# Sharpest f stop?



## six-five-two (Sep 25, 2007)

problem solved: f/22


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## usayit (Sep 25, 2007)

It depends on the lens.. but for the typical lens, increased sharpness usually starts 1-2 stops in from the max aperture.  Some lenses are sharp even wide open.

For landscapes with max depth of field, I'll shoot usually at f/11 or f/16.


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## jstuedle (Sep 25, 2007)

The term "F8 and be there" was coined for a reason. Most glass has a "Sweet Zone" around f/8-11. But as mentioned above, some are designed to be sharpest wide open. The old MF Nikkor 400 f/3.5 comes to mind. Every lens is differant, ever the same model lens from the same production run will have piece to piece variations. Use it, test it, and decide what works best for you and your style and equipment.


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## skieur (Sep 25, 2007)

If you read the lab reports on particular lenses as I do, then you realize that it is often f2.8 or f4.

skieur


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## Garbz (Sep 25, 2007)

Skieur what kind of lenses are you using that are sharpest at f/2.8???? Mostly the sharpness curves follow the standard bell curve for a reason.

Normally they are sharpest 2-3 stops from wide open. On an f/1.8 lens it may be f/4-5.6 is sharpest. On my 18-70 it's around f/8. One thing important to note is that at f/11 diffraction on a digital camera causes a loss of sharpness. On a film camera or a full frame sensor camera like the Canon 5D this is around f/16.


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## skieur (Sep 25, 2007)

Garbz said:


> Skieur what kind of lenses are you using that are sharpest at f/2.8???? Mostly the sharpness curves follow the standard bell curve for a reason.
> 
> Normally they are sharpest 2-3 stops from wide open. On an f/1.8 lens it may be f/4-5.6 is sharpest. On my 18-70 it's around f/8. One thing important to note is that at f/11 diffraction on a digital camera causes a loss of sharpness. On a film camera or a full frame sensor camera like the Canon 5D this is around f/16.


 
Minolta and Tokina.

skieur


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## Iron Flatline (Sep 25, 2007)

Many Leica lenses are sharpest at maximum aperture. 

"F8 and be there" means you can turn your camera into a nice Point-and-Shoot whereby your DOF makes almost everything more than five-to-six feet away in focus.


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## usayit (Sep 25, 2007)

skieur said:


> Minolta and Tokina.
> 
> skieur



Specifics.?  I'm curious too....  not too many lenses that have their sharpest aperture at max aperture.

Leica have some sharp lenses at max but even those show improvement as you stop down.  35mm f/1.4 Summilux asph for example.. >>read<< expensive.


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## six-five-two (Sep 26, 2007)

The two lenses I have is the Pentax 75-300mm f/4.5 f/5.8 (my zoom lens) and my primary lens: Pentax 18-55mm K100D Kit Lens.


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## jon_k (Sep 26, 2007)

skieur said:


> If you read the lab reports on particular lenses as I do, then you realize that it is often f2.8 or f4.
> 
> skieur



Where can you get the reports / data / graphs and how do you interpret the data? Can you share more information.

Everyone says each model lens has a different sweet spot. Where's the site that reports lenses and their sharpest apertures.


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## abraxas (Sep 26, 2007)

f22-f32 for my stuff.


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## Case (Sep 26, 2007)

Noob post engage..

So basically Fstop is Aperture? And Aperture is the amount of light let into a lens when taking a picture?

So basically higher Aperture settings make for a sharper, more clear image? 

When a lens says f/4-5.6 does that mean the HIGHEST Aperture setting that lens can be set to is 5.6?

Sorry for the noobish questions, we all have to start somewhere.


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## Patrolman Pat (Sep 26, 2007)

Case said:


> Noob post engage..
> 
> So basically Fstop is Aperture? And Aperture is the amount of light let into a lens when taking a picture?
> 
> ...


 
f/4-5.6 would be found on a zoom lens. f4 would be at the shortest focal length of that lens, f5.6 at the longest focal length.

Prime lenses would be quoted with one f number.


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## ann (Sep 26, 2007)

the higher the fstop number the greater the depth of field.

the fstop numbers on the lens are the widest fstop available at the shortest and longest focal lengths. Lower number fstops = less DOF


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## abraxas (Sep 26, 2007)

I try not to concern myself with the technicals, but before the wizards wake up and explain it correctly, the following works for me;

f/stop is aperature.  The larger the number, the smaller the little hole, the less light let in.  This and using a slow(?) iso like 100 results in longer shutter speeds.  I like the thorough depth of field I get. Tripod and remote cable are necessary.  

I learned this twice- once in high school many years ago and again about 10 years ago when I first read about the f/64 club.

I'm waiting, and this could be forever, for a camera, hopefully Nikon that has ISO of 50 or even 25. This would be cool to me.  Looks like it's going the other way though.


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## Big Mike (Sep 26, 2007)

> So basically Fstop is Aperture? And Aperture is the amount of light let into a lens when taking a picture?


The F-stop or F number is a ratio between the focal length and the diameter of the aperture opening.  F4 is actually 1/4 which means that the aperture's diameter is one quarter of the focal length.

'Aperture' is not the amount of light coming into the lens...but a larger aperture lets is more light.  Smaller F numbers represent larger apertures.



> So basically higher Aperture settings make for a sharper, more clear image?


That might be a simplistic way of looking at it...but for the most part, yes.  The higher (smaller) the aperture...the more DOF you have, so more things may be in focus.  However, as people are pointing out...each lens seems to have a 'sweet spot' which is sharpest.  I have always heard and found that most lenses are best from...one or two stops from wide open...to F8 or F11.


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## Garbz (Sep 26, 2007)

abraxas that's not going to happen. If anything the ISO will keep going up as it becomes harder to make sensors with high ISO and low noise insensitive to light. Look at the D200 (ISO100) D300 and D3 (ISO200). To go slow you'll have to get ND filters. They may even come standard in the lens of the future 

six-five-two: http://www.photozone.de/8Reviews/lenses/pentax_1855_3556/index.htm that's your 18-55. Actually not all that sharp anywhere really but the lens is very consistent. Slight but probably not notable edge at f8.

skieur: Out of all the f/2.8 from minolta and tokina lenses none of them are perfectly diffraction limited (i.e. sharpest at f/2.8). They all follow the pretty normal bell curve and are sharpest at around f/5.6 (mostly 2 stops from open):
http://www.photozone.de/8Reviews/lenses/tokina_1650_28_nikon/index.htm
http://www.photozone.de/8Reviews/lenses/tokina_50135_28_nikon/index.htm
http://www.photozone.de/8Reviews/lenses/tokina_100_28/index.htm
http://www.photozone.de/8Reviews/lenses/minolta_50_17/index.htm
http://www.photozone.de/8Reviews/lenses/minolta_85_14/index.htm


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## kundalini (Sep 26, 2007)

Nice link Garbz.  Cheers.


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## The_Traveler (Sep 26, 2007)

Can anyone point me to a tutorial on reading/understanding these kinds of sharpness charts?


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## Helen B (Sep 26, 2007)

You could start at Norman  Koren's site (look for the 'Understanding MTF' page, among others) and the affiliated site dedicated to Imatest, his software that is used for the Photozone tests. I have a little experience with Imatest, so might be able to answer some questions.

One thing to remember is that these results are for the plane of perfect focus. They do not represent the sharpness of objects that are in perfect focus away from the film plane - ie they do not tell you how sharp the image of something will be when it is not in perfect focus. In most photographs of three-dimensional items very few parts will be in perfect focus. 

Best,
Helen


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## xfloggingkylex (Sep 26, 2007)

Great link Garbz.  I had no idea that diffraction can start as early as f/8.  Here I had been thinking my 50 1.4 was sharpest at f/8 but in reality thats where diffraction starts, and 5.6 is the sweet spot.


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## The_Traveler (Sep 26, 2007)

Helen B said:


> You could start at Norman  Koren's site (look for the 'Understanding MTF' page, among others) and the affiliated site dedicated to Imatest, his software that is used for the Photozone tests. I have a little experience with Imatest, so might be able to answer some questions.
> 
> Best,
> Helen



Thank you for excellent refs.
I looked at your "snaps' and especially liked  http://www.usefilm.com/image/1178410.html


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## abraxas (Sep 26, 2007)

Garbz said:


> abraxas that's not going to happen. If anything the _ISO will keep going up as it becomes harder to make sensors with high ISO and low noise insensitive to light_. Look at the D200 (ISO100) D300 and D3 (ISO200). To go slow you'll have to get ND filters. They may even come standard in the lens of the future ...



I sort of thought so...  As long as I don't have to change too much- Or learn stuff.  Maybe just keep it simple, things I can ask instead of lookup. 

The future sounds complex.


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## six-five-two (Sep 26, 2007)

Garbz, is there any other 18-55mm Pentax lenses that will fit on my K100D that is sharpest then the kit lens? Because I think there is only one type of 18-55 made by Pentax for the K100D mount thingy...


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## six-five-two (Sep 26, 2007)

I also did a small experiment, went to some website with pictures taken by the Pentax K100D. Wrote down 33 aperture settings then averaged it.. the average is 8. So apertures 8-11 should be good.


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## xfloggingkylex (Sep 27, 2007)

six-five-two said:


> Garbz, is there any other 18-55mm Pentax lenses that will fit on my K100D that is sharpest then the kit lens? Because I think there is only one type of 18-55 made by Pentax for the K100D mount thingy...


 
check out third party lenses such as sigma.  They have some excellent 18-50 2.8 lenses, and IM sure they will have something around the kit level.


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## six-five-two (Sep 27, 2007)

Well I found a Pentax 18-50mm lens. I saw pictures and they were fantastic... then I looked at the price and my jaw dropped... $900 for that lens. Damn!

Searched for some Sigma lenses. The cheapest one was $180 and was worse quality then my kit lens. I guess good lenses are about $600-900... you get what you pay for. Thanks for all your help though.


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## xfloggingkylex (Sep 27, 2007)

sigmas 18-50 2.8 is like 400.


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## Iron Flatline (Sep 28, 2007)

abraxas said:


> I'm waiting, and this could be forever, for a camera, hopefully Nikon that has ISO of 50 or even 25. This would be cool to me.  Looks like it's going the other way though.


The Canon 5D (and probably several other high-end Canon cameras) have ISO 50.


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## jstuedle (Sep 28, 2007)

abraxas said:


> I learned this twice- once in high school many years ago and again about 10 years ago when I first read about the f/64 club.
> 
> I'm waiting, and this could be forever, for a camera, hopefully Nikon that has ISO of 50 or even 25. This would be cool to me.  Looks like it's going the other way though.



As sensors get more advanced, their native ISO, the minimum ISO to fully saturate the individual pixel without amplification, will only go up. Early sensors needed more light to expose the chip. As we get sensors with lower noise levels, the higher the minimum ISO will be. This is a very good thing. We are seeing image quality going up while minimum ISO is going up as well. I do long for good glass with smaller minimum apertures. I would love to see all prime lenses to have at least a min. aperture of f/32 or f/45. And it would not bother me to see my macro lenses have a min. aperture of f/64. Just another thing on my wish list.


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## Garbz (Sep 29, 2007)

six-five-two: 
Sorry I don't know enough about Pentax lenses to recommend one. One thing you probably shouldn't do is get too caught up on the numbers. Yes sharper is better, and so is low vignetting and low CA. But ultimately the softness of the image will not be apparent until you start using your sensor to its fullest. A 10x8 print will look tac sharp with even a crap kit lens. It's when you zoom in 100% on the monitor, or start printing A3+ sizes that you need to worry about sharpness of lenses.

xfloggingkylex:
Diffraction is like a noise floor that gets worse as the aperture closes. It exists in every f-stop. Diffraction sets in at apertures where the sharpness peaks. So if the lens is sharpest at f/8 then at f/11 diffraction is starting to cause the problems. If it's sharpest at f/5.6 then at f/8 it's an issue. This is usually how it goes, but I am sure an optics expert can give a counter opinion. Also mounting one of the lenses on a full frame camera is likely to give you different resolution figures because the diffraction element changes based on sensor size.


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## Helen B (Sep 29, 2007)

There is a brief discussion about diffraction in this recent thread.

Best,
Helen


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## Antithesis (Sep 30, 2007)

I've read and been told that one stop from wide open is going to be your sharpest. I also have heard from people that f8 is going to be sharpest, but the one stop from wide open I learned in school so I'll stick with that.


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