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Garrie
28th February 2008, 01:38 PM
Hi All,

Just a real quick question if you don't mind.

Whats the oly F value Equivalent of Canon 400D F22?

Cheers
G

j.baker
28th February 2008, 02:12 PM
I maybe wrong, but I though the F value was for the amount of light let though the lens, so shouldn't it be the same?

Garrie
28th February 2008, 02:17 PM
sorry I meant aperture F value

ianc
28th February 2008, 02:20 PM
The equivalent of f22 is f22. An f number is an f number no matter the system neg/sensor size or focal length. It is a ratio of the width of the aperture to the distance to the film/sensor plane.

Ian C.

andym
28th February 2008, 02:49 PM
Garrie

Are you asking about DOF???

Garrie
28th February 2008, 02:57 PM
Hi Andy,

Yeah I thats what I'm meaning, I'm rubbish at explaining stuff :(

Cheers

andym
28th February 2008, 03:05 PM
Try these from Andrzej Wrotniak brilliant site.I believe DOF is greater for 4/3 cameras due to the smaller sensor.


http://www.wrotniak.net/photo/tech/dof-43.html

http://www.wrotniak.net/photo/tech/dof.html

Garrie
28th February 2008, 03:11 PM
MINT - Cheers Andy

Ian
28th February 2008, 03:34 PM
Please remember that from F5.6 onwards your lens will deliver softer and softer images - f/22 is to be avoided if at all possible. f/5.6-f/6.3 is the sweet spot for Four Thirds cameras. The softness as the aperture gets smaller is due to the effects of diffraction along the edges of the aperture blades at very small physical aperture sizes.

Ian

E-P1 fan
28th February 2008, 04:16 PM
Please remember that from F5.6 onwards your lens will deliver softer and softer images - f/22 is to be avoided if at all possible. f/5.6-f/6.3 is the sweet spot for Four Thirds cameras. The softness as the aperture gets smaller is due to the effects of diffraction along the edges of the aperture blades at very small physical aperture sizes.

Ian

Thanks Ian - I didn't know that :o Maybe that's why I'm often disatisfied with the sharpness of my E-1?

Scapula Memory
28th February 2008, 04:22 PM
Please remember that from F5.6 onwards your lens will deliver softer and softer images - f/22 is to be avoided if at all possible. f/5.6-f/6.3 is the sweet spot for Four Thirds cameras. The softness as the aperture gets smaller is due to the effects of diffraction along the edges of the aperture blades at very small physical aperture sizes.

Ian

Thats interesting, I have been led to believe the sweet spot on the 14-54 was nearer F16 before diffraction set in? Any landscape togs here wish to comment? Also does this differ with different lenses. I have had what I consider poor results on anything landscape wise where DOF was needed.

Ian
28th February 2008, 04:38 PM
Thats interesting, I have been led to believe the sweet spot on the 14-54 was nearer F16 before diffraction set in? Any landscape togs here wish to comment? Also does this differ with different lenses. I have had what I consider poor results on anything landscape wise where DOF was needed.

Here is a plot of the sharpness of a 50mm f/2 Digital Zuiko through its aperture range. The smaller the (DxO Blur Experience Unit or BXU the less blurred (more sharp) the lens is) :

http://fourthirds-user.com/images/olydz50macrobxu.PNG

There probably isn't a lens much sharper than this in Four Thirds and the edge/edge sharpness is very uniform, even at full aperture.

You can see that sharpness peaks at f/2.8 here, but f/16 is quite a way down.

Ian

Ian
28th February 2008, 04:41 PM
Thanks Ian - I didn't know that :o Maybe that's why I'm often disatisfied with the sharpness of my E-1?

E-1s, by default, have minimal sharpening set, so you should have plenty of sharpening latitude in post processing.

Ian

E-P1 fan
28th February 2008, 04:47 PM
I hate using it though Ian - I know it's daft but still feels like cheating :)

I'd much rather get the basics right in camera if possible.

Do you have similar charts for the 35mm ZD and the 40 -150mm?

I'd love to know the optimum aperture for both of these too

Scapula Memory
28th February 2008, 04:48 PM
Excellent post Ian, thanks, that is very interesting to see. Quite a difference from F11 onwards. This explains a few things about some of my pictures from the Lakes last year.

Garrie
28th February 2008, 05:08 PM
Great posts Ian, thanks.

I'm gonna try these out tomorrow on my new lastest explore.

Cheers

Ian
28th February 2008, 05:17 PM
I hate using it though Ian - I know it's daft but still feels like cheating :)

I'd much rather get the basics right in camera if possible.

Do you have similar charts for the 35mm ZD and the 40 -150mm?

I'd love to know the optimum aperture for both of these too

Probably, but I'm rebuilding my desktop PC at the moment so it will have to be a few days...

Ian

Barr1e
28th February 2008, 06:21 PM
Ian -

Thanks - especially as I read somewhere recently to go up scale so as to speak. You have probably saved me a lot of frustration.


Regards. Barr1e

Xpres
28th February 2008, 06:51 PM
This is a very interesting thread indeed - I realised that diffraction was a problem at small apertures but had no idea it set in so soon.

Is this an issue with digital sensors in general is it it just the smaller ones?

There would seem to be implications for a lot of landscape work if the useable apertures are so limited.

There also seems to be some confusion over depth of field with a 4/3 sensor. Am I right in thinking a lenses dof is not going to change whatever the film/sensor size, it is only the apparent dof that seems to be different when you try and compare images with the same field of view made with different lens and sensor combinations?

Sorry about that - this was mentioned in another thread and I think needs clarifying. Does someone in 'the know' want to make it clear?

E-P1 fan
28th February 2008, 06:58 PM
Thanks Ian - when you can that would be great - or a link to see them online if easier

andym
28th February 2008, 07:45 PM
As I understand it the more pixels you have the sooner the diffraction limit sets in.
I seem to remember reading somewhere thet on the 5M pixel E1 it did not set in until about F14 but on a 10M pixel camera ie E410,510,3 it was about F11.
Unless I want to isolate an object I usually am between f6.3 to F8.
On the E1 I have used F16 not realy noticed much difference but you can see the problem at F22.
So far on the E3 Ive only gone down to about F11 and all looks OK.
See what happen if we get a nice bright summer though.

Sam M
29th February 2008, 01:38 AM
Very interesting and I'm quite shocked!

Is this the same with all lenses?

I always appreciated that smaller apertures were going to be less sharp but assumed that was why apertures were capped at f22 on most lenses. But that f8 and f16 were still going to be super sharp along with the added depth of field.

Sam

Ian
29th February 2008, 09:39 AM
The size of the sensor pits, which is partially determined by the sensor size and pixel count, is a factor yet. The difference between a 5MP E-1 and a 10MP E-series camera is roughly 1 stop in terms of the diffraction limit setting in, so around f/5.6 for a 10MP camera and f/8 for an E-1.

The diffraction limit is primarily determined by the aperture size in the lens and I don't think it varies greatly between different lenses of the same focal length.

Ian

dbutch
29th February 2008, 11:27 AM
Interesting that some manufacturers these days are having their base ISO at 200, with the diffraction issues I would of thought an option of lower ISO's would be prefered say 50 but could be lower!

Maybe I need to look out that menu cheat that lets you set it on the E-system cameras

I have noticed that my E-400 is softer at f11 than my E-1 with the same lens

Cheers

Dave

Ian
29th February 2008, 11:59 AM
Interesting that some manufacturers these days are having their base ISO at 200, with the diffraction issues I would of thought an option of lower ISO's would be prefered say 50 but could be lower!

Maybe I need to look out that menu cheat that lets you set it on the E-system cameras

I have noticed that my E-400 is softer at f11 than my E-1 with the same lens

Cheers

Dave

I suspect that CCDs from Sony that were limited to 200ISO rather than 100ISO were susceptible to over-saturation at 100, causing leakages between photosites.

Some of the Konical Minolta DSLRs with Sony sensors let you go to 100 ISO and I noticed noise performance was better at 200ISO.

Big pixels are not always a guarantee of low noise. The Contax N1 Digital, which was one of the first full frame DSLRs had humungous photosites, being just 6 megapixels. But that sensor was notoriously noisy.

Your experience comparing f/11 on your E-400 with f/11 on the E-1 is right in the mark.

Ian

HughofBardfield
29th February 2008, 12:13 PM
I was told f11 was the effective limit for macro, so that graph makes perfect sense. I hadn't realised it would start to set it quite as early as it does though. Quite an eye-opener.

I normally shoot around f5.6-8 as a hangover from my customary film settings, so at least I'm doing the right thing, even if it's by accident. Of course, sharpness isn't everything!