Lens hood modification for DFA 100mm macro WR when used on full frame

bdery · 09-09-2016, 01:02 PM

Some people on the forum recommended replacing the (mostly useless) hood of the DFA 100mm macro Wr with a simple step-down ring from 49mm to 28mm. This indeed works perfectly on APS-C and I even included it in my review of the lens.

However, on full frame 28mm diameter causes strong vignetting, which is to be expected. I decided to test another ratio, this time selecting a 49-37mm step down ring (these seem ubiquitous on eBay).

Lo and behold, it works perfectly! I ran several tests and could not discern any vignetting whatsoever, even when shooting RAW on the K-1.

So this simple solution can be helpful for K-1 owners who do not want to be stuck with the original hood.

Na Horuk · 09-09-2016, 01:43 PM

Great to hear!
Still, ever after I saw a user here finding out the stop down ring can act as an aperture, I am a bit more apprehensive. You have to check the DoF with and without the stop down ring, because vignetting alone might not be a big enough indicator. If the DoF gets wider with the stop down ring, then you are essentially limiting the aperture of the lens and you no longer have f2.8. 37mm might be big enough for 100mm, maybe even at 1:1 macro, I'm just writing this post for people who like to get carried away and stick on super small step down rings without realizing the possible consequences

**wolfone** · 09-09-2016, 02:17 PM

I like the DFA 100mm macro WR lens hood and find it very useful for shooting under rainy, dusty and backlit conditions.

Simen1 · 09-09-2016, 02:27 PM

I guess this trick should vignette more at infinity focus (where the light rays are parallel) then at close focus (where the light rays comes to a focus quite close to the lens).

bdery · 09-12-2016, 05:02 AM

Originally posted by Na Horuk

You have to check the DoF with and without the stop down ring, because vignetting alone might not be a big enough indicator.

Exposure is exactly the same, so no worries there. I also used the lens extensively over the week-end and DOF is right where it should be.

Originally posted by Simen1

I guess this trick should vignette more at infinity focus (where the light rays are parallel) then at close focus (where the light rays comes to a focus quite close to the lens).

Hum, no, sorry. You always get light from all distances, it's just in focus or out of focus depending on your focus point. The only thing affecting the angle of the incoming light rays is the aperture.

**UncleVanya** · 10-26-2016, 07:40 AM

Originally posted by Na Horuk

Great to hear!
Still, ever after I saw a user here finding out the stop down ring can act as an aperture, I am a bit more apprehensive. You have to check the DoF with and without the stop down ring, because vignetting alone might not be a big enough indicator. If the DoF gets wider with the stop down ring, then you are essentially limiting the aperture of the lens and you no longer have f2.8. 37mm might be big enough for 100mm, maybe even at 1:1 macro, I'm just writing this post for people who like to get carried away and stick on super small step down rings without realizing the possible consequences

Just over 35mm is the minimum opening for f2.8 on a 100mm lens. So in theory the 37mm is probably ok.

09-09-2016, 01:02 PM	#1
bdery Pentaxian Join Date: Mar 2008 Location: Quebec city, Canada Photos: Gallery Posts: 9,357	Lens hood modification for DFA 100mm macro WR when used on full frame Some people on the forum recommended replacing the (mostly useless) hood of the DFA 100mm macro Wr with a simple step-down ring from 49mm to 28mm. This indeed works perfectly on APS-C and I even included it in my review of the lens. However, on full frame 28mm diameter causes strong vignetting, which is to be expected. I decided to test another ratio, this time selecting a 49-37mm step down ring (these seem ubiquitous on eBay). Lo and behold, it works perfectly! I ran several tests and could not discern any vignetting whatsoever, even when shooting RAW on the K-1. So this simple solution can be helpful for K-1 owners who do not want to be stuck with the original hood.

09-09-2016, 02:17 PM	#3
wolfone Site Supporter Join Date: Apr 2016 Posts: 45	I find the lens hood useful I like the DFA 100mm macro WR lens hood and find it very useful for shooting under rainy, dusty and backlit conditions.

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09-09-2016, 01:43 PM	#2
Na Horuk Veteran Member Join Date: Feb 2012 Location: Slovenia, probably Photos: Gallery \| Albums Posts: 11,186	Great to hear! Still, ever after I saw a user here finding out the stop down ring can act as an aperture, I am a bit more apprehensive. You have to check the DoF with and without the stop down ring, because vignetting alone might not be a big enough indicator. If the DoF gets wider with the stop down ring, then you are essentially limiting the aperture of the lens and you no longer have f2.8. 37mm might be big enough for 100mm, maybe even at 1:1 macro, I'm just writing this post for people who like to get carried away and stick on super small step down rings without realizing the possible consequences

09-09-2016, 02:27 PM	#4
Simen1 Veteran Member Join Date: Jul 2009 Location: Tromsø, Norway Photos: Albums Posts: 1,031	I guess this trick should vignette more at infinity focus (where the light rays are parallel) then at close focus (where the light rays comes to a focus quite close to the lens).

09-12-2016, 05:02 AM	#5
bdery Pentaxian Join Date: Mar 2008 Location: Quebec city, Canada Photos: Gallery Posts: 9,357 Original Poster	Originally posted by Na Horuk You have to check the DoF with and without the stop down ring, because vignetting alone might not be a big enough indicator. Exposure is exactly the same, so no worries there. I also used the lens extensively over the week-end and DOF is right where it should be. Originally posted by Simen1 I guess this trick should vignette more at infinity focus (where the light rays are parallel) then at close focus (where the light rays comes to a focus quite close to the lens). Hum, no, sorry. You always get light from all distances, it's just in focus or out of focus depending on your focus point. The only thing affecting the angle of the incoming light rays is the aperture.

10-26-2016, 07:40 AM	#6
UncleVanya Loyal Site Supporter Join Date: Jul 2014 Photos: Gallery \| Albums Posts: 28,404	Originally posted by Na Horuk Great to hear! Still, ever after I saw a user here finding out the stop down ring can act as an aperture, I am a bit more apprehensive. You have to check the DoF with and without the stop down ring, because vignetting alone might not be a big enough indicator. If the DoF gets wider with the stop down ring, then you are essentially limiting the aperture of the lens and you no longer have f2.8. 37mm might be big enough for 100mm, maybe even at 1:1 macro, I'm just writing this post for people who like to get carried away and stick on super small step down rings without realizing the possible consequences Just over 35mm is the minimum opening for f2.8 on a 100mm lens. So in theory the 37mm is probably ok.