R5+100-500+1.4x or R7+100-500?

Karl_Guttag wrote:

I'm trying to understand your point, and more importantly, I am interested in the image quality difference between the R5+1.4x TC vs R7 on the RF100-500 with no TC. This is of interest is in the common situation that you can't get the subject to fill the frame.

Also, I forgot to mention that to make things equal, there should be a 2x "ISO penalty" for the R5 since it loses a stop for the 1.4x TC.

And-roid wrote:

Karl_Guttag wrote:

I appreciate your posting the comparison, but I can't understand what point you think your comparison makes.

My understanding is that the question is, what is the picture quality if you stand in the same place with the subject at the same distance and you shoot with the R5+1.4x+500mm and the R7+500mm (no TC).

An R5 has 8192 pixels linearly (horz.) where an R7 has 6960) or a linear difference of ~1.36x more pixels per millimeter (8192 / (6960 x 1.6) = 1.359375). Thus with a 1.4x TC, the R5 should have slightly more pixels per millimeter on the sensor for the same size object.

So if you stood in the same place with a 500mm lens on and 1.4x TC on the R5, the image of the label should be slightly larger in terms of pixels at 100% than with the R7 and 500mm and no TC (at least if I didn't make an egregious math error above).

The mitigating factors would then be quality losses of the TC and the "pixel quality" differences between the R5 and R7 pixels.

Well, for a start the 100-500 hangs onto 6.3 until 470mm, so on the R7 470*1.6= 752mm

But that is not what your pictures showed. The first picture (below) shows 500mm on the R7, at F8, 1/1000, and ISO 500.

R7 with RF 100-500 @ 500mm (note that is a shadow from a nearby wire block left side of image)

Using the R5 and the RF 100-500 with no TC resulted in 3000 pixels on the label

The picture above shows 700mm with the 1.4x on the R5. Since the subject/tag is so much smaller, it must have been taken from much further away or scaled in post.

Additionally, EXIF shows the ISO is 5x more than in the R7 picture as the shutter speed has also been changed. The EXIF says 700mm, f10, 1/2500, and ISO 2500. There will be a 1.4x DoF difference, but something has to give a little (and won't make a big difference on mostly flat target. There are so many variables being changed that it is hard to tell what is going on with the images.

I'm trying to keep it simple. Shoot from the same place with the same shutter speed, have the aperture 1.4x more due to the TC, and double the ISO for the R5 with the 1.4x TC. That is what people would most likely be doing if a small subject is too far away.

All pictures were shot from the same location.   The label is very small and more than one hundred feet away.

This is a a extreme case of cropping and probably more than the average crop that I would usually try.   I did this to show any differences more clearly.