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04-21-2015, 10:49 AM - 3 Likes   #3991
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I took Charlotte to her dance lesson and then zipped over to Poitiers' botanical garden to test further the Will Wetzlar Magninon 100/2.8 projector lens in its new heliocoid base. Again shot "wide open" on K-5. No aperture incorporated (yet) in this combo. xpost





04-21-2015, 11:24 AM - 1 Like   #3992
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QuoteOriginally posted by Nicolas06 Quote
First the source is dof master, you can try for yourself: Online Depth of Field Calculator or do a search on google for an alternate tool.

Second is you read the table you provided you can check the number for yourself:

From your table focus at 2m and changing the apperture from f/2 ot f/8:
at f/2 the total deph of field is 2.21-1.83 = 0.38m
at f/4 the total deph of field is 2.48-1.68 = 0.8m (x2 rougly of f/2)
at f/8 the total deph of field is 3.28-1.45 = 1.83m (x2 rougly of f/4).

It would not work at f/16 in this case because for this lense this would be you already focus near infinite.

You could try again say focussing at 0.5m:
at f/2 the total deph of field is 0.510-0.491 = 0.019
at f/4 the total deph of field is 0.519-0.482 = 0.37 (x2 rougly of f/2)
at f/8 the total deph of field is 0.541-0.466 =0.075 (x2 rougly of f/4).

Third if you check the formula of deph of field, you would see that focal length has much more impact on deph of field than apperture.

Using one of the online similutor and change the focal length. You would see that at 135mm instead of 35mm for the same focussing distance the deph of field is divived by 16 because the focal length is multiplied by 4 (it is the square).

You would see also the focussing distance is also very important and change dramatically the deph of field.

This is why guys doing macro for example never have enough deph of field and do focus staking and also why even wide open with wide angle everything is almost always in focus except for proxy shoots. This is why when you shoot a bird with a very long tele there no much deph of field even at f/8 or f/11...

Anyway, look at the picture I provided, like it or not, the background is blured and this is f/11 and an APSC. I choosed one on purpose with boats behind to show the amount of blur. Most of the shoots of that day, there was only the sky behind with a few clounds so very creamy and soft background.
Do you realise that every lens has a different design so your online depth of field calculator is completely useless?

IMO NO!

Here there are some tables I've found on the fly:

Super Tak:



Olympus 50 mm



This is interesting because it compares a Canon EF 50 mm f`1.4 with a 1.8...at the same aperture and focusing distance the DOF is different:





Now, enough for mathematics and wacky bokeh definitions and let's the pics do the talking.

Pentax LX, M 50 mm f1.4, Portra 160:








Last edited by Cuthbert; 04-21-2015 at 11:47 AM.
04-21-2015, 12:08 PM   #3993
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QuoteOriginally posted by Cuthbert Quote
Now, enough for mathematics and wacky bokeh definitions and let's the pics do the talking.
If you take care to read your table carefully you see that the number are the same for you Canon f/1.8 and f/1.4, You can argue on a 1% difference but this is not significant. And yeah, different sensor and different units will give different numbers but that is to be expected. The rules remain. Up to my knowledge I never seen a manufacturer saying, this is a lense with special shallow deph of field design. The f/2.8 setting of this one is like the f/5.6 design on a classical one. Special for portrairure and shallow deph of field work! The difference you speak of are marginal.

Anyway, the photo was speaking for itself, you can have shallow deph of field even at f/8 or f/11. Proof by practice.
04-21-2015, 12:48 PM - 1 Like   #3994
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I think this thread deserves more bokeh and less bla bla...

K2DMD, K50 mm f1.4 and Neopan:





OT, I think the Dodo used to be 99% equal to a pigeon from a genetic point of view, nevertheless it wasn't a pigeon!

04-21-2015, 01:10 PM - 4 Likes   #3995
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an oldie from a few years ago (might be a re-post):
A35-70/4
04-21-2015, 03:40 PM   #3996
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QuoteOriginally posted by Cuthbert Quote
OT, I think the Dodo used to be 99% equal to a pigeon from a genetic point of view, nevertheless it wasn't a pigeon!
Profound hypothesis to remember, could serve as key argument for next discussion! I'll let you perform the DNA analysis to confirm it.
04-21-2015, 03:50 PM - 1 Like   #3997
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QuoteOriginally posted by Cuthbert Quote
Do you realise that every lens has a different design so your online depth of field calculator is completely useless?

IMO NO!
Dude... the laws of physics don't change because someone designed a lens differently. If the DoF is different (and it won't be by much) it's because someone labeled the lens at a different focal length than what it actually is.

Usually when you see the difference is because one brand's f/1.7 is actually a 1.75 while the next's 1.7 is actually 1.8 while the next is 1.65, etc etc

EDIT: Oh yea, bokeh photos...

Auto Sears 28mm, f/2.8 wide open...




Last edited by Sagitta; 04-21-2015 at 03:55 PM.
04-21-2015, 03:57 PM   #3998
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QuoteOriginally posted by Sagitta Quote
Dude... the laws of physics don't change because someone designed a lens differently. If the DoF is different (and it won't be by much) it's because someone labeled the lens at a different focal length than what it actually is.
Thank you very much, I'm a mechanical engineer, I design cars and I know nothing about laws of physics, it's fine to find knowledgeable like you guys can can lecture me on the topic "it doesn't matter the design of a lens, number of elements etc... they all have the same DOF."...I wonder where you got your degrees, if you had any.

However, the bokeh pic is for you!

04-21-2015, 05:39 PM - 1 Like   #3999
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QuoteOriginally posted by Cuthbert Quote
Thank you very much, I'm a mechanical engineer, I design cars and I know nothing about laws of physics, it's fine to find knowledgeable like you guys can can lecture me on the topic "it doesn't matter the design of a lens, number of elements etc... they all have the same DOF."...I wonder where you got your degrees, if you had any.

However, the bokeh pic is for you!
A 135mm lens is a 135mm lens is a 135mm lens. It is designed to project a set value of magnification on a subject, regardless of how its built. If it projects a wider or lesser amount of magnification it is no longer a 135mm lens.

This is why you can have a 35mm ltd which is tiny and weighs next to nothing, or a Samyang 35mm which is built like a tank and probably weighs almost as much. Just because both are made differently, they're still both 35mm lenses because they both project a certain specific amount of magnification upon a sensor/bit of film/whatever. If they magnified more, they would be a longer focal length. If they magnified less, they would be a shorter focal length. This is Photography 101 stuff. The depth of field and all that stuff carries over due to that 35mm length and will not vary. It won't vary because if the lens is built exactly to specs and is exactly 35mm (or 135mm, or whatever) the depth of field can then be predicted as a result because of the math involved.

Of course this isn't the case, because lenses vary in focal length depending on design. That Pentax 50mm may actually be a 49mm. The Canon may be a 51.5mm. The Nikon could be a 49.5mm. All three will be stamped as a 50mm of course because thats what they (mostly) are to the casual photographer.

That's partly where the variance comes into play. The other comes when they measure the aperture values. Pentax's lens could actually be f/1.65, Canon's f/1.75, and Nikon's f/1.775. All three will stamp them as f/1.7 - again - for the ease of labeling and the fact that the difference isn't enough to quibble about.

The basic math involved isn't going to change. If you could increase or decrease depth of field by fiddling with the optics in a lens, it would have been done ages ago and would have been advertised as such. Of course this never happened because when you start fiddling with the optics you are either going to change the focal length or the aperture qualities of the lens or both.

Depth of field dependence on focal length is a constant. Its the fact that lenses may be slightly longer or shorter and have differently measured aperture values compared to whats stamped on them that changes things up and muddies the figures.

This is also why the depth of field is going to stay the same no matter what lens you're using.

A 28mm at f/4 will have the same DoF as a 50mm at f/4 as a 135mm at f/4 as a 300mm at f/4 (provided of course the lenses are actually the focal length advertised and the aperture values are measured to spec). The only difference is going to be how close or far from the subject you need to be to have it the same size in-frame for the camera.
04-21-2015, 10:55 PM - 1 Like   #4000
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QuoteOriginally posted by Sagitta Quote
A 28mm at f/4 will have the same DoF as a 50mm at f/4 as a 135mm at f/4 as a 300mm at f/4 (provided of course the lenses are actually the focal length advertised and the aperture values are measured to spec). The only difference is going to be how close or far from the subject you need to be to have it the same size in-frame for the camera.
This one is true if you keep the same framing. So the subject distance of the 50mm would have to be 50/28=1.78 more and for a 300mm vs 28, subject distance would have to be 10.7 time more.

Even in this case while the deph of field (the range in focus) would remain the same, the perspective rendering (distorsion, compression) would be widely different as would be the amount of background blur.

If the framing is not kept, for example you focus your DA300 to 10m for a bird and your to 10m FA28 to a house on a landscape, the deph of field will be dramatically different.

In the end the issue stay the same for a given subject/usage/framing the only thing you can change is apperture, that true but the range of what you can get is limited. For a macro shoot, a tight portrait or birding/wildlife, it might be difficult to impossible to have everything perfectly in focus on a APSC or FF while on a landscape taken with a wide angle lens it might be difficult to impossible to have a specific subject in focus and the rest out of focus.
04-22-2015, 11:30 AM - 1 Like   #4001
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18-135 at 135 5,6 PP on phone
04-22-2015, 12:02 PM - 1 Like   #4002
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K 55 f2, all wide open (xposted)



This is one effect I'm usually pleased when it happens, when the bokeh makes the picture look more like a painting...

04-22-2015, 04:26 PM   #4003
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QuoteOriginally posted by ChristianRock Quote
K 55 f2, all wide open (xposted)



This is one effect I'm usually pleased when it happens, when the bokeh makes the picture look more like a painting...

The K55 f2.0 is a very good lens:



04-23-2015, 04:38 AM - 3 Likes   #4004
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M*300/4 and Selsey Beach

For a 300mm this has surprisingly nice bokeh.

04-23-2015, 12:55 PM - 1 Like   #4005
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K35/2

Took a wander about in the glorious spring sunshine today to have a play with this fine piece of Pentax craftmanship before I give it to my daughter for her birthday.
If I didn't have the A version, I'd be buying her something else, what a great lens.
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