size shift when focus stacking

[mikeci]

Hi all,
last week I tried to take a few sets of focus stacking photos. I am using a Nikon D700 w/ a Nikon 105 macro lens shooting in raw on a fixed tripod, mirror lock up and remote trigger. I took a series of 6 to 8 images at f/8 focusing near to far of flowers. d/l to lightroom 3 then exported each group set to photoshop CS5 as "open as layers in photoshop".
At that point I had noticed that the images where not the same size the closer focal point photos were larger. I tried to apply the "blend images together" filter but it didn't work. the final product had what looked like multiple ghosts.
Has anybody run into this problem? Am I doing something wrong? And if so is there anyway to correct it?

thanks,
Mike

[Canon Bob]

The problem that you're encountering is that magnification will increase as the focus is changed towrds the minimum focus distance. To keep the image the same size, you need to set the focus and leave it and then move towrds the subject taking exposures at regular intervals.....a focus rail is very useful to get everything steady.

If my explanation doesn't make sense then ask and I'll try again.

Bob

[mikeci]

Originally Posted by Canon Bob

The problem that you're encountering is that magnification will increase as the focus is changed towrds the minimum focus distance. To keep the image the same size, you need to set the focus and leave it and then move towrds the subject taking exposures at regular intervals.....a focus rail is very useful to get everything steady.

If my explanation doesn't make sense then ask and I'll try again.

Bob

Bob,
thanks for the comeback.
So this problem is common (when you focus stack) w/ all macro lenses not just mine?
If that is so and if I really want to do this I'll have to put a focus rail on my wish list. As I recall they are somewhat pricey for a good one.
Is it possible to resize each image?
Mike

[Canon Bob]

It's an optical property of any lens, not just a macro lens. As the image plane gets closer, the magnification will increase.
Focus rails are a good solution and price/quality certainly vary enormously. I've tried several and settled on a Novoflex Castel Cross-Q for my needs. It's a quite expensive unit but I utilise it with Canon 1srs bodies which are quite tall and raise the centre of gravity a fair bit. Previously, I have used a Velbon Super Mag Slider which was fine with 30D/40D/50D bodies (un-gripped) as they are lighter and lower. You might compare your D700 sizewise with the Canon ones I mention above and see it the Velbon will suit your needs.

Bob

[Canon Bob]

Sorry, I should have explained a little further....

When the "stack" only covers a few mm's, the magnification change is minimal and the sowtware can usually cope......thinking small insects here. Stacking for a flower head may span several centimetres (or more) and hence the change in magnification is much greater (between the closest and farthest exposure)

Bob

[mikeci]

Originally Posted by Canon Bob

Sorry, I should have explained a little further....

When the "stack" only covers a few mm's, the magnification change is minimal and the sowtware can usually cope......thinking small insects here. Stacking for a flower head may span several centimetres (or more) and hence the change in magnification is much greater (between the closest and farthest exposure)

Bob

BoB,
Thanks again,
all the articles I read on stacking none mentioned this problem. I'll check out the two rails and see what would fit my needs and the weight of my camera. first I have to decide if I will use it enough to justify the cost.

Mike

[Thunder_o_b]

Originally Posted by mikeci

Hi all,
last week I tried to take a few sets of focus stacking photos. I am using a Nikon D700 w/ a Nikon 105 macro lens shooting in raw on a fixed tripod, mirror lock up and remote trigger. I took a series of 6 to 8 images at f/8 focusing near to far of flowers. d/l to lightroom 3 then exported each group set to photoshop CS5 as "open as layers in photoshop".
At that point I had noticed that the images where not the same size the closer focal point photos were larger. I tried to apply the "blend images together" filter but it didn't work. the final product had what looked like multiple ghosts.
Has anybody run into this problem? Am I doing something wrong? And if so is there anyway to correct it?

thanks,
Mike

You really should get yourself a proper stacking program. This is the one that I and many others use, it is a very fine product. And there is a free trial.

Zerene Stacker -- The Basics