  Really.

I would leave it alone, but you guys never will.  There will be 20 more testing threads on DOF all because I said what I know I see.

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Leica Q2 Fujifilm GFX 50R Fujifilm GFX 100 Fujifilm GF 32-64mm F4 Fujifilm 120mm F4 Macro +8 more
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