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05-03-2010, 10:22 PM   #1
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F1.4 and F1.7..

do you really use these F stop? i have read lot of review and a lot of them say that its soft at F1.4 and F1.7 so why buy a lens with F1.4 if its not that usable?


Last edited by poogeek; 05-03-2010 at 10:27 PM.
05-03-2010, 10:38 PM   #2
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Usually a lens is sharpest a couple stops down from wide open, so the larger the maximum aperture is a better starting point.

The depth of field is very thin wide open, especially close up, so it takes some skillful focusing.
05-04-2010, 12:47 AM   #3
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I guess some people like the way the f1.4 renders, wide open or stopped down.

I chose the f1.7 obviously because it is sharp wide open (not sure if you're aware of that, and that it is sharper than the f1.4 when both are at f1.7)
05-04-2010, 01:06 AM   #4
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I use f1.7 alot. In the situation where it is the question of light, the picture will be sharper than with slower shutter speed or ISO1600 for example. So it's the best option. Unless the AF fails completely in a zzzzt-zzzzt manner.

At reasonable distances, the dof actually isn't that shallow. Even if you get per pixel sharpness in a very thin range, you still get acceptable definition around it.

In situations where there is enough light, i can usually get better results and have similar bokeh with f2..f2.5.

I've also had M50/1.4. I must admit that 1.4 was sort of an extreme. You could shoot very low light but not only the DOF was ridiculously thin, but the bokeh "progresses" much faster. Going too close to subject would result in "dot sharpness" - e.g. nose or eye is sharp and everything next to it is blurry and isolated. Going further away - risk missing the focus.

Attached a tomato shot: K200D, ISO320, 1/2000, SMC Pentax-F 50mm f/1.7 @ f/1.7.
Levels applied (it was underexposed), included closer crop and 100% crop.
I think it has plenty of sharpness in the detail i was after. And the other parts show just enough for the image to be reasonable. The hardest part was nailing focus. It would often lock on front face or branches behind, that is instantly visible at f/1.7.

Attached Images
View Picture EXIF
PENTAX K200D  Photo 

Last edited by ytterbium; 05-04-2010 at 01:16 AM.
05-04-2010, 01:29 AM   #5
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QuoteOriginally posted by poogeek Quote
do you really use these F stop? i have read lot of review and a lot of them say that its soft at F1.4 and F1.7 so why buy a lens with F1.4 if its not that usable?
You are assuming that sharpness is the only thing that matters !

Not so.
05-04-2010, 01:59 AM   #6
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QuoteOriginally posted by pschlute Quote
You are assuming that sharpness is the only thing that matters !

Not so.
no im just asking. im just a beginner thats why i want to know why and when to use them.
05-04-2010, 02:04 AM   #7
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I use all my fast lenses fully open, including the 50/1.4 or 1.2. There is a sligzht softness - so what? With a smaller aperture I would not be able to take the image I want to, may it be in very low light or because I want the extremely shallow depth of field.

Yes, there have been complaints about that said softness. But at least a large part of these complaints come from people who never used an 50/1.4, but are looking for a reason to justify why they choose a 50/1.7 over the 1.4. You will find similar complaints about almost any lens somewhere.

Also, with fast lenses, people often mistake the shallow depth of field which is followed immediately (almost abruptely) by unsharpness as a lack of contrast.

I personally find fast lenses indispensible and in many situations a slight contrast loss is very acceptable or even suitable for the subject (say with a 85/1.4 doinf a portrait).

Ben
05-04-2010, 04:31 AM   #8
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It might be the difference between a succesful photo and no photo (because it's too dark).

05-04-2010, 05:09 AM   #9
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QuoteOriginally posted by Eruditass Quote
I chose the f1.7 obviously because it is sharp wide open (not sure if you're aware of that, and that it is sharper than the f1.4 when both are at f1.7)
Can you point to any evidence of that? From things I've read it seems to be more of an opinion than a fact.
05-04-2010, 05:24 AM   #10
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you can always stop down f 1.4 to 1.7

i choose f1.7 because it is cheaper and im on a budget hehe
05-04-2010, 05:27 AM   #11
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You can't underestimate what a joy it is to look through a lens at F/1.4, not that 1.7 or 1.2 are that much different.

Over the course of the 35+ years I have been taking photos with an SLR, I have taken more photos with the 50mm/1.4 than any other lens. It is the sharpest lens in practice of any I have ever owned. The reason I say "in practice" is that focus at F/1.4 is so easy and accurate. Focus and hand shake are the biggest killers of resolution, if sharpness is important. The 50/1.4, often shot at F/4-5.6, 1/250 produced results on scenic shots that always did Kodachrome 25 proud.
05-04-2010, 05:42 AM   #12
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I've heard that some of F1.4 un-sharpness and F1.7 sharpness talk comes from the fact that the big piece of F1.4 glass sits right in front of the lens body.
In contrast F1.7 has a smaller element, deeper in lens having a "natural hood". This can reduce chromatic aberrations, lower contrast, haze and similar effects.

But this is true only for F/FA (or my smc tak 55/1.8), since M has same placement:




Still, i think most of the fast primes have degraded performance wide open. But this degradation is often negliable compated to what results the lens can deliver compared to slow zoom.

Last edited by ytterbium; 05-04-2010 at 05:47 AM.
05-04-2010, 06:11 AM   #13
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QuoteOriginally posted by ytterbium Quote
I've heard that some of F1.4 un-sharpness and F1.7 sharpness talk comes from the fact that the big piece of F1.4 glass sits right in front of the lens body.
In contrast F1.7 has a smaller element, deeper in lens having a "natural hood". This can reduce chromatic aberrations, lower contrast, haze and similar effects.
Interesting theory. As you say, the front element on the 1.4 is well out front. The FA 50 is sold without a lens hood, and it seems some people don't bother to use one. There were some photos posted a while ago of the FA 50 1.4 with/without a hood that made a very convincing case for using one. There's no excuse for not using a hood when the rubber ones sell for under $8.00.

The Photozone tests of the FA 50 1.4 and DA*55 showed the importance of contrast. Before PZ tested the DA*55, it was universally understood that the newer lens was sharper. It turns out the difference was in contrast, not resolution, giving the appearance of greater sharpness. The difference in contrast in this case was due to coatings, but certainly flare from a protuding front element and no hood wouold have a similar effect, a bleached looking image.

QuoteOriginally posted by ytterbium Quote
Still, i think most of the fast primes have degraded performance wide open. But this degradation is often negliable compated to what results the lens can deliver compared to slow zoom.
I wouldn't have any problem saying all lenses have degraded performance wide open, though some are more degraded than others. A lot of these softness complaints are exaggerated due to the effects of shallow dof and misfocus at large apertures, especially in tungsten light where the colour of the light fools the AF system (all Pentax cameras except K-7). I use f/2.0 most of the time in low light with the FA 50 because it's easier to handle and usually gives me enough light. I use 1.4 for bokeh effects or in very dim light.
05-04-2010, 06:50 AM   #14
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FA50/1.4 and FA50/1.7 comparison shots

QuoteOriginally posted by audiobomber Quote
Can you point to any evidence of that? From things I've read it seems to be more of an opinion than a fact.
I posted some comparison pictures about six months ago in this thread.

Below are the same pictures comparing the FA50/1.4 and FA50/1.7, both with and without a hood.

f=1.7

-------------
f=2.0

<br><br>
-------------
f=2.4

-------------
f=2.8

-------------
100% crops are here:
fa50_test Photo Gallery by dgaies at pbase.com
05-04-2010, 06:57 AM   #15
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QuoteOriginally posted by dgaies Quote
I posted some comparison pictures about six months ago in this thread.

Below are the same pictures comparing the FA50/1.4 and FA50/1.7, both with and without a hood.

Very good examples, which illustrate the advantages of using a lens hood very nicely. They also show a contrast advantage of th 1.7 lens at all the aperture settings, I must confess. But there are several factors (subject-to-lens distance being one of those factors, often forgotten, when looking at lens tests) , which may be responsible for the difference in contrast, not only lens quality.

Ben
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