Comparison test

[benvendetta]

Having discoved the 'Digital Tele-Converter' on my EPL5, I am wondering how it works. I seem to recall reading that the cropped part of the image (200%) is reprocessed rather than being a straight crop such as you might do in PS. Does anyone know about this?

Anyway, as a test earlier this evening, I drove to my local reservoir and took some shots of my car. Two are shown below. The first is my 50-200 (old) + EC20 @ f9, which IMO gives the best IQ for this combo. The second is my 50-200 + the Digital Tele-Converter, also at f9. ISO was 800 due to the poor lighting and the speeds were around 1/30th and the whole setup was tripod mounted using the 50-200 collar. I used the 2 second timer.





I don't know what you think (of course I have had to resize the images) but viewed full size on my monitor I think that the TDC gives a really good account of itself making the EC20 with the 50-200 when paired with my EPL5 redundant. Of course I would have to continue using this combo with my E-3 but with the improved sensor of the EPL5, I cannot see the need.

[Bluegrass Jim]

Re: Comparison test

Hello Ben,
I would say that second one is definitely better, if you look at the bumper where the change of light is on the right side there is much more detail.
Regards Jim.

[gregles]

Re: Comparison test

I have not used the dtc on the epl5 yet but this looks promising

Thanks Dave

[Zuiko]

Re: Comparison test

It seems that the camera does some sort of interpolation with the pixels, I don't know how that compares to resizing in Photoshop, etc. Sound like a technical question for Ian!

[David Morison]

Re: Comparison test

I'm assuming that these were OOC jpegs as the camera will not reprocess RAW which shows up as the full frame with a highlighted crop when reviewed - jpeg does not.

David

[Graham_of_Rainham]

Re: Comparison test

There looks to be a significant difference in Depth-of-Field. The rear tire tread is much sharper in the second image.

I shall have to play with this...

[benvendetta]

Re: Comparison test

I'm assuming that these were OOC jpegs as the camera will not reprocess RAW which shows up as the full frame with a highlighted crop when reviewed - jpeg does not.

David

Yes, they are ooc jpegs.

[benvendetta]

Re: Comparison test

There looks to be a significant difference in Depth-of-Field. The rear tire tread is much sharper in the second image.

I shall have to play with this...

I noticed this too but don't know why this should be the case. The first shot was 400mm at f9 whereas the second was 200mm at f9 with a centre crop. Would this be the reason?

[Zuiko]

Re: Comparison test

Ian - you're needed!

[David Morison]

Re: Comparison test

I noticed this too but don't know why this should be the case. The first shot was 400mm at f9 whereas the second was 200mm at f9 with a centre crop. Would this be the reason?

400mm would definitely have a reduced depth of field compared with a 200mm, which makes it a useful tool when greater dof is important - as long as the IQ is not seriously affected. Of course the dtc would also allow a wider aperture than the optical teleconverted lens which would result in a faster shutter speed or better stn ratio.

David

[Ross the fiddler]

Re: Comparison test

I think the main difference might be in the metering as the raw file remains uncropped, which is all the 2 X is doing (on the E-M5 anyhow) for the jpeg output. If you look at the size of the AF box, it should appear 2 x larger than normal when using 2 x. However, this is useful for smaller framing or better still, for video usage for that extra reach (when we don't have an EC20). The difference here might be from using the EC20 making it a little darker (with a loss of light through the EC20?) at the same aperture setting.

[benvendetta]

Re: Comparison test

Do the em5 and ep5 also have digital teleconverters?

[David Morison]

Re: Comparison test

Do the em5 and ep5 also have digital teleconverters?

EM5 does.

David

[David Morison]

Re: Comparison test

To extend this study a little further I attached the M.Zuiko 75-300mm to the E-M5 and took a couple of shots of our gate from the back door, the first with lens alone and the second using the 2x etc. Both are jpeg with the unmagnified shot resized to give the same magnification. I used just the one optical system to rule out any degradation that could be introduced by an optical TC and to rule out any dof differences. With just these two I think the one with the 2x dtc has just slightly more contrast and sharpness. Of course extensive field tests would be needed to make a final judgement but it does give me enough confidence to at least try. Whether it will give me enough extra detail for birds/bugs etc. remains to be seen:





David

[Daveart]

Re: Comparison test

Hi one other way to test how well the d.t.c works is to take the image the was taken without dtc and 2x crop in Photoshop to see if there is any real benefit to d.t.c, although I have the EM5 a 2x crop the conventional way through photoshop produces excellent results i.e. 16x12 size print with no degradation even using a loupe glass over the print it would appear that it could event go to 32x24 size print before any start of degradation takes place.

Dave