I did not with my examples, but agree it will make a difference. Considering the closeness of the nearest subject in my tests, differences appear minimal.

My final one on this I think............

It was stated within this thread and another that if you use two different focal lengths from the 'same' camera/subject distance the 'perspective' would change. Let's forget the word 'perspective' for a minute and consider another critical 'suggestion' that was made; "You can not superimpose one image taken at one focal length onto another when taken from the same position as the perspectives will be different", I say as well as others, you can.

You have attempted to use my images to disprove this fact, but I have clearly shown your 'technical' method is extremely poor and flawed. Why is it flawed, your lines don't line up with anything credible.

Above you mention "While it is sometimes hard to detect it is there, and sometimes it creates problems".

So here's my last example for you, I tried to find a 'worse case scenario'. I will agree with one thing you have said, "it is sometimes hard to detect", although I would have said just about totally impossible unless you have a method of ensuring 100% that lens distortion is not present at all.

Point a) 720m from camera. Point b) 4900m from camera. Point c) 3.5m from camera. Note the buildings directly under the a, and b,. And for info this time I used lens profile correction in ACR.

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Really ?

I can only assume you have made that assumption based upon the 'accuracy' of the red and blue lines you placed on your attempt to align my two images.

Out of interest, what is the red line that I have pointed out below supposed to be aligned with Bob?

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This statement makes absolutely no sense with respect to 'perspective'.

The 'blur' simply shows where two images of two different sizes and different alignment composed together make the result "blurry".

Yes, you have clearly not aligned them properly. It takes considerable work to adjust both 'physical position' plus 'enlargement' of the image you are placing within the other. You will need to go down to pixel level at times.

Here's another set of two shots, 28 & 75 mm taken with the same lens. Note that the opacity of the 75mm layer I am inserting is set at 50%. Whilst I align I concentrate on two points, in this case the top of the stink pipe and the street light. Again it is windy so take no notice of greenery.

I would suggest any minor anomalies are due entirely to lens distortion, possibly wind on the power lines, or that I could have got it better if I had spent more time on it. To suggest what this may show is a "perspective" change would really be grasping at straws.

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Different lenses are going to have different distortions, whether primes or zooms. Changing lenses adds to the possibility of alignment change (slight movement of tripod). As mentioned in the post, I used the 28-75mm zoom, it was a Tamron.

It would be interesting to see what the results are using 'lens correction profile' as opposed to not using it, I suspect a noticeable difference.

Here are the two images, 28mm & 75mm

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I have seen others do exactly the same previously Bob in their efforts to show what actually happens.

As for the anomalies, disregard the failing wood treatment and concentrate on points where the two frames meet. The images were aligned with lower opacity on the smaller frame and of course the ratio was maintained throughout equalising re-sizing. The subject was chosen specifically because you could 'clearly' see points, bolts, powerline insulators to use to for sizing.

There are obvious very minor anomalies that can be seen, pole edge alignment, power line edge alignment and I put these down to two reasons, a) the fact that manual alignment has to cater for horizontal & vertical movement as well as expansion (diagonal movement) which become difficult with the images expanded on screen. b) that my 28-75 varies in distortion between the range. For info I did not use 'lens distortion correction'.

As for greenery, take no notice of any because it is breezy here.
I can happily post the original shots, but then anyone could say that the result achieved was luck because of distortion in my lens.

I'm new to this forum but have read this being discussed so often.

I have done the picket fence, and all lines up. So here's another one I just did that has very easy reference points within it to assess alignment 'accuracy'. Shot at 28mm and 75mm with 75mm superimposed on the 28mm frame and all lines up, so no change between any points in the image.

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