How should I resolve my birding GAS?

User1303423862 wrote:

nnowak wrote:

User1303423862 wrote:

My lovely new EF 70-300 IS II USM lens has arrived.

I've been over to the local duck pond to grab a couple of test shots with Larry's handmade 2X TC at shorter and longer FLs and higher and lower ISOs.

Looking pretty good, though not quite as good as the TC along with the 55-250 lens Larry originally calibrated it to. I'm going to have to roll up my sleeves and try to make one specifically for this lens I think. I already have a Kiron optics 2X in Minolta mount I won off ebay for £4. Now I need a 36mm EF extension tube...

Why do you need to handmake a teleconverter when there are plenty of third party EF options on the market that will directly mount to your EF 70-300mm with no modifications? A very quick search on eBay turned up several options under $50.

They won't work with more recent Canon cameras (unless you remove the printed circuit board from inside them).

Have you tested this on your M6?  I am pretty sure this was only a limitation with the AF system used in the DSLRs that could only work at effective apertures up to f/5.6 or f/8.0.  Even if it is still the case, soldering a few wires to bypass the circuit board is far easier than trying to hand align optical elements stuffed into an extension tube.

Anyway, here are a couple of OOC JPGs.

These look pretty soft and low in contrast with color fringing on the edges of highlights. It would be interesting to see similar shots without the teleconverter in place since these sample were only at 94mm and 200mm respectively.

In my experience, it's pretty hard to photograph swan plumage in full sunlight without blowing out the highlights, so I underexposed the shot with respect to the background.

I was not commenting on the darkness of the background.

I could mask and recover shadow detail, but these are just quick test shots.

The samples are actually at 188 and 400mm respectively (the TC doesn't report its existence to the camera).

Yes, I understand that.  Since your 70-300mm zoom includes 188mm in the range, there was no need for the teleconverter in that image.  Even if the bare lens wasn't sharper (very unlikely), you would have been able to drop your ISO by almost 2 stops.

I would be willing to bet that 200mm plus the 2X converter will look worse than a photo at 300mm and cropped to 4500 X 3000 for the same equivalent field of view.

The acid test will be at 300mm + 2X TC downsampled to compare with 300mm cropped to half resolution to get the equivalent FOV. That's what this is really about.

Start simple and compare 150mm plus the 2X converter versus the bare lens at 300mm.  This will eliminate any variance from upsampling/downsampling and will most clearly show what the 2X converter is doing to the image.  If you need a repeatable target with lots of fine detail, I would suggest a child's stuffed animal.

Whilst you're here, and hopefully looking at a bigger screen this time, please have a look at Larry's TC on the 55-250 IS lens and tell me where in the image I need to be looking for the "significant degradation in image quality" you talked about last time.

The squirrel image looks a bit better than the bird photos you have posted, but part of this is likely due to being at a much lower ISO than most of your other samples.  At 135mm plus the 2X converter, this is another image that could have been easily captured without the teleconverter.  In general, all of the samples have this appearance of being captured through a dirty, hazy window.  If you zoom in, there is just no fine detail due to the degradations from the 2X converter tied with the ISO getting bumped up 2 stops.  It is the difference between capturing "a" photo versus capturing "the" photo.