Aperture F readings and Extenders EC14 & EC20

[birdboy]

I have read many threads on the use of teleconverter EC14 & EC20.

Please excuse me if this seems basic or wrong I want to share my experience of trying to use teleconverter.

Iam a novice trying to get the very best out of my E3 and telephoto combo. I dont like tweeking with software(yet) and only do the basics in Olympus Master 2.

I like many fellow olypians have struggled getting what I/we feel are good pictures from the teleconverter combination.

I have tried using this with a 50-200mm 2.8/3.5 SWD lens.

What is clear is that at small apeartures diffusion sets in and Ian's excellant article on this spells out the problem. Whats does not seem to be so well understood is aberation at full/near fully open apertures.

My first error was believing that large aperatures = sharper pictures.

Now using my 50-200mmswd lens the best aperture seems to be f8. It gives sharpness but limited depth of field but for birds that's fine for me.

What I was told was that the use of the EC20 teleconverter loses 2 stops. Now I took that to mean f2.8 + 2EV = f5.6 and f8 + 2EV = f16.

My next mistake was that I considered that according to the rules of diffraction when shooting at F16 you should see softer images, so avoid using this setting or anything above f11.

So I did some tests my 50-200mm lens on its own @ 200mm can be set be set between f3.5 and f22.

With the EC14 @200mm it becomes f4.9 to f32.

With the EC20 @200mm it becomes f7.0 to f45

It then struck me that the aperture belongs to the lens and there needs to be a mind set change regarding displayed aperture settings when using teleconverter.

It also struck me that the the displayed aperture valus are either 1.4 x using the EC14 and 2 x times using the EC20.

I have now started to use the 50-200 swd +EC 14 at a displayed F value of f11 and with the EC20 at a displayed value of f16.

The results I am getting are much better albiet I am having to use higher ISOs.

So my question to all those not getting the images you want with the EC20 is have you tried shooting at f16?

[benvendetta]

Re: Aperture F readings and Extenders EC14 & EC20

f16 is mighty high and would require ISOs that are at least 800 I guess. If you get along with the combo at f16 then fine but irrespective of the ISO I have found that the best aperture for the 50-200 (old version) plus the Ec20 is f9 and that requires good light at ISO 100. Depends what you are shooting I suppose but I use this combo for wildlife and birds mainly and I would rather keep in the 100 to 400 range if possible. However, I have never been really happy with it in combination with my E-3 and have wondered about getting the EC14 to improve IQ but at the expense of a loss of reach.

[birdboy]

Re: Aperture F readings and Extenders EC14 & EC20

f16 is mighty high and would require ISOs that are at least 800 I guess. If you get along with the combo at f16 then fine but irrespective of the ISO I have found that the best aperture for the 50-200 (old version) plus the Ec20 is f9 and that requires good light at ISO 100. Depends what you are shooting I suppose but I use this combo for wildlife and birds mainly and I would rather keep in the 100 to 400 range if possible. However, I have never been really happy with it in combination with my E-3 and have wondered about getting the EC14 to improve IQ but at the expense of a loss of reach.

Thanks Dave for your experience.

The point I was trying to make is to question the displayed value. f16 is very high using a lens without a teleconverter, but with a teleconverter is it really f16. The lens is the same and do you really believe you can set a value of f45 it is very small! My take is that if you set the aperture to f8 on the 50-200mm lens then add a EC20 it displays a value of f16 the aperture has not changed just the way the camera sees the lens aperture. If I have got that wrong please can someone correct me.

I take your point about high ISO grain but I prefer a sharper image and I will have to execpt the grain when using high ISO's. When using a teleconverter it is always a question of compromise. Only the person taking the picture can decide what it is they want to compromise, its their picture and therefore must be right for them.

The following picture was taken with poor light at an ISO of 2500 yes its grainy but I guess there is software that could clean it up. Its certainly a lot sharper than my takes at f8.


John

[Tordan58]

Re: Aperture F readings and Extenders EC14 & EC20

Hi,

Since you will likely use the lens at max zoom, meaning 2x200 mm, I believe you should aim for shutter times of 1/500 or shorter. (Unless you use tripod).

Let us say light is favorable (sunny with some haze), meaning EV14. You would need ISO 800 to shoot at F16 and that likely means noise. If light overcast conditions you need ISO 1600 and if overcast ISO 3200...

As you write F16 means lens at F8 (and losing 2EV through the EC20). With the 50-200 I don't believe there is a need to use as small apertures as F8 to improve sharpness, the lens performs well starting at wide open.

However it may be wise to increase the depth of field in order to ensure the bird is in focus and to accomodate for imperfections when focusing (AF or MF). The shorter the shorter the distance, the shallower the depth of field. For refererence below are some examples of the depth-of-field for focal length 400 mm. I picked arbitrary distances that you could imagine in a real situation on the field. I stopped at 20 meters, that is where a 20 cm large bird would fill approximately 1/4 of the frame width.

Distance F4.0(*) F8.0
5 meters <1 cm 3 cm
10 meters 5 cm 8 cm
15 meters 10 cm 20 cm
20 meters 20 cm 40 cm
(*) Data for F3.5 was not available. I used F4.0 instead


/Tord

[birdboy]

Re: Aperture F readings and Extenders EC14 &amp; EC20

Hi,

Since you will likely use the lens at max zoom, meaning 2x200 mm, I believe you should aim for shutter times of 1/500 or shorter. (Unless you use tripod).

Let us say light is favorable (sunny with some haze), meaning EV14. You would need ISO 800 to shoot at F16 and that likely means noise. If light overcast conditions you need ISO 1600 and if overcast ISO 3200...

As you write F16 means lens at F8 (and losing 2EV through the EC20). With the 50-200 I don't believe there is a need to use as small apertures as F8 to improve sharpness, the lens performs well starting at wide open.

However it may be wise to increase the depth of field in order to ensure the bird is in focus and to accomodate for imperfections when focusing (AF or MF). The shorter the shorter the distance, the shallower the depth of field. For refererence below are some examples of the depth-of-field for focal length 400 mm. I picked arbitrary distances that you could imagine in a real situation on the field. I stopped at 20 meters, that is where a 20 cm large bird would fill approximately 1/4 of the frame width.

Distance F4.0(*) F8.0
5 meters <1 cm 3 cm
10 meters 5 cm 8 cm
15 meters 10 cm 20 cm
20 meters 20 cm 40 cm
(*) Data for F3.5 was not available. I used F4.0 instead


/Tord

Hi Tord
Thanks for that. I had looked at DOF figures and it seems that they are more of guide that a precise rule as many other factors can come into play.

My question however was not a theory one but a pratical one. Had other members tried using an aperture with a displayed value of F16 when using the EC20 and did they see an improvement?

John