Works for me - great oof background, bags of detail in the fly, and superb soft lighting (no doubt a consequence of your early rise!). Nice one!
Posted by David Sewell on June 28, 2010 at 3:54 PM
I suppose the other David's comment begs the question, did you have a front cover in mind? If you just wanted a portrait format shot, then I think you have a superb one here.
I agree that a bottom-left to top-right diagonal would be better and that like this, the subject looks like it is toppling over a bit, but we can't always get nature to cooperate fully.
What I see from a technical perspectve though is rather more troublesome. You are getting good resolution fron the 50D, but the aperture selected takes you way beyond the resolving capabilities of the sensor. You really don't want to be stopping down any further that f11 with the 50D (or the 7D for that matter) otherwise the image starts to loose too much sharpness due to refraction at the sensor-well level and this is evident in this shot. There is also rather a lot of chromatic aberration (cyan fringe) evident around the fine white hairs on the head and thorax. This is related to the refraction problem but may be mitigated in processing, although in this instance the fringing appears so substantial that I doubt that you will be able to remove it all.
I hope this doesn't sound too negative. It is meant to help you get a better image next time.
It is fine Heath... As I have said before Diffraction (not refraction) is not the problem with digital as it was with film... I will often use f16 with a 50D... I am going to say that the slight 'softness' here is caused by using the 1.4 extender, although it can help to increase the mag very slightly and I have done the same in the past, you will get better results with just the straight lens....
As for comp I do agree that the diagonal is the wrong way, it certainly would have helped to compose in camera with the subject heading towards the top right, for presentation here the size in the frame is right, ignore all this front cover mumbo jumbo...
Looks near enough to me Heath.
By the way we don't all gear our shots for publication. The picture editors do the cropping most of the time anyway.Don't suppose many mags would need a robberfly for a cover
Good stuff.
JR
Well I expected by the title to see someone I know
Nice shot Heath. Good detail but I would take Phil H's advice on board. I think he knows what hes talking about (unlike some others)
Look good to me on the tech front and you have some great detail here. Nit re comp has been covered and I would also add that I find the stem competes with the subject on this occasion not much you could do about it unless it was being cooperative and you could entice it onto something else..?
From time to time I guess we are all guilty of not explaining ourselves fully in short, text-based communications. And I wouldn't normally bother to respond to Phil Hurst's comment above, but since some other people seem to be "having a go", I thought I would try to clarify my take on the technical issues associated with this image.
I do feel that refraction, not diffraction, is the main problem here and Phil also alludes to this, but doesn't follow it through, when he says that he thinks the softness is due to the use of a teleconverter. This is also my view: the reduction in image sharpness is due in my opinion to refraction at the additional lens surfaces in the optical path created by the teleconverter. The evidence for this is in the blue/cyan fringing that I refer to in my earlier post.
Where I depart from the advice given by Phil H is in relation to the best choice of apperture. Phil is of course correct in his view that f16 is usable with APS C-type sensors, but it is undeniable that with very small sensor sites diffraction does limit focusing accuity due to the size of the Airy Disk impinging on the sensor. For best sharpness (as opposed to slightly more depth of field) therefore is it better to keep the size of the Airy Disk closer to 2x the size of the pixel size. Although the 50D is theoretically diffraction limited somewhere between f7.1 and f8, in practice, there is no loss of focusing accuity that I can distinguish at f11. I can however see loss of critical sharpness at f13 and it is evident at f16.
So that is the basis on my advice to Heath. Photography is always about making compromises; compromises between digital noise and ISO, between shutter speed and aperture and also between increasing depth of field and decreasing focusing accuity due to diffraction.
Fair points and thanks for explaining further, hope it didn't appear that I was having a go... I was just trying to point out that, as you rightly say, the converter was the main culprit, and yes you are correct there is a slight loss of critical sharpness when one stops down to f11 and smaller, but this slight softening can be overcome with careful use of capture sharpening, something we could not do when we shot film and had to check for diffraction on the aerial image and then open up slightly from where it set in.
I was just trying to point out that this misinformed idea that a camera is diffraction limited at such and such an aperture and that you should not go beyond that is just not completely true... I am not talking technically here but from nearly 30 yrs experience of working with macro and high macro up to 60x mag....
Thanks everyone for all the comments, in particular the advice on the use of t/c's, CA and refraction. This is one area that I have read alot about, but not really fully understood and I think it probably explains a couple of things in some of my images that I could not quite put my finger on.
Not sure what the publication comment was about, I didn't intend this for publication, mind you, it might look good on the front page of a banking publication! Anyway it seems to have gone now.
Thankfully I took quite a number of shots of this fly so I can play around with the images further, particularly with regards to the composition.
Hope to get some more of these and will be taking these comments into account when I do.
Discussion
14 repliesI would be grateful for some comment, critique on composition and whether this just works or not
Stats:
Canon EOS50D
Sigma 180mm + 1.4xtc
Tripod
Live View - remote release
ISO100, f16, 1/5 sec
processed in Lightroom with a little cropping and PS for web conversion.
Heath
David
What I see from a technical perspectve though is rather more troublesome. You are getting good resolution fron the 50D, but the aperture selected takes you way beyond the resolving capabilities of the sensor. You really don't want to be stopping down any further that f11 with the 50D (or the 7D for that matter) otherwise the image starts to loose too much sharpness due to refraction at the sensor-well level and this is evident in this shot. There is also rather a lot of chromatic aberration (cyan fringe) evident around the fine white hairs on the head and thorax. This is related to the refraction problem but may be mitigated in processing, although in this instance the fringing appears so substantial that I doubt that you will be able to remove it all.
I hope this doesn't sound too negative. It is meant to help you get a better image next time.
As for comp I do agree that the diagonal is the wrong way, it certainly would have helped to compose in camera with the subject heading towards the top right, for presentation here the size in the frame is right, ignore all this front cover mumbo jumbo...
Hope this helps
Phil
By the way we don't all gear our shots for publication. The picture editors do the cropping most of the time anyway.Don't suppose many mags would need a robberfly for a cover
Good stuff.
JR
Nice shot Heath. Good detail but I would take Phil H's advice on board. I think he knows what hes talking about (unlike some others)
Dale
Brett
I do feel that refraction, not diffraction, is the main problem here and Phil also alludes to this, but doesn't follow it through, when he says that he thinks the softness is due to the use of a teleconverter. This is also my view: the reduction in image sharpness is due in my opinion to refraction at the additional lens surfaces in the optical path created by the teleconverter. The evidence for this is in the blue/cyan fringing that I refer to in my earlier post.
Where I depart from the advice given by Phil H is in relation to the best choice of apperture. Phil is of course correct in his view that f16 is usable with APS C-type sensors, but it is undeniable that with very small sensor sites diffraction does limit focusing accuity due to the size of the Airy Disk impinging on the sensor. For best sharpness (as opposed to slightly more depth of field) therefore is it better to keep the size of the Airy Disk closer to 2x the size of the pixel size. Although the 50D is theoretically diffraction limited somewhere between f7.1 and f8, in practice, there is no loss of focusing accuity that I can distinguish at f11. I can however see loss of critical sharpness at f13 and it is evident at f16.
So that is the basis on my advice to Heath. Photography is always about making compromises; compromises between digital noise and ISO, between shutter speed and aperture and also between increasing depth of field and decreasing focusing accuity due to diffraction.
Fair points and thanks for explaining further, hope it didn't appear that I was having a go... I was just trying to point out that, as you rightly say, the converter was the main culprit, and yes you are correct there is a slight loss of critical sharpness when one stops down to f11 and smaller, but this slight softening can be overcome with careful use of capture sharpening, something we could not do when we shot film and had to check for diffraction on the aerial image and then open up slightly from where it set in.
I was just trying to point out that this misinformed idea that a camera is diffraction limited at such and such an aperture and that you should not go beyond that is just not completely true... I am not talking technically here but from nearly 30 yrs experience of working with macro and high macro up to 60x mag....
All the best & no offence meant....
Not sure what the publication comment was about, I didn't intend this for publication, mind you, it might look good on the front page of a banking publication! Anyway it seems to have gone now.
Thankfully I took quite a number of shots of this fly so I can play around with the images further, particularly with regards to the composition.
Hope to get some more of these and will be taking these comments into account when I do.
Heath
An interesting subject and any nits well and truely covered. Looking forward to more.
Cheers,
Lewis.