Issues of Aperture

[Tintin124]

I managed to find that sawfly from the other day shot with the Venus and managed to get it on the MP-E up to 5x mag.

Though with @TimmyG advice about DOF running through my head I shot it a f16 (5x mag) but the results were disappointing now I suspect that the softness is either down to glare (lens hood not used) or diffraction.

Anyone got any suggestions? Best viewed on Flickr

1. f16

IMG_8495 by bthomas124, on Flickr

2. f10

IMG_8498 by bthomas124, on Flickr

3. Aphid ??? 5x

IMG_8469 by bthomas124, on Flickr

4. Oribitad

IMG_8479 by bthomas124, on Flickr

5.

IMG_8503 by bthomas124, on Flickr

6.

IMG_8501 by bthomas124, on Flickr

7.

IMG_8476 by bthomas124, on Flickr

8. Tiny Shiny --- Only seeable through lens.

IMG_8483 by bthomas124, on Flickr

All comments welcome and appreciated.

 

[TimmyG]

Hi Bryn, I would say any loss of sharpness would be down to diffraction. At 5 times magnification on the MP-E I tend to keep aperture to around 8 or lower, increasing to F13 at 1 times. I rarely (if ever) go higher than this.

I suspect glare would cause a loss of contrast, but I'm not seeing that here.

The other cause could be slight camera movement. You aren't allowing much light through at 5x and F16 so you flash will have to fire for longer, but I would think diffraction would be the main culprit.

 

[ChrisA]

Find the Max Mag is hard for sharpness as a whole - for the reasons above. But the F stop definitely needs to be below F9 to stop the diffraction affecting it.

 

[jus_tin]

I tried reversing a 35mm on the end of my Sigma 105mm for abit of extreme macro but that stuffs impossible especially handheld. I dont know what magnification that gave me but i quickly gave up since i didnt really know what i was doing and after googling diffraction i was definitely getting plenty of that!!

 

[GardenersHelper]

I shot it a f16 (5x mag) but the results were disappointing now I suspect that the softness is either down to glare (lens hood not used) or diffraction.

Anyone got any suggestions?

Like Tim says, mainly diffraction I should think.

Effective aperture = Nominal aperture * (1 + magnification)

In this case, Effective aperture = 16 * (1 + 5) = 96.

As you know, I'm keen on small apertures, but my minimum apertures are in the region of f/22 to f/32 in APS-C terms. This equates to about f/5.6 with the MPE at 5x, since 5.6 * (1 + 5) = 33.6.

 

[Tintin124]

Hi Bryn, I would say any loss of sharpness would be down to diffraction. At 5 times magnification on the MP-E I tend to keep aperture to around 8 or lower, increasing to F13 at 1 times. I rarely (if ever) go higher than this.

I suspect glare would cause a loss of contrast, but I'm not seeing that here.

The other cause could be slight camera movement. You aren't allowing much light through at 5x and F16 so you flash will have to fire for longer, but I would think diffraction would be the main culprit.

Thanks mate... I will keep that in mind for future

Find the Max Mag is hard for sharpness as a whole - for the reasons above. But the F stop definitely needs to be below F9 to stop the diffraction affecting it.

Excellent info thanks Chris

I tried reversing a 35mm on the end of my Sigma 105mm for abit of extreme macro but that stuffs impossible especially handheld. I dont know what magnification that gave me but i quickly gave up since i didnt really know what i was doing and after googling diffraction i was definitely getting plenty of that!!

Lol... weren't doing things by halfs then Justin

Like Tim says, mainly diffraction I should think.

Effective aperture = Nominal aperture * (1 + magnification)

In this case, Effective aperture = 16 * (1 + 5) = 96.

As you know, I'm keen on small apertures, but my minimum apertures are in the region of f/22 to f/32 in APS-C terms. This equates to about f/5.6 with the MPE at 5x, since 5.6 * (1 + 5) = 33.6.

Thanks for the technical info I will have to think about maybe stacking in future :nailbiting: