"What goes round, comes around" - it must be F8


PeterKR

Link Posted 11/04/2013 - 19:49
Strange how "What goes round comes around" is so true !

When I was a student 50 years ago, just starting 35mm photography with a Kodak Retinette with a 45mm fixed lens, using Govt surplus bulk FP3 that I loaded onto old cassettes in the University darkroom, I found that I shot most things at 1/125 at f/8 so used this as my ‘normal setting’. I did all my own developing and enlarging so played around with the image during developing - changing the print exposure time and rubbing the light spots to bring them up etc !

Now we are in the digital age with 'all singing and dancing' cameras that can do everything for us I've tended to get a bit 'lazy' leaving my K-r on 'P' most of the time ! I've also expected the lenses to perform well even 'wide open' - after all why buy a fast lens and stop it down ?

However, after getting some disappointing results from the 18-55 kit lens and reading the various postings on this Forum I now realise that MOST lenses need stopping down and, guess what, f/8 is a very good option and that seems to be the general concensus!

From now on I guess 'P' will be dropped in favour of 'Av' and I'll play with the ISO to get the shutter speed right ! At least the K-r does perform quite well at high ISO’s so this should compensate for the lower light input from smaller apertures ? What is more, we can play around even more with our digital images using numerous items of software.

As one respondent said on the thread I posted on the freebie e-books "you are always learning, and that's half the fun !"

How true ! And it’s also one reason I keep watching this Forum - there is always something to add to the ‘fun’ !

Peter

Mannesty

Link Posted 11/04/2013 - 20:27
You might find TAv exposure mode interesting on some of the other Pentax bodies, I think the K20D was the first to have it. As its name suggests, you set the aperture and shutter speed, leaving the camera to choose the ISO for correct exposure.

I use it quite a lot.
Peter E Smith

My flickr Photostream

Smeggypants

Link Posted 11/04/2013 - 20:32
PeterKR wrote:


However, after getting some disappointing results from the 18-55 kit lens and reading the various postings on this Forum I now realise that MOST lenses need stopping down and, guess what, f/8 is a very good option and that seems to be the general concensus!

I would disagree with this and also disagree that it's any kind of consensus.

The aperture you set on the lens is dependant on how you want to shoot something,as well considerations of getting enough light for a particular shutter speed. There's no setting that is "better"

I often like shooting with a narrow DOF and for that I will shoot with the lens wide open. Not just with my 50/1.2, 50/1.4 and sigma 30/1.4 ( all of which remain wide open 95% of the time, but I also shoot with my 50-135 at 2.8 very often.

Other times I want more DOF in the shot and will stop down accordingly.

No lens needs stopping down. If there is any general consensus I think it would be "You stop down ( or not ) according to your own shooting wishes for each particular shot"


[i]Bodies: 1x K-5IIs, 2x K-5, Sony TX-5, Nokia 808
Lenses: Pentax DA 10-17mm ED(IF) Fish Eye, Pentax DA 14mm f/2.8, Sigma 17-70mm f/2.8, Pentax-A 28mm f/2.8, Sigma 30mm F1.4 EX DC, Pentax-A 50mm f/1.2, Pentax-A 50mm f/1.4, Pentax-FA 50mm f/1.4, Pentax-A 50mm f/1.7, Pentax DA* 50-135mm f/2.8, Sigma 135-400mm APO DG, and more ..
Flash: AF-540FGZ, Vivitar 283

Smeggypants

Link Posted 11/04/2013 - 20:36
Mannesty wrote:
You might find TAv exposure mode interesting on some of the other Pentax bodies, I think the K20D was the first to have it. As its name suggests, you set the aperture and shutter speed, leaving the camera to choose the ISO for correct exposure.

I use it quite a lot.

Me too. I'm using TAv mode more and mroe these days. Aperture on front wheel, speed on rear wheel
[i]Bodies: 1x K-5IIs, 2x K-5, Sony TX-5, Nokia 808
Lenses: Pentax DA 10-17mm ED(IF) Fish Eye, Pentax DA 14mm f/2.8, Sigma 17-70mm f/2.8, Pentax-A 28mm f/2.8, Sigma 30mm F1.4 EX DC, Pentax-A 50mm f/1.2, Pentax-A 50mm f/1.4, Pentax-FA 50mm f/1.4, Pentax-A 50mm f/1.7, Pentax DA* 50-135mm f/2.8, Sigma 135-400mm APO DG, and more ..
Flash: AF-540FGZ, Vivitar 283

McGregNi

Link Posted 11/04/2013 - 22:35
If we're talking about image quality, and I'm guessing that's what Peter was referring to (ie lens performance) then I do think it is fair to say that 'the consensus' is that there a 'sweet spot' for lenses generally, at least for anything below professional-grade primes, certainly for zooms, and this is very often placed at f8.0.

Certainly from most photography books or mag articles I've seen over the years this does seem to be a reasonably consistent idea. Put it this way, if your main consideration is extraxcting the highest 'quality' (in scientifically measurable aspects) then f8.0 for most lenses would be a good starting point - is that not fair to say?

Of course if DOF is the main reason you are choosing a particular aperture, then you are stuck, either with a compromise (on a lower quality lens) or possibly less compomise ,if you're lucky, on the highest quality lenses. But DOF is not the only consideration in choosing aperture. Finding that 'sweet spot' may well be desirable as well.

Our Cameras have the MTF program line function (when shooting in P), to
automatically aim for the optimal aperture (on DA lenses ony) - I'd hazard a guess that f.8 might feature in this mode fairly often - maybe you could test this Peter?
My Guides to the Pentax Digital Camera Flash Lighting System : Download here from the PentaxForums Homepage Article .... link
Pentax K7 with BG-4 Grip / Samyang 14mm f2.8 ED AS IF UMC / DA18-55mm f3.5-5.6 AL WR / SMC A28mm f2.8 / D FA 28-105mm / SMC F35-70 f3.5-4.5 / SMC A50mm f1.7 / Tamron AF70-300mm f4-5.6 Di LD macro / SMC M75-150mm f4.0 / Tamron Adaptall (CT-135) 135mm f2.8 / Asahi Takumar-A 2X tele-converter / Pentax AF-540FGZ (I & II) Flashes / Cactus RF60/X Flashes & V6/V6II Transceiver

McGregNi

Link Posted 11/04/2013 - 22:42
Reagarding Tav mode (where the camera sets ISO following user set Av & Tv), this is obviously useful when a particular aperture (say for quality purposes) and shutter speed (say for movement depiction) are needed - this would be a rare occaision I hazard to suggest

But surely we should be cautious in this mode, as even with our modern K5s the variation in quality as the ISO shoots up is surely greater than would be seen if the aperture were to open up instead ?? (Smeggy, this is a hint for you to post the 'Rasta Alien' image again)

At least the lesser experienced of us should be wary of introducing noise into our shots that may be missed on the LCD, but be disappointing when printed out. Is it not good advice to suggest that we should aim to keep ISO's as low as practical in the available light, in the interests of the best quality?
My Guides to the Pentax Digital Camera Flash Lighting System : Download here from the PentaxForums Homepage Article .... link
Pentax K7 with BG-4 Grip / Samyang 14mm f2.8 ED AS IF UMC / DA18-55mm f3.5-5.6 AL WR / SMC A28mm f2.8 / D FA 28-105mm / SMC F35-70 f3.5-4.5 / SMC A50mm f1.7 / Tamron AF70-300mm f4-5.6 Di LD macro / SMC M75-150mm f4.0 / Tamron Adaptall (CT-135) 135mm f2.8 / Asahi Takumar-A 2X tele-converter / Pentax AF-540FGZ (I & II) Flashes / Cactus RF60/X Flashes & V6/V6II Transceiver

PeterKR

Link Posted 11/04/2013 - 22:52
Smeggypants wrote:
[quote:3496ace15f="PeterKR"]

I often like shooting with a narrow DOF and for that I will shoot with the lens wide open. Not just with my 50/1.2, 50/1.4 and sigma 30/1.4 ( all of which remain wide open 95% of the time, but I also shoot with my 50-135 at 2.8 very often.

Other times I want more DOF in the shot and will stop down accordingly.

No lens needs stopping down. If there is any general consensus I think it would be "You stop down ( or not ) according to your own shooting wishes for each particular shot"


Yes, I agree that if you want a narrow DOF then you need to open up as wide as possible.
However, with most lenses within economic reach of the average amateur photographer that means a compromise in image quality.

Likewise, if you want the best IQ then I would suggest that all moderately priced lenses DO need stopping down.

Before posting this thread I looked at lots of lens reviews, including those of several costing £500 or more and the reviewers generally found that IQ DID improve at around f/8 - that's one of the reasons I called it a 'concensus'.

However, I'm glad this has prompted some debate - that's what I was hoping for !

Peter

Smeggypants

Link Posted 11/04/2013 - 23:35
I guess it depends upon what you define as Image Quality.

For example, personally I don't place lens sharpness very high up on my priorities for what defines a quality image. I know some people can be obsessed by it, but each to their own.


So if you're defining IQ as MTF ( resolution ) then ...


Quote:
Yes, I agree that if you want a narrow DOF then you need to open up as wide as possible.
However, with most lenses within economic reach of the average amateur photographer that means a compromise in image quality.

Well yes of course it does, but you can't get that narrow 1.2/1.4 DOF at F8 so it's irrelevant

Quote:

Likewise, if you want the best IQ then I would suggest that all moderately priced lenses DO need stopping down.

I think ALL Lenses regardless of price will have a higher resolution stopped down a bit.

I just checked the MTF graphs for my lenses at Ephotozone

http://www.photozone.de/Reviews/overview#pentax

And the MTF peak was an even spread of F4, F5.6 and F8.0. The wider prime lenses had their peak at F/4.0. So there's no consensus F8 is a resolution sweet spot amongst my lens collection

Don't get me wrong, I do like sharp noise free images, but for me they are a bonus.

I think my photography would greatly suffer if I started choosing settings based upon sweet spot MTF figures or lowest noise, rather than choosing settings based upon what I think is artistically good for the scene I'm trying to capture.
[i]Bodies: 1x K-5IIs, 2x K-5, Sony TX-5, Nokia 808
Lenses: Pentax DA 10-17mm ED(IF) Fish Eye, Pentax DA 14mm f/2.8, Sigma 17-70mm f/2.8, Pentax-A 28mm f/2.8, Sigma 30mm F1.4 EX DC, Pentax-A 50mm f/1.2, Pentax-A 50mm f/1.4, Pentax-FA 50mm f/1.4, Pentax-A 50mm f/1.7, Pentax DA* 50-135mm f/2.8, Sigma 135-400mm APO DG, and more ..
Flash: AF-540FGZ, Vivitar 283
Last Edited by Smeggypants on 11/04/2013 - 23:35

johnriley

Link Posted 11/04/2013 - 23:50
It's an area where theory and reality diverge, basically because there is no such thing as a "perfect" lens.

In theory, a 50mm f/1.2 lens will perform best at f/1.2 and diffraction will take the edge off that progressively as we stop down.

In practice, the "rule of thumb" is that performance peaks at two stops down. For an f/2 lens this would be f/4, but this may or may not be true. Generally, expensive lenses are better built and peak closer to the theory. Cheaper lenses may not reach peak performance till f/11. Really poor lenses will just keep getting better as you stop down.

As I have a collection of good Pentax lenses, I worry more about the effects of depth of field than resolution when I'm selecting which aperture to use.
Best regards, John

McGregNi

Link Posted 12/04/2013 - 00:21
We all come at this from our own perspectives I can see! In my case, I am getting my best shots printed at 100 x 70 cm for wall display. I simply must maximise whatever 'qualities' I can muster from my camera and lens.

I say 'qualities', because its not just about 'sharpness' (which I personally feel could be achieved in a variety of ways for any given output size - you can make pictures 'sharp' with many different editing techniques) - but things like vignetting, distortions and abberations are affected by F-stop settings surely?

In my case (yes, I only have a K7), for the printed sizes I mentioned, I don't want to capture any noise if poss, and I certainly don't want to introduce any signs of noise reduction processes going on also. So I need the lowest ISO I can shoot steadily at.

Apart from my Samyang 14mm (the only lens I possess that might approach the 'pro prime' designation) my lenses are more standard, and at my output sizes I'll be seeing a falloff in IQ particularly at the edges if I started shooting wider than f 8.0.
My Guides to the Pentax Digital Camera Flash Lighting System : Download here from the PentaxForums Homepage Article .... link
Pentax K7 with BG-4 Grip / Samyang 14mm f2.8 ED AS IF UMC / DA18-55mm f3.5-5.6 AL WR / SMC A28mm f2.8 / D FA 28-105mm / SMC F35-70 f3.5-4.5 / SMC A50mm f1.7 / Tamron AF70-300mm f4-5.6 Di LD macro / SMC M75-150mm f4.0 / Tamron Adaptall (CT-135) 135mm f2.8 / Asahi Takumar-A 2X tele-converter / Pentax AF-540FGZ (I & II) Flashes / Cactus RF60/X Flashes & V6/V6II Transceiver
Last Edited by McGregNi on 12/04/2013 - 00:22

Smeggypants

Link Posted 12/04/2013 - 01:56
McGregNi wrote:
We all come at this from our own perspectives I can see! In my case, I am getting my best shots printed at 100 x 70 cm for wall display. I simply must maximise whatever 'qualities' I can muster from my camera and lens.

I say 'qualities', because its not just about 'sharpness' (which I personally feel could be achieved in a variety of ways for any given output size - you can make pictures 'sharp' with many different editing techniques) - but things like vignetting, distortions and abberations are affected by F-stop settings surely?

... can be removed in editing, just like images can be sharpened.

btw - I add a smidgeon of vignetting to a fair portion of my pics in lightroom.



Quote:

In my case (yes, I only have a K7), for the printed sizes I mentioned, I don't want to capture any noise if poss, and I certainly don't want to introduce any signs of noise reduction processes going on also. So I need the lowest ISO I can shoot steadily at.

Apart from my Samyang 14mm (the only lens I possess that might approach the 'pro prime' designation) my lenses are more standard, and at my output sizes I'll be seeing a falloff in IQ particularly at the edges if I started shooting wider than f 8.0.

but in some cases it doesn't matter. No need for super resolution for bokeh...

f/1.2


[/quote]
[i]Bodies: 1x K-5IIs, 2x K-5, Sony TX-5, Nokia 808
Lenses: Pentax DA 10-17mm ED(IF) Fish Eye, Pentax DA 14mm f/2.8, Sigma 17-70mm f/2.8, Pentax-A 28mm f/2.8, Sigma 30mm F1.4 EX DC, Pentax-A 50mm f/1.2, Pentax-A 50mm f/1.4, Pentax-FA 50mm f/1.4, Pentax-A 50mm f/1.7, Pentax DA* 50-135mm f/2.8, Sigma 135-400mm APO DG, and more ..
Flash: AF-540FGZ, Vivitar 283

johnwhit

Link Posted 12/04/2013 - 07:25
McGregNi wrote:

Our Cameras have the MTF program line function (when shooting in P), to
automatically aim for the optimal aperture (on DA lenses only)

IIRC FA lenses do as well.

John
PPG link

In LBA hiatus.

gartmore

Link Posted 12/04/2013 - 07:50
And you will find that they only stop down by one stop or so, F8 is never used. I should say that P-MTF is my default mode
Ken
“We must avoid however, snapping away, shooting quickly and without thought, overloading ourselves with unnecessary images that clutter our memory and diminish the clarity of the whole.” - Henri Cartier-Bresson -

wvbarnes

Link Posted 12/04/2013 - 09:59
Hi all,

I'm increasingly a fan of the TAV mode on my K5 as I can see where I start from much as in film days.

We were taught to set our manual film cameras to F8 at 1/125th set at about 20 feet for a 100 ISO film as this meant if you used the camera in a hurry out of the 'ever ready' case you would likely get a reasonable shot.

Nowadays in TAV it depends on what you are up to. For example if the telephoto is on I have it ready at 1/500th and F8 allowing the ISO to float BUT as others have inferred its only a starting point out of the bag if an intertesting bird is spotted for example.

If out taking landscapes it's a more relaxed affair and I'd be looking for low ISO under my control to keep as much dynamic range as possible. The aperture then might well be about depth of field considerations if there are foreground objects although with the 15mm on thi is not a big issue..

So F8 has is place but that's all.
Last Edited by wvbarnes on 12/04/2013 - 09:59

DaveHolmes

Link Posted 12/04/2013 - 10:57
I use Tav mode a lot too... Very good in low light with the FA35... I just whack it on f3.2 at 1/80 and its bang on for handheld lowlight snapshots...
........................................................................
Digital:
Pentax K5- Vivitar 19mm 3.8; FA35mm f2; D-Xenon 100mm macro f2.8; DA50-200mm WR...
Flash:
Yongnuo YN-560; Vivitar 285HV; Cactus V4 triggers...
Film:
Pentax-MX & M50mm f1.4; Spottie & 55mm f1.8; MG & M40mm 2.8...

http://www.flickr.com/photos/daveholmesphotos/
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