Thanks Anita. I do understand the crop factor concept, equivalent focal length, number and size of the pixels, etc. So, a 90mm 2.8 lens on a crop sensor camera is effectively 135, but the widest aperture is still 2.8? Or is it?
YES, APERTURE DOESN'T CHANGE.
I think I get what you and Jerry are saying regarding full frame vs crop sensor DOF:
Here are two quotes from
bobatkins.com: "
The subject of differences in depth of field between full frame and crop sensor images is somewhat complex since it depends on if you use the same lens or diffferent lenses on the two cameras and if you shoot from the same position with both cameras. However you can basically state that for images with the same angle of view (i.e. the same magnification), crop sensor images have a larger depth of field. This may be good for landscapes, but not so good for portraits where you often want a shallow depth of field to blus out distracting background details."
"the bottom line is that if you mount a lens marked "50mm f2" on an APS-C crop camera or a full frame camera, it's f2 on both of them and it's 50mm on both of them. The so called "1.6x digital multiplier" is really a factor which affects the field of view which is recorded and which does depend on format size. It does not affect the aperture and it does not affect the true focal length of the lens."
As a macro photographer (and you are a very good one!:S3:), you often want that shallow DOF, as well as to get close and fill the frame? Won't a full-frame mirrorless camera give you the same DOF as a full-frame DSLR?
I WOULD ASSUME SO. HOWEVER, I'VE NEVER OWNED A FULL FRAME CAMERA, SO MY EXPERIENCE IS LIMITED TO APS-C SENSORS.
I know for butterflies, having a little bit of distance can be good, so that the subject doesn't fly off. As I recall, on the day I shot the Monarch at Mono Lake, it was a warm day and the butterflies were active, so it was an advantage to have that bit of extra 'reach' and not have to approach too close. BTW, When I first got into digital photography, I shot butterflies at f16, 1/250s, with the popup flash on my Canon 20D with a 28-200mm lens on the advice from a guy at the 2006 NABA conference.:w3 Fortunately I know better now, but have never used a true macro lens for butterflies-my favorite lens has been the Canon 300mm f4L IS. The reputed MFD for the Sony 90mm f2.8 is 11 inches from subject to sensor. This is not a lightweight lens, but it is solid and well made, so I think you will like it when you get a chance to use it.
Did you get the Olympus rental and how did you like it?
I DID RENT IT. UNFORTUNATELY, THE LCD SCREEN QUIT WORKING PART WAY THROUGH.
I PLAN TO TRY TO SONY 7II NEXT.