APO extender image quality versus digital crop on M240

[dkCambridgeshire]

Advertisement (gone after registration)

Impressive.

 

dunk

[fernando_b]

This morning I did some test with my new tripod and 400mm Telyt and 2xAPO extender (making it 800mm). My M240 is not with me that's why I did it with Nex-6. The results were perfect and I could see extra details due to 2XAPO that I didn't see earlier with only 400mm Telyt.

 

I tried to compile the results in the picture below. Note that it is pushing the limits. 4.5lb camer+lens on a sub 3lb tripod with 15sec exposure (it was way before dawn. You could still see illumination from street lamp).

 

My guess is that it worked because of "electronic front shutter" of Sony. M240 doesn't have that and will create some shake. You may need to switch off LV after focusing and use the heaviest tripod you have

That is impressive! I couldn't convice myself that a 40 years old lens could produce such an image...

Much depend's on hand vibrations, that you eliminated.

Fernando.

[jmahto]

That is impressive! I couldn't convice myself that a 40 years old lens could produce such an image...

Much depend's on hand vibrations, that you eliminated.

Fernando.

It is. However we should note that this old lens (400mm Telyt 6.8) has enough field curvature causing out of focus from 1/3rd away from the center. It doesn't matter for objects like birds etc but for plane objects it shows softness at the edges and corners. But the center is always very sharp, even with 2XAPO. 

[farnz]

Yes this looks like the enemy of long lenses: vibration.  With the 2x APO-extender on the 280/4 APO-Telyt-R the tiniest vibration causes softness - you can see this through live view even when you think the lens is still and stable when mounted on a tripod.  I have often used the 280 and APO extender and the results are certainly not let down by my extender.

 

The M240's EVF isn't the sharpest tool and I normally use the SL in preference when shooting with long telephotos.

 

Pete.

[masjah]

I agree with Pete - using a 280/4 Apo with a 2X Apo Extender is a challenging exercise. I remember photographing the central tower central ceiling boss inside York Minster - it's about 200 ft up - with this combination. I 'd got an 055 Manfrotto tripod with legs unextended, on the stone floor of the Minster. I'd got the lens and extender mounted on an R9 pointing upwards, and with a right angle viewfinder (which has a 2X magnification option to help focus). I was therefore lying on the floor (as if doing penance). I was using mirror lock-up and time delay to minimise camera vibration. I think I got one out of four or five with good sharpness. Not easy.

[jmahto]

I repeated my test with a much sturdier tripod (Gitzo GT3542 carbon one) with a beafy ballhead. Borrowed from my friend. Although sturdier than my tripod (Q666C), Gitzo still vibrated enough that delay shutter was necessary. I also found that Girzo's center column was equally sturdy (almost no change in vibration settling time with column up or down.), whereas my Q666C's center column was too flimsy. It took around 7-8 second for vibration to settle (as seen 10x live view), whereas GT3542 settled in 3sec.

[jaapv]

Advertisement (gone after registration)

I do find that in many situations a beanbag is superior to a tripod. The reason  - I surmise-  being that a beanbag will reduce the frequency of the vibrations by damping fast movements, whereas a tripod  tries to attain rigidity- never succeeding 100%.

Still, a shutterspeed of twice the focal length is advisable in all cases.

[sls]

I do find that in many situations a beanbag is superior to a tripod. The reason  - I surmise-  being that a beanbag will reduce the frequency of the vibrations by damping fast movements, whereas a tripod  tries to attain rigidity- never succeeding 100%.

Still, a shutterspeed of twice the focal length is advisable in all cases.

 

Good advise. Back to the bird pic, I was using a beanbag. Next trip is to Iceland (March) and have an old cushion cover that I can fill with sand when I get there.