Einreb92 Loc: Philadelphia

I think I could get sharper images, from my rig and am contemplating trying FoCal. I know some of you have and use this, to further dial-in your glass. Can anyone speak to how and if this can be accomplished with a telephoto lens? I have read the information that I can find on their website, but am looking for more "real-world" feedback. I have already sent lens and body to the maker of the lens, but am trying to squeeze a bit more out of my combo. If you are one who feels like it is a waste of time and who would chastise the use of anything but a Nikon lens on my Nikon, please do not bother. Thanks!

CWGordon

I hope we get some good and helpful answers. I could stand
to learn the same thing. I will
keep checking back to see if
we get anything useful.
Thanks for asking.

CWGordon

I hope we get some good and helpful answers. I could stand
to learn the same thing. I will
keep checking back to see if
we get anything useful.
Thanks for asking.

TriX Loc: Raleigh, NC

If you have some specific questions, please let me know, and I will try to address them. The procedure is that after purchasing and downloading the SW, you buy or print a target. You then put the camera on a tripod with the target on a surface that is square to the camera and at the specified distance. You attach the camera to the computer via USB and start the SW. After making the appropriate settings on the camera (lens wide open, single point focus, etc. and covering the eyepiece) you use the SW to accurately point the camera at the center of the target. You 5hen run the calibration. Depending on the camera, the SW will make the settings, or will instruct you via audio and on-screen prompts to make various changes to the microfocus adjustment. The SW will produce a curve of sharpness vs correction curve and you will arrive at best correction which is dialed into the camera, and the camera will recall that calibration whenever that lens is mounted. Finally, you may choose to run the aperture vs sharpness test which will give you an acuity (sharpness) vs aperture curve. It will also give you an absolute value as to the lens sharpness, so you can compare to other lenses and insure your lens is up to snuff.

rgrenaderphoto Loc: Hollywood, CA

So you are building an in camera profile for that specific lens, or is it just informational in nature?

TriX Loc: Raleigh, NC

You are establishing a single MFA correction for a prime lens or two corrections for a zoom (typically one on the wide end and one on the tele) which is stored in the camera and the camera recalls whenever the lens is mounted. It is not as precise at all distances as the multiple corrections that some 3rd party lenses such as the Sigma dock allows, but I have tested it on a single lens on various distances, and it stays very close to correct at all distances, and substantially improved over no correction. Of my 7 Canon lenses plus 3 tested with a Canon TC (5 of which are “Ls”), all but one benefitted from correction, and two would have been too soft to suit me without correction.

CWGordon

...or, I suppose you could ask the guy at your local camera shop. He could probably show you. I am having a similar problem with my newest lens. Not being awfully bright and not always getting how high-tech stuff works; I think that is what I am gonna be forced to do.

TriX Loc: Raleigh, NC

Here are a couple of my threads on FoCal that will show you how the interface and test results look:

https://www.uglyhedgehog.com/t-573232-1.html

https://www.uglyhedgehog.com/t-508300-1.html

ggab Loc: ?

Some newer cameras allow for two MFA corrections, one wide and one tele.
It is quick, either fully automatic or partially automatic, easy and it works.

imagemeister Loc: mid east Florida

To make it simple and not so laborious, I believe you could/should try doing a focus calibration at the longest focal length and at a distance you consider to be in the middle of YOUR most used range - and see how that works for you. f6.3 lenses will have some lee-way as compared to faster f4-5.6 lenses.

IMO, calibrating the shorter focal lengths of a f5-6.3 lens is overkill unless you suspect an unusual problem.
.

morkie1891

I have done the test at both the longest and shortest focal length and then the lengths I most often use with that specific lens. (Found by sorting images in lightroom). I then averaged those results for my final setting. Probably overkill.

morkie1891

I have done the test at both the longest and shortest focal length and then the lengths I most often use with that specific lens. (Found by sorting images in lightroom). I then averaged those results for my final setting. Probably overkill.

MW

By “telephoto” I assume you mean “zoom”. (A single focal length telephoto such as 200m is treated like any
other single FL lens.)
So, a zoom does present a problem. What I did was did was run the calibration three times - at minimum zoom, max zoom and mid point and record the results. Then I picked calibration adjustment that minimized the overall error -ie a compromise solution. An alternative solution in certain cases would be if there is a a particular focal length you use most of the time. Keep depth of field in mind - if you routinely stop down quite a bit the DOF may compensate for the focus error

Einreb92 Loc: Philadelphia

Thanks for the idea, but despite living in a large metro city, the camera stores around here seem more intent on selling and less on teaching and knowledge expansion.

amfoto1 Loc: San Jose, Calif. USA

FoCal does multiple tests for focus accuracy, then arrives at a recommended adjustment.

How useful that will be to you depends to a large degree on the camera you're using.

Not all cameras have a micro focus adjustment feature. For example, among the current Canon models only the 80D and higher models have it... none of the "Rebel" series have it.

Older Canon cameras had means of adjusting up to 20 lenses and only doing a single adjustment per lens. But, worse for some of us, they weren't "lens specific". MFA made lens MODEL adjustments. For example, if you had two Canon 50mm f/1.4 lenses and determined an adjustment required for one of them, it would be applied to both. Now, most people don't have multiple copies of a lens so this is only a problem for a few of us (I currently have two 300mm f/4 and two 28-135s... have had multiple copies of other lenses in the past). What's a correct adjustment for one lens might be totally wrong for another copy of the same lens model. It also wasn't ideal for zooms, since only a single adjustment was possible. You often had to compromise with zooms.

Newer Canon DSLRs really improved on this. The ones with MFA now can be programmed with fine-tuning adjustments for up to 40 lenses, have means of making two adjustments with zoom lenses, and the adjustments are lens-specific (MFA refers to the lens' serial number, to distinguish between and allow different adjustments for multiple copies of any particular lens model).

FoCal recommends that the target be set up at a distance that's 50X the lens focal length.... so for a 50mm lens it's roughly eight feet away (50 x 50 = 2500 and there are just over 25mm per inch, so call it 100 inches, which is 8.3 feet). The problem comes when fine tuning large telephotos. Based on that recommendation, a 400mm lens would require the target be set up 20,000 millimeters... or approx. 800 inches... or roughly 66 feet away! If that's a problem, it may be possible to use 25X the lens focal length... but still requires a lot of space, with the target over 30 feet away.

You can fine tune with MFA without a software like FoCal. What Canon recommends doing is simply focus on a target at a moderate distance using the in-viewfinder focusing array... then switch to Live View and focus on the same target. If the two don't agree.. if the lens changes focus at all with Live View... then there is some adjustment needed. You can experiment with + or - adjustments until repeated testing shows no difference between "normal" and Live View focusing. This is because Live View uses the image sensor itself to focus... so needs no MFA at all. If the "normal" focus agrees with that, it's accurate too.

Or, you could just switch to a mirrorless camera and never have to worry about any of this. That's because mirrorless camera's focus using sensors embedded directly in the imaging sensor itself (just like Live View), so there's never any need to adjust them at all.