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09-08-2011, 10:30 AM   #1
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Trying to avoid LBA

Was wondering is someone can point me in the right direction, Searching produced way more results than I can read thru. I know what the numbers mean but given a set focal range what determines if it is a 1.4 or 2.8 even 1.9 or 1.7 When buying why choose one over the other and not just opt for the 1.4? Am I missing something obviously budget has a lot to do with it from a buyer's perspective Or maybe I am not understanding it as well as I thought I did. I guess if the optical quality and price was the same kind of scenerio

JJ

09-08-2011, 10:55 AM   #2
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From Wiki the explanation of Aperture (f stop)


QuoteQuote:
the ratio of focal length to effective aperture diameter. A lens typically has a set of marked "f-stops" that the f-number can be set to. A lower f-number denotes a greater aperture opening which allows more light to reach the film or image sensor. The photography term "one f-stop" refers to a factor of √2 (approx. 1.41) change in f-number, which in turn corresponds to a factor of 2 change in light intensity.
As for why buy which a number of factors come into play. Certainly all other things being equal the 1.4 lens would be the better lens, but all other things are rarely equal. Bokeh (or ho out of focus areas look) is determined in a large part by the number of aperture blades, combined with he shape they would form (from a smooth round circle to a pentagon look for instance)
Also there are the number of elements and quality of glass along with build of the body (ie all metal, WR) what type of coating all come into play.
there is also the elusive idea of a lens having "pixie dust" an unquantifiable quality that makes it very desirable - think the FA limiteds.

the great hing with Pentax of course is given the huge number of affordable 50 mm lenses out there from Pentax and others you can experiment with a lot of these differences for relatively little money (coated and undercoated Takumars, f1.4,f1.7,f1.8,f1.9 F2.0 are all easily available speeds in either 50 or 55 in the old lenses. F1.2 will be a lot harder to come by (the a 50 1.2) which still has sporadic production runs and costs a bomb)
then there are the AF models. Macro models. Russian lenses, german lenses ...... well you get the idea. There are members here who have more than 50 50mm lenses
Personally I only have 6 or 7 all full manual models so i'm just a rank amateur compared to say digitalis or rio rico

The best advise i think i can give on LBA is try out focal lengths (if possible) on older more affordable lenses like the tak 55 1.8 or the tak 50 1.4 or an m 50 1.7 (I have all of the above and they each have there own look and feel)
09-08-2011, 11:05 AM   #3
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I think what you're asking is related to minimum aperture.
Basically, as a baseline, f/1 means that the front element of the lens is at minimum as large all of the rest of the elements in the lens, and that corresponds to the same amount of light that goes into the front element makes it to the back element. Now, if you use the aperture to go down to f/2, it will let 1/4 of the light in that it did at f/1. What are large apertures useful for? Shallow Depth of Field and getting shots in lower light settings.

When you buy a lens, as far as I understand it, the minimum aperture states effectively the most light that can be let through the lens. You can stop down the lens with the aperture to let less light through which improves depth of field, and up to a point, sharpness.

Aperture - Wikipedia, the free encyclopedia has more general information about aperture. I'm sure that there's a lot of useful utilities on here as well as to the relationship between aperture and light.

Also, knowledge is a dangerous thing - when I want to avoid LBA, I need to stay away from these forums.
09-08-2011, 11:10 AM   #4
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QuoteOriginally posted by icywindow Quote

Also, knowledge is a dangerous thing - when I want to avoid LBA, I need to stay away from these forums.
This.
This.
I hate this place.

09-08-2011, 11:16 AM   #5
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Eddie,
Great post, and no I really dont plan on amassing the numbers of digitalis or Rico unless I want to be a bachelor again but I was just trying to do apples to apples if possible and if Pentax offered three different 50mm (example only) I guess from my perspective I would opt for the lowest F# I'm just trying to stay with a few manufactures dont want to even think about the German or Russians.

Icy,
Yeah but avoiding these forums would throw my whole day off

JJ
09-08-2011, 11:31 AM   #6
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I think what you are asking is, why should I get say an f1.8 lens when I can get an f1.4, or an f2.8 versus an f1.8, yada yada yada. To me there are several factors, the first being cost. Faster lenses (wider aperture) usually cost more. Size and weight factor in to it too as faster lenses can be bigger and heavier than others. The shallow DoF on fast bright lenses can be very useful for photography but also can be very difficult to achieve a good focus with. Then, too, some lenses in this general area of discussion are just better than others. Read reviews on them and this comes out. I have a few f1.4 lenses and quite a few f2.8 lenses (some in between too). For my purposes the f1.4 lenses are special purpose ones (a 50mm and an 85mm), whereas the f2.8 ones are more general purpose. Does that help?
09-08-2011, 11:36 AM   #7
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If you start from the "need" end, it's easier to narrow down to a workable set of lenses. Defining what you really need is hard, but also instructive. If you can't think of any great reasons why you need a lens, why are you going to buy it? I don't stick to that absolutely, but above a certain price, I really have to have a purpose for a lens.
09-08-2011, 11:47 AM   #8
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QuoteOriginally posted by blackcloudbrew Quote
I think what you are asking is, why should I get say an f1.8 lens when I can get an f1.4, or an f2.8 versus an f1.8, yada yada yada. To me there are several factors, the first being cost. Faster lenses (wider aperture) usually cost more. Size and weight factor in to it too as faster lenses can be bigger and heavier than others. The shallow DoF on fast bright lenses can be very useful for photography but also can be very difficult to achieve a good focus with. Then, too, some lenses in this general area of discussion are just better than others. Read reviews on them and this comes out. I have a few f1.4 lenses and quite a few f2.8 lenses (some in between too). For my purposes the f1.4 lenses are special purpose ones (a 50mm and an 85mm), whereas the f2.8 ones are more general purpose. Does that help?
That is pretty much it in a nutshell that and Just wondered why some of the odd number like 1.7 and 1.9
QuoteOriginally posted by Just1MoreDave Quote
If you start from the "need" end, it's easier to narrow down to a workable set of lenses. Defining what you really need is hard, but also instructive. If you can't think of any great reasons why you need a lens, why are you going to buy it? I don't stick to that absolutely, but above a certain price, I really have to have a purpose for a lens.
Oh I am sure there will be a few want over need choices in my future but I agree for now it is a need situation.

JJ

09-08-2011, 12:33 PM - 1 Like   #9
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Many issues here. Why those odd numbers like f/1.7? Because that's how the lens was built. Why f/1.9? Because the number looks faster than f/2! (Yeah, lensmakers play marketing tricks too.) Why fast lenses? Because they're often better; the fastest are often the lensmakers' signature products. Why slow lenses? Because they may be quite sharp and nifty, and they're usually cheaper. Older glass, too. The average cost of my ~210 non-AF lenses is US$20 each. We own a rug that's worth more than I ever spent on photo gear. Poverty or divorce aren't necessary.

How to figure what's needed? My stock answers are to ask yourself questions: What do I want to do that I can't do with what I have? Where do I want to go, what will get me there, and how much do I want to spend to be happy? And of course, how much storage space do I have?

Or, take a multi-stage approach:

1) Coverage. My Tamron 10-24, DA18-250, and Sigma 170-500 cover a vast range.
2) Specialties. Fisheye, macro, mirror; costly fast long teles for sports+wildlife, etc.
3) Speed. Get the fastest lenses you can find+afford at your critical focal lengths.
4) Character (flaws). Get slow cheap old lenses that just render images differently.

Think of lenses as windows on the world; each makes you see differently. Think of lenses as artists' brushes; not all painting is done with a spatula. Think of lenses as spices; those with character (flaws) each have their own special flavour. Think of lenses as weapons; some of mine can easily crush a Chihuahua dog or a raccoon. Think of lenses as chess pieces; mate!

Last edited by RioRico; 09-08-2011 at 01:32 PM.
09-08-2011, 12:36 PM   #10
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QuoteOriginally posted by RioRico Quote

Think of lenses as windows on the world; each makes you see differently. Think of lenses as artists' brushes; not all painting is done with a spatula. Think of lenses as spices; those with character (flaws) each have their own special flavour. Think of lenses as weapons; some of mine can easily crush a Chihuahua dog or a raccoon. Think of lenses as chess pieces; mate!
Spoken like a true LB Addict.
^^
09-08-2011, 01:15 PM   #11
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Must buy...just one more lens!
09-08-2011, 01:22 PM   #12
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QuoteOriginally posted by blackcloudbrew Quote
Must buy...just one more lens!
So if you buy one while waiting on another one to ship does that fall within the realm of self control? Cause technically you have only been charged for one??

JJ
09-08-2011, 01:43 PM   #13
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QuoteOriginally posted by RickyFromVegas Quote
Spoken like a true LB Addict.
As distinct from the phonies? OK, all you LBA fakers out there, raise your tripods!

QuoteOriginally posted by jerryleejr Quote
So if you buy one while waiting on another one to ship does that fall within the realm of self control? Cause technically you have only been charged for one??
Lubarsky's Law of Cybernetic Entomology: There's always one more bug.
RioRico's Law of Optical Opportunism: There's always one more lens.

OR: I am RioRico of Borg. Your budget will be assimilated. Resistance is futile.

Which leads to:

I am Flatulus of Borg. Resistance is futile. Pull my finger.
I am Dyslexic of Borg. Fustence is retile. Your ass will be laminated.
I am Homer of Borg. Resistance is futile. You will be... oooh, DONUTS!!!
09-08-2011, 03:00 PM   #14
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If you are trying to avoid LBA don't post about it in here. Some very talented folks from here will maake you suffer from VERY severe case of LBA, and later CBA and later just I want it all BA...

Resistance is futile indeed!

Advice from me? Start saving, you'll need every penny!
09-08-2011, 03:06 PM   #15
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QuoteOriginally posted by axl Quote
If you are trying to avoid LBA don't post about it in here. Some very talented folks from here will maake you suffer from VERY severe case of LBA, and later CBA and later just I want it all BA...

Resistance is futile indeed!

Advice from me? Start saving, you'll need every penny!
Oh not trying to avoid it per se just wanted to make every penny count LOL

JJ
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