I'm about to buy a 47mm Apo Digitar lens to use on an Alpa XY. Those of you who use this lens for architecture, could you please tell me whether a centre filter is really necessary given its image circle?
Thanks.

No, not at all - at least not with a Leaf back, where the Custom Gain Adjuster easily correct the small amount of fall-off you will find with this lens.

Fantastic lens by the way

best,
Adam

As adam, has indicated, it is not a necessity with several backs included Leaf's current range. Gain / Custom white corrections can make up for a decent amount. However with the ALPA 12 XY, I would assume you will require a significant amount of shift from the system, and the centre filter would be a worthy investment if this is in fact the case.

The logical questions remains.. What back are you planning use with the ALPA 12XY and Schneider 47mm APO-Digitar ?

Regards,

Jordan
DTG

This thread is important for you...

http://luminous-landscape.com/forum/index....topic=20677&hl=

In some cases the centre filter actually causes problems

Murray

Thank you for your answers. I'm working with an aptus 22, and yes, I'll be hoping to make use of the 47mm's full shifting potential...

same answer with a Sinarback and the use of the Brmbaer's eMotion Converter: this software will take care of any lens fall-off, among others, automatically and in a batch-process on as many files you have.

Thierry

Have you used the Custom Gain Adjuster with the Aptus 22?

You may not have noticed (or they might not exist), but there can be some subtle color casts with the Aptus 22 using the wide Digitar lenses. When you get the lens, test the combo with the back in vertical orientation and shift up 20mm. Shoot the white plexi disc that comes with the back or shoot a white uniform surface and make a light gray exposure. There are three things to look for...

1. Color casts in the form of Magenta/Green shifts. The Custom Gain Adjuster (CGA) would remove these casts 100%.
2. A possible center fold line running horizontally through the image at exactly the center of the image running all the way from side to side. The CGA will fix this also.
3. A Red/Cyan shift running from the top to the bottom of the image. This is caused by the light from the lens going through the IR filter in front of the sensor at extreme angles. The CGA will fix this also.

It is good to test these issues so you don't discover them on your first job. Both Rainer with his eMotion 22 and I with my Aptus 22 experienced very subtle shifts in color. Although these color casts are much more prevalent with the 33MP chips, it is still better for you to be safe than sorry.

If you find that you don't have any of these issues, it may be more convenient to use a center filter on the 47 digitar than to shoot the white plexi reference shots and run the CGA for every shot just to remove the light fall-off. If you do have any color shifts, then the CGA does a great job with removing lens fall-off as well. It can even be set anywhere from 1%-100% removal of the fall-off. I most often set it at 50%.

I use the ALPA XY, I had never felt the need for the centre filter for the 47mm, I only use it on the 24mm and 35mm

Adam

I haven't made use of the Custom Gain Adjuster yet, I have been shooting with the 35mm + centre filter and have not noticed any obvious colour shifts, that's what made me wonder about the need for the centre filter with the 47mm...

Well it is subjective and dependent on subject matter. Here is the fall-off of the 47xl with 22mm of shift....

Click to view attachment

Thank you all for your views.